Frequently Asked Questions (FAQs)

1. You need a Windows 10 OS Release 1607, Build 14393 or higher (Windows 7 or an earlier version will not work)

2. The internal Bluetooth driver is not current and needs an update; check the webpage of the Bluetooth module manufacturer for the latest version

3. Your PC does not have a built-in Bluetooth module, use an external one, we recommend Delock USB Bluetooth Adapter V4.0 dual mode or try other adapters supporting Bluetooth Low Energy (Windows 10 OS required)

Click on “Click for available actions…” next to the level or depth to water measurement (M1 on top), you will be asked to calibrate which allows you to enter the reference value.

This compresses the data file and reduces the size by a factor of up to 10 which is beneficial for a shorter transmission and less power consumption. The data will need to be decompressed (unzipped) on the receiving server. OTT Hydras 3 does this automatically.

Maintenance windows are not available anymore because a dial in via a modem (CSD) is not possible anymore. This is not supported by 4G (LTE) and will be or is already discontinued for GSM/GPRS by the most providers as well.

You need to have a Hydras 3 version 4.0 or higher to have ecoLog 1000 management network support.

The ecoLog 1000 does not have a webserver and can therefore not be reached via a static IP address. The device is a web client only. To have 2-way communication, the network management software OTT Hydras 3 net is available.

“Refresh Status” refreshes the view, reads and displays the last stored values from the ecoLog 1000 as configured in M1-M5. “Measure All” performs an actual measurement and displays these values.

The ecoLog provides two transmission and therefore two transmission times. For each transmission, two servers can be configured as either parallel transmission or fallback.

You can use HTTPS TLS 1.2 (incl. latest Cipher Suites). The ecoLog 1000 does not support FTP-S or SFTP.

Once a station is created and saved in LinkComm, all modifications are automatically saved. An additional step to save changes is not required.

Each electronic device with an internal clock has a time slip called drift. This means the time of the clock is drifting away from the true time. Even though the ecoLog 1000 RTC (real time clock) is quite accurate, it will drift. With SNTP (Simple Network Time Protocol) each time a transmission is done the time is checked on a public server and adjusted if required, this is a no-cost service.

If data is sent to software like Hydras 3 net, the station location will automatically be displayed on the map.

You can do this manually via “Upgrade” in the tab “Diagnostics”. If you receive a new LinkComm, the new firmware for the device is already built into LinkComm and can be installed out of LinkComm.

LinkComm is a free of charge operating software for the ecoLog. The Windows 10 PC version is available on the OTT HydroMet website. The APPs for Android or iOS can be downloaded from the APP stores.

There is only one LinkComm which is used for all loggers including the ecoLog 1000. Make sure to have the latest version with all the loggers supported.

With this you can send a SMS to the ecoLog 1000 and change some parameters (e.g. transmission interval). Details can be found in the ecoLog 1000 manual.

Always save an export of the configuration, the diagnosis file “Diagnostics” -> “Save Diagnostics…” and the “Event log…” (select the hamburger button on the left top to access this) and send these files with the description of your problem to Hydro service. Please be as specific as possible.

If the power source is disconnected longer than 40s, the internal clock loses its time and needs to be set via LinkComm.

Go to “Diagnostics” to find the button “Reset PBAT”.

No, the data is in nonvolatile storage and will remain there even if no power is applied. If the battery is too weak for transmissions, it will stop transmitting but has enough reserve power to continue to measure at least another ten thousand values. Measurement data will not be lost and with the continued measurements the exchange of the battery can be planned. After installing a new battery, the data not previously transmitted will be transmitted and no gaps will occur on the server.

You can set limits to the “Supply Voltage” M3 or the “Power Consumption” M4 and send alarms to one or more recipients.

OTT HydroMet provides a calculation tool helping to understand how long the battery could last.

You can source it only at OTT HydroMet. The whole system is tested and certified with OTT HydroMet components and only in this way we can guarantee the safety and functionality of the device.

The one towards the top (labeled BLE) is green if the Bluetooth connection is active. The second one is for the mobile communication (labeled STAT) is red when a transmission via the modem is active. Additionally, this LED flashes red once after a new start i.e. power reset. You can use this when you are in the office and want to see what is currently going on.

Use no tool. It is sufficient and recommended to tighten the connector by hand.

One desiccant is for the capillary in the cable and one for the housing. We recommend changing them regularly. See the manual for more details.

There are inexpensive adapters from Nano or Micro SIM to the required MiniSIM available in almost every electronic shop.

Data pull via modem is not possible any longer. This is not supported by 4G (LTE) and will be or is already discontinued for GSM/GPRS by the most providers as well.

Yes, both systems can run in parallel on different servers and with different transmissions.

If there is no 4G coverage the ecoLog 1000 will automatically connect to 2G (GSM/GPRS). If 4G/2G coverage is not available, LTE-M may be. The coverage for the LTE-M network is often times better and may be available at your monitoring site.

No, it is a different module with different electronics and interface.

The following parameters can be measured / detected with the OTT ecoLog 1000: water level (through pressure), water temperature, supply voltage, power consumption, signal strength (humidity in com unit not as parameter but as Meta data in OTTML header).

No, it's not possible to connect further sensors, because the OTT ecoLog 1000 is a complete system, which allows only sensors from OTT ecoLog 1000 to be connected.

The ecoLog 1000 is a device that features mobile/cell communication. An option without telemetry is not planned. If telemetry is not needed, the OTT Orpheus Mini is an excellent option for recording water level and temperature values in a compact logger without a built-in modem.

OTT ecoLog 1000 is an IP capable data logger acting as a web client. Web server functionality does not make sense in this device because the modem would need to be powered at all times which would significantly increase maintenance requirements.

LTE-M is a low power transmission option and allows users to access real-time data across greater distances. The low power nature of the LTE-M protocol enables longer battery life of the ecoLog1000. Additionally, the cost of data transmission is low with inexpensive machine to machine (M2M) communication. You can expect to experience better network availability, even underground, and avoid high network traffic in emergency events, such as flooding.

The ecoLog 1000 is intended for cell communication only and does not support satellite transmission. OTT HydroMet offers other solutions, such as the XLink dataloggers for satellite transmission.

The idea behind transmission technology is to push the data, meaning that the data logger has a self-time transmission to a server, so the data is not pulled, but it’s pushed. The advantage of this is that the logger can do this on its own, you don’t need to have the modem on all the time or wait for someone to pull the data. By pushing it, it saves time, battery power, and energy, and with the action and alarm management, it’s possible to adjust, for example, the transmission interval from maybe once per day to two times a day. The XLink dataloggers have the ability to pull data with additional effort.

Very easily. The ecoLog 1000 sends the data to an Aquarius FTP server in a .CSV file. From there, the software ingests the data and visualizes it. Dataloggers can be configured to send information to up to four different servers, one being Aquarius, others being a Flood Warning Service or a government database. This allows your data to be available in various locations. Once the data is in Aquarius, you also have the option to export the data to share with other stakeholders.

There are 2 preferred devices that are recommended by SUTRON.

• USB-to-Serial Converters using the Prolific Chipset have been tested and work consistently with SUTRON Loggers and other devices.
• The KeySpan USA-19H USB-to Serial Converter is also recommended. It has a well-tested history with SUTRON products and comes with a utility that allows you to configure it for any Serial Port number available on your Laptop/PC.

The original Satlinks and Satlink2 will still operate in the GOES system until at least 2026. There is no conversion recommended since the main circuit board would require replacement and costs that would be about the same as a replacement. Plus, with a replacement you get a three year warranty.

The SUTRON Satlink currently manufactured is the Satlink2-V2. The Satlink2-V2 is designed to keep accurate time so that it can continue to transmit for 30 days without a GPS time update. Satlinks and Satlink2s manufactured before May 2011 can transmit for 17 hours without a GPS time update.

The software can be downloaded for either MAC OS X and PC. SUTRON LinkComm software is used to easily set up and maintain data from numerous OTT HydroMet loggers.

Connection is either via direct USB connection or remotely over cell, Iridium satellite, Wi-Fi, or Bluetooth. The software runs on Windows PC, iPhone/iPad, and Android platforms enabling seamless connection with commonly used devices.

LinkComm software is complimentary and used to easily set up and maintain XLink and Satlink dataloggers, as well as the ecoLog 1000, an all-in-one water level logger. LinkComm can be downloaded from our website and in the App Store.

Field exchangeable plug and play modem cards allow for easy upgrade of cellular/telecom technologies including 4G, and cellular IoT (CAT-M1/LTE-M). The XLink 100 & 500 also support Iridium Satellite communications.

The XLink 500 supports Python scripting and has additional analog sensor inputs.

The LTE-M network is a low-cost option with improved network availability. By equipping a datalogger with a modem, a user can leverage the two-way communication features to change configuration and check station status.

An ISE is an Ion-Specific Electrode. It converts the activity of a specific ion dissolved in water to an electrical potential.

The ISE sensors are best suited for spot monitoring activities. These sensors drift more than other sensors and are not well-suited for long-term deployment. Do frequent QA/QC and calibration on ISE sensors, especially ammonium and nitrate, if they are to be used for extended deployment.

Ammonium and Nitrate sensor tips will last from three to six months whether they are stored on a shelf or installed in a sonde. Chloride sensor tips may last a year or more in the same conditions.

Maximum of 49 meters (160') for all ISE sensors. If deployment exceeds 15 meters (49'), the ISE sensor must be removed and a dummy plug (included with sensor) must be installed in the sensor adaptor or the sensor will be damaged.

Use Ammonium and Nitrate sensors in fresh water whose specific conductivity is less than 1000uS/cm. Sodium is a major interference for Ammonium and Chlorate ions are major interferences for Nitrate activity. Chloride sensors suffer interferences when the concentrations of bromide, iodide, cyanide, silver, and sulfide ions are much higher than the chloride ion concentration.

• Rebuild the reference if needed, and calibrate conductivity and pH before calibrating any ISE sensor.

• Calibrate ISE sensors with standards that either bracket your expected measurements or that are close to what you expect to measure.

• The ISE sensors need frequent maintenance and calibration compared to other water sensors. ISE calibrations do not last as long and will drift faster. Bio-fouling and water conditions will affect maintenance and calibration frequency. A difficult to calibrate ISE sensor indicates that it needs to be replaced.

• Before calibrating a new sonde with ISE sensors, soak the sensors in the calibration cup with a high conductivity standard, like 47.6 mS/cm, for 2 to 4 hours to condition the reference electrode. When the reference mV is stable, it is ready.

• Soak a new ISE sensor in any of its standards overnight to condition it. It will calibrate more easily.

• To calibrate an ISE sensor reliably will take a minimum of 20 minutes per sensor. ISE sensors need more time to stabilize than other sensors during calibration as well as during measurements in the field.

• For best results, calibrate the ISE sensor at or near the water temperature it will be sampling. In any case, be consistent in your calibration temperatures.

• When calibrating sensors, it is important to use deionized (DI) water to rinse between calibration steps.

• If at all possible, use a stir plate to calibrate ISE sensors. Keeping the standard well-mixed improves calibration stability.

• When installing, be sure to calibrate pH and conductivity first and then ISE sensors as a best practice.
• Sensors work best in flowing water. We recommend choosing a site in a location with good water flow to ensure movement of water over the sensor.
• After placing the sonde in the water, allow several minutes for the sensors to stabilize for consistent measurements.

Maintenance of the reference electrode is critical because ISE potentials are measured with respect to the reference electrode.

We recommend using a stir plate, if you have one, during calibrations as a best practice to ensure an equalized standard.
Constantly stirring ensures a set consistency for the liquid.

HYDROLAB measurement solutions provide these benefits:

• Ruggedized ISE sensors operate to depths up to 49 meters (160')

• Automatic calculation of Ammonia and Total Ammonia concentrations

• User-serviceable reference electrode

• As well as HYDROLAB’s application advice from the customer support team

Ammonium

• Range: 0 to 250 mg/L-N

• Accuracy: +/- 10% or +/- 2mg/L-N, whichever is larger

• Temperature range: 0 to 40 °C (non-freezing)

• Not recommended for measurements less than 2mg/L-N

Nitrate

• Range: 0 to 250 mg/L-N

• Accuracy: +/- 10% or 2mg/L-N, whichever is larger

• Temperature range: 0 to 40 °C (non-freezing)

• Not recommended for measurements less than 2 mg/L-N

Chloride

• Range: 0 to 18,000 mg/L

• Accuracy: +/- 10% or 5mg/L, whichever is larger

• Temperature range: 0 to 50 °C (non-freezing)

• Not recommended for measurements less than 2 mg/L

Ammonium:

• Can suffer interferences from other ions, especially sodium, potassium, and magnesium. These can reduce your accuracy.

• Specific conductivity of less than 1000 uS/cm.

Nitrate:

• Can suffer interferences from other ions, especially chloride, bromide, bicarbonate, perchlorate, nitrate, and chlorate. These can reduce your accuracy.

• Specific conductivity of less than 1000 uS/cm.

Chloride:

• Can suffer interferences from other ions, especially bromide, iodide, cyanide, silver, and sulfide. These can reduce your accuracy.

Ammonium (NH4+) and nitrate (NO3-) are ionized forms of nitrogen. Nitrate is related to ammonia in that bacteria colonies convert ammonia and ammonium to nitrite and then to nitrate. This final nitrate stage is the least toxic to water life. Ammonia has two forms - the ammonium ion, and the unionized, dissolved ammonia gas (NH3). The form depends on pH, with ammonium predominating when the pH is below 8.75, and ammonia  redominating above pH 9.75. Total ammonia is the sum of ammonium and ammonia concentrations. Ammonia is very toxic to water life, ammonium is less toxic.

Chloride ion concentration is also measured with a chloride ion-selective electrode (ISE). The chloride ISE is a pellet of silver chloride in direct contact with the sample water. Because silver chloride has extremely low solubility in water, the silver chloride pellet never reaches chemical equilibrium with the sample water. Instead, a small amount of chloride ion dissolves into the sample. The resulting relative surplus of silver ions at the surface of the pellet creates a measurable electrical potential that varies with the concentration of chloride ions in the sample. This activity is compared to an electrode filled with a Potassium Chloride and Silver Chloride electrolyte (KCl and AgCl) which has a known ionic activity constant. The difference between these two “half cells” gives electrical potential in millivolts (mV).

Chloride sensors suffer interferences from other ions, working best when the concentrations of bromide, iodide, cyanide, silver, and sulfide ions are much lower than the chloride ion concentration.

Notice that ISEs are sensitive only to the ionized form of the chemical in question. Un-ionized forms of the chemical (for instance, insoluble salts or organic compounds), will not be detected by the ISE.

The chloride ion does not react with, or adsorb to, most components of rocks and soils, and so is easily transported through water columns. Thus, chloride is an effective tracer for pollution from chemicals moving from man-made sources into natural water bodies, or for salt water intrusion.
Applications for Chloride ion measurement include monitoring landfills for leaks, tracing the movement of point or non-point source pollutants within a natural water body (for instance, storm water runoff), monitoring estuary waters for changes in salinity, and detection of salt water intrusion into drinking water supplies.

In case the path length has been set incorrectly during the installation of an LAS scintillometer, WINLAS can correct the C_n² data.

In order to do so, please use the following procedure.

Step 1: 

After entering the relevant info in the parameters section, enter the path length setting set with the potentiometer of the LAS receiver in meters and enter the correct path length in the input field below.

Select OK

Step 2:

Select ‘Run…’  in the WINLAS file menu.

Result:

WINLAS will now process the ScintillometerC_n² data using a correction algorithm for the actual path length.

Theoretical background

WINLAS corrects the path length in the following way:

Using the following equation to derive the intensity fluctuation data from the recorded C_n² values calculated by the LAS using the incorrect path length setting.

(Wang et al., 1978)

The equation is re-written to yield the variance of the intensity fluctuations:

And finally re-calculate C_n² with the correct path length:

Once the LAS has been installed and properly aligned the Path Length dial knob at the receiver control panel must be set for the correct distance between the transmitter and the receiver. The Path Length dial knob has 10 turns maximum with a vernier counter and a locking mechanism.

These graduations are NOT in units of distance! The precise path length must first be converted to a dial knob setting (Pot) using the following relationship for the LAS. The equations below can be used to find the correct Potentiometer setting as a function of pathlength for the LAS and X-LAS.

In addition you can use the calculation tool below to calculate the correct potentiometer setting for the (X)LAS.

LAS:

X-LAS:

LAS MkII or XLAS MkII (includes transit case)

Plus two 12 VDC power supplies (CVP1 LAS MkII power supply x2), and for mounting, two tripods (heavy duty tripod package x1) or secure mounting structure, if required.

LAS MkII or X-LAS MkII (includes transit case)

Meteorological sensor kit

Plus two 12 VDC power supplies (CVP1 LAS MkII power supply x2), and for mounting, two tripods (heavy duty tripod package x1) or secure mounting structure, if required.

• Surface energy balance / radiation budget studies

• Validating satellite data / ground truth

• Weather forecasting

• Irrigation / water management (shortage) - evaporation from rivers, crops and water storage

• Hydrology

• Micro-meteorology / turbulence studies

• Land-atmosphere exchange / boundary layer meteorology

• Agriculture, forestry, Biology, plant evapotranspiration, plant interactions and geosciences

• Forest fire warning

• Optical propagation conditions

• Turbulence, including defense and laser propagation

• No absolute instrument calibration is needed

• Low maintenance, no moving parts

• Low power consumption

• Integral data logging

• Remote measurement:

• Path-averaged Cn2 measurements up to 4.5km

• Representative for large area

• Comparable to grid box size of numerical models and pixel size of satellite images

• No structure / tower influence on measurements (spatial weighting function / no flow distortion by instrument). A tower, building or valley sides can be used to gain height, and they (the support structure) has no or little effect on the measurements as the LAS responds more strongly to the middle of the path and not at all at the ends.

• Easy installation - Can measure over terrain which is difficult to access, or which you do not want to disturb.

• Does not disturb the measurements and measurement area (such as a protected wildlife area).

• Rapid measurements:

• Allows study of fast processes, such as plant transpiration and canopy resistance, which change on a timescale of a minute with changing solar radiation and clouds

• Point measurements (alternative methods to LAS)

• Eddy-Covariance method (need averaging of at least 30 minutes to catch all the eddy sizes. Measures the inner scale of turbulence i.e. the momentum flux, so can be combined with gas flux measurements easily)

• Bowen-Ratio Energy Balance method

• Flux-profile method (MOST)

• Results extremely localized

• Influence of structure / flow distortion

The LAS MkII Large Aperture Scintillometer provides continuous measurements over path lengths from 328 feet up to 2.80 miles. It is the only scintillometer currently available with a built-in display and control-pad. It has internal digital processing to make calculations in-situ and to store data and results. Measurements are on a comparable scale to the pixel size of satellite instruments, making LAS MkII ideal for ground-truthing applications. The LAS MkII is convenient to use due to low power consumption, integrated data logger, accurate reference time from GPS, and works reliably in cold environments.

The advantages of the LAS MkII are the following:

• Low power consumption due to the use of single LED and good collimation of the beam so little light is thrown away. This makes it practical for use with solar panel / battery electrical supply in field applications.

• Contains an integrated lens heater to avoid freezing of the instrument or condensation on the window, and provides good data in cold environments.

• More compact design with integrated datalogger, display and setup buttons which allows the configuration of the LAS without the need of an additional computer and cables / power supplies, and nothing needs to be taken apart. This makes transport and installation much easier.

• Direct connection of the meteorological sensor kit to the receiver instead of to a separate interface or data logger.

• Operates over the full data range of C_n² of 1x10^-17 to 1x10^-11 (= 6 orders of magnitude).

• The transmitter (as well as the receiver) can be tilted to align for optimum signal gain, and minimal power usage.

• A supplied GPS antenna, mounted on the receiver, results in very accurate time from the satellites of the Global Positioning System, logged with the measured data.

• The complete LAS MkII system is shipped in one rugged aluminum transport case, which can be used in the field to store equipment, if needed, as the case is waterproof. Lined with custom fitted foam, it protects the LAS instrument from repeated shocks of 10 to 20g without losing calibration or alignment.

• A certificate is supplied with each instrument detailing a calibration against a reference instrument, performed outdoors for two weeks at the factory.

• A large aperture scintillometer (LAS) has less saturation problems compared to a laser scintillometer, or one with a smaller beam diameter, and so can be used over longer distances.

Yes you can, but there are a few points you have to consider as the analog data output has changed in format.

See appendix H of the latest manual, for details of the conversion of the analog voltage output, UCn2. Note, the manual is written for the improved LAS MkII with GPS, so there will be differences in the hardware, and there are a couple of data formatting issues that are different (voltage ranges).

Most likely the format of your UCn2 data is incorrect for the latest version of Evation, as the software was developed to work with the LAS MkII, which has a different analogue voltage output (positive instead of negative).

For the LAS MkI, the Cn2 voltage output, UCn2, is output as -5 to 0V, where:

  -5V analogue voltage output is equivalent to a Cn2 of 1 x 10^-17  [m-2/3]

   0V is equivalent to 1 x 10^-12 (m^-2/3)

Cn2  (m^-2/3) = 10^(-12+ UCn2)  (this applies to the LAS150, not to the LAS MkII !)

To derive fluxes of sensible heat (H) from the LAS measurements (C_n²), one needs to know the height of the LAS beam above the ground, also known as the effective height. Because the flux is almost linearly related to the height it is important to determine the effective height as accurate as possible (see Appendix F of the LAS manual). Over flat terrain it is relative easy to determine the LAS height: take the average of the height of the transmitter unit and receiver height (i.e. the height between the center of the beam and the ground).

Over non-flat terrain it is a bit more complicated, because now we also need to consider the path-weighting function of the LAS. This weighting function reveals that the center of the LAS path contributes more to the measured C_n² data, than near the transmitter and receiver units. This calculation is easily done by using the effective height calculator built-in to the Evation software, which takes care of the weighting function.

Note: for very long path lengths (> 3 miles), such as when using the XLAS it is also important to consider the earth’s curvature (decreases the height in the center of the path by approx. 6.5' over a path length of 6.2 miles.

More detailed information of deriving the effective height of scintillometers over complex terrain and the effect of atmospheric stability on the effective height can be found in: Hartogensis et al., Derivation of an Effective Height for Scintillometers: La Poza Experiment in Northwest Mexico, Journal of Hydrometeorology, 2003.

Yes, the LAS transmitter and receiver unit can be placed inside behind glass or Perspex windows, preferably at normal incidence to minimise light loss and refraction of the beam. However, it must be noted that windows absorb a fraction of the light beam (~8 to 25%) thereby limiting the maximum path length of the LAS or XLAS.

An error in the path length L of 1% results in an error of 3% in C_n² (and thus H). This shows that the path length should be determined accurately.

The effective height or height of the LAS beam should be measured to 1 cm (a tape measure can be used for this).

The measurement principle of the LAS is based on the scattering of EM radiation by the turbulent atmosphere that result in fluctuations of the intensity of light. The turbulent eddies that produce these scintillations have a size of the order of the aperture diameter of the LAS (or XLAS). The figure below shows that in general these fluctuations lie mostly between 1 and 10 Hz (exact positioning of the curve with respect to the x-axis is slightly dependent on the crosswind). The bandwidth of the LAS electronics is set around these fluctuations (0.1 Hz to 400 Hz). In this way electronic noise (> 400 Hz) and low frequency fluctuations related to absorption by the atmosphere (< 0.1 Hz) are removed.

Figure 1: Theoretical spectrum of a 0.15 m LAS (path length = 1 km, wind speed = 1.5 m/s).

Any type of fluctuations, e.g. caused by tower vibrations that lie within this bandwidth, in particular the ones that lie between 0.5 to 10 Hz can have significant effects on the measurements. It is therefore, strongly recommended to use stable and robust mounting platforms for the LAS units.

Yes, this is possible by logging the analog output with a fast (500 Hz) data logger, and looking at the shift in the peak of the scintillation spectrum (the scintillation power spectrum shifts linearly along the frequency domain as a function of the crosswind). In the optical microwave scintillometer , the raw data is already logged at 500Hz, so this could be implemented. Built-in data processing to calculate the crosswind may be added in the future.

See the following publication for more information: van Dinther, D., O. K. Hartogensis, and A. F. Moene, 2013: Crosswinds from a single-aperture scintillometer using spectral techniques. J. Atmos. Oceanic Technol., 30, 3–21.

The LAS MkII includes a built-in data logger, but sometimes you may wish to add the data to an existing meteorological station with its own data logger.

The LAS transmitter and receiver both have multiple analogue output signals, which can be measured by most standard data loggers. These signals allow the user to monitor the internal temperature as well as some raw signals to check the performance of the electronics. In most experiments these signals don’t have to be measured.

For general flux measurements two signals are important: the C_n² signal and Demod signal. Both signals are measured at the receiver unit. The first signal, re-scaled C_n², provides information of the turbulent intensity of the atmosphere and is used to derive the sensible heat flux (H). It’s range lies between 0 to 2.4 V for the LAS MkII (-5 and 0 Volt for the LAS150). The second signal: the demod signal is a measure of the signal strength and its range lies between 0 to 2 V for the LAS MkII (-2 and 0 Volt for the LAS150). The more positive (more negative for the LAS150), the more signal the receiver has. In general the signal strength depends on the distance between the transmitter and receiver and the opacity of the atmosphere.

The reason it is advised to measure the demod signal is that it can help with the interpretation of the C_n² signal. In some cases, the C_n² can be difficult to understand, e.g. during rainy and foggy periods, while the demod signal shows clearly whether or not the receiver has a signal, or some signal is lost due to the weather.

The LAS instrument provides the structure parameter of the refractive index of air, C_n². The latter can be considered as a parameter that describes the turbulent intensity of the atmosphere, in particularly related to the turbulent temperature fluctuations. This is way the LAS can be used to measure the sensible heat flux. However, the derivation of the sensible heat flux requires some steps. In each step additional meteorological data is required (see also processing data in the LAS manual):

Step 1: from C_n² to C_T² requires data of:

• Air temperature

• (Relative Humidity)

• Air pressure

• Bowen-ratio ( )

Step 2: from C_T² to the sensible heat flux H requires data of:

• Air temperature

• Wind speed at 1 level

Step 3: from H to evaporation requires data of:

• Net radiation

• Soil heat flux (preferably measured as closely to the soil surface as possible).

In addition, the gravitational acceleration, surface roughness and sensor heights are required.

It is recommended to have the additional data at the same measurement interval as the LAS data.

Step 4: selection of unstable or stable solution H:

For land surface, the typical diurnal course of H shows positive values during the day and negative values at night. Explanation: during (sunny) daytime conditions (roughly between sun rise and sun set) the earth’s surface heats up the atmosphere from below. This means H is pointed upward and defined positive. This situation is known as the unstable period. At night (roughly between sun set and sun rise), the surface cools due to long wave radiative cooling. As a result, heat from the atmosphere is transported downwards to the surface. Hence, H is negative. This situation is defined as the stable period. The LAS is able to measure the magnitude of the sensible heat flux (H), but not the sign, i.e. is H directed upward (> 0) or downward (< 0).

There several ways to choose either the unstable or stable solution of H:

Net radiation: During most situations when the net radiation is positive, the atmosphere is unstable. Once the net radiation becomes negative the atmosphere becomes stable. Note that this option is not applicable over intensively irrigated fields.

Global/solar radiation: Although less accurate than net radiation data, but still usable. When the global radiation is higher than approximately 20 Wm^-2, the atmosphere is unstable. When it drops below 20 Wm^-2, assume stable conditions. The exact values are site/surface dependent.

Temperature profile data: for example air temperature data collected at 0.82’ and 9.8’ height. During daytime close to the surface (0.82’), it is warmer than higher up in the atmosphere (9.8’), i.e. unstable conditions (dT/dz < 0). At night the situation is opposite, cold close to the surface and warm at higher levels, the condition is stable (dT/dz >0). This method is the most reliable one, but requires accurate temperature measurements.

C_n² data: During clear sunny days the C_n²-signal shows a very distinctive behavior. Every time the atmosphere changes transition, the C_n²-signal drops to a very small value (® 1e^-17). By determining the exact time when this occurs, the average time periods of unstable and stable conditions can be simply determined. During cloudy conditions the exact transition times are difficult to detect and is therefore difficult to automate.

The LAS manual shows a terrain classification for typical landscapes with corresponding surface roughness lengths. General meteorological literature can provide more detailed information of surface roughness length for specific surfaces and/or crops.

The surface roughness can also be determined experimentally, using e.g. eddy-covariance stations or from wind profile measurements.

This has been done, see publication by: McJannet, D. L., F. J. Cook, R. P. McGloin, H. A. McGowan, and S. Burn (2011), Estimation of evaporation and sensible heat flux from open water using a large‐aperture scintillometer, Water Resour. Res., 47, W05545, doi: 10.1029/2010WR010155.

But there are several reasons why LAS measurements of open water is rather complicated:

• In general the sensible heat flux (H) is small over lakes compared to the evaporation. As a result the derivation of C_T² from C_n² becomes sensitive to fluctuations that are produced by turbulent humidity fluctuations instead of temperature fluctuations. This correction can be expressed as a function of the Bowen-ratio. The smaller the Bowen-ratio the larger the correction. Over water bodies evaporation is (in most cases) dominant over H, resulting in small Bowen-ratio values. It is advised to have accurate Bowen-ratio data.

• Typical diurnal course of H over land shows positive values during the day and (small) negative values at night. In this way, it is relatively easy to select either the unstable or stable solution when processing fluxes (in the Evation software) as the LAS itself cannot see the sign of the flux (and thus stability). Properties of water, such as the ability to store heat (i.e. heat capacity) are very different from land. As a result it is more complicated to predict the diurnal (seasonal) cycle of H. Instead it is advised to measure the gradient of temperature over water in order to determine the sign of H.

• For the derivation of the sensible heat flux from C_T², the wind speed and surface roughness are required. As the surface roughness of open water bodies is dependent on the wave height (and thus wind speed) the standard applied flux-profile relationships cannot be used. Instead air-sea relationships have to be considered.

• To derive the evaporation from the LAS measurements (i.e. H), the soil heat flux term has to be known, i.e. the amount of heat stored in the ground or in this case stored in the water (G). For land surfaces, so-called heat flux plates can be used to measure G. For water bodies, this term is very difficult to determine.

To measure both evaporation / latent heat flux and sensible heat flux directly (and without the restrictions when using a LAS on it own), a combined optical and microwave scintillometer can be used. This system measures both C_T², C_q², and the co-variant term, C_Tq, between them, so no assumptions are made. Along with meteorological data from the receivers side mounted weather station, latent heat and sensible heat fluxes are calculated internally. See the Optical Microwave Scintillometer system page for more details.

How frequent the alignment has to be checked is dependent on the installation set-up. Tripods fixed in the ground can have the tendency to move as soil can become soft after periods of rain. In that case, the alignment has to be checked at regular intervals. Once steel constructions are used on top of buildings, or tripods on a concrete foundation, the setup is much more stable and has to be checked less frequently.

In case one has the ability to check the data in real-time, the demod signal can help to monitor the alignment. A slow decreasing trend of the demod signal can suggest possible changes in the optical alignment (ignoring degradation of the LED).

For a long term installation, stable steel constructions such as a steel frame or post, on a concrete foundation, are recommended to avoid vibration or misalignment. If tripods are used for field work, they should be fixed or tied to the ground when left unattended to avoid damage from storms knocking the tripod over. To do this, a ground anchor can be screwed into the ground under the tripod, and the tripod tied to this using a ratchet or cargo strap. Insure the tripod feet are firmly pushed into the ground first.

If there are animals in the area protect the equipment from being pushed over, disturbed, or the cables chewed, by surrounding the installation with electric fencing.

The Brewer azimuth tracker has a driving mechanism based on friction between the drive shaft and the drive plate. These items will get dirty over time and the azimuth tracker is likely to slip. This can be noticed by a tracker discrepancy after AZ or SR tests.

The drive mechanism can be cleaned by using a clean lint-free cloth with alcohol or with “garage” soap (soap with grains of sand in it). Switch the tracker power off! Remove the rear tracker cover (the cover on the side opposite to the power switch). Use the cloth with alcohol or soap to rub the dirt off the drive plate and the drive shaft. Rotate the tracker to clean the entire drive plate. Be careful not to break the wire of the safety switch. After cleaning the entire drive plate and shaft, rub them once more with a dry piece of clean lint-free cloth to remove any remaining residue of soap/alcohol.

When this is done, rotate the tracker to aim the Brewer approximately at the sun . Put the tracker cover back on and switch on the tracker power. Now the Brewer needs to perform some tracker resets. In the Brewer software, type “PD AZ SR 10” to perform these resets. Watch the data to check that the tracker resets without discrepancies and then put the Brewer software back into its normal schedule.

The Brewer instrument is capable of operating in different conditions from the tropics to the Antarctic. As the Brewer is used outside the whole year round, its Ozone measurements should not have any temperature dependency.

During the factory testing of the Brewer, it undergoes a test in the temperature chamber from 0°C to +45 °C. Standard Lamp measurements are taken throughout this entire temperature range. This is a simulated Ozone measurement based on the halogen lamp inside the Brewer. Although the intensity of the lamp does change with temperature, the wavelength shift is negligible.

After the temperature test, the data of the SL measurements is analyzed. During the analysis, the temperature correction coefficients are created. These coefficients compensate for the change in spectral response of the Brewer at the Ozone wavelengths. With the coefficients installed in the Brewer software, the Ozone measurements will not be affected by the temperature of the instrument

The Brewer software will give this error message when it tries to make a HG measurement but cannot see the light of the Mercury lamp. There are several causes why the Brewer could give this error message. One of the motors could be in an incorrect position, so that the Brewer does not see the light. The PMT could not be measuring correctly or the lamp could need replacement.

The first step in troubleshooting is doing a full reset (RE command) in the Brewer software. Then try to perform the HG test again.

If the HG test still returns the error message one should find out if this also occurs for tests with the standard lamp. Type SL<enter> in the Brewer software.

If both the HG test and the SL tests fail,, then either a motor is not moving correctly or there is a problem with the PMT/photon counting circuitry. Use the maintenance manual for further troubleshooting.

If the SL works but the HG fails, then there might be a problem with your lamp. For single board Brewers: Type AP to get the voltage of the Mercury Lamp (HG lamp). The voltage should be around 10 V. If the Voltage is off by 2 Volts, one should inspect the lamp.

The HG or mercury lamp is the lowest lamp in the lamp housing. Usually, if the lamp needs replacement, the glass will have black spots or the filament will be broken.

If the lamp needs to be replaced, do not touch the quartz envelope with your hands. Use a tissue or a piece of cloth. The lamp should be tightened firmly. Also, from the top, both filaments should be visible.

For the Brewer spectrophotometer, regular recalibration is necessary for the reliability of the Brewer’s Ozone measurements. The World Meteorological Organisation (WMO) recommends that each Brewer is calibrated at least once every two years. The Brewer is a stable instrument and drifts, however, the instruments can be monitored and corrected because of the diagnostic tests such as Standard Lamp and Dead Time measurements.

Some Brewer users prefer to have their Brewers calibrated every year. By doing this, they assure their Brewer data is of the highest quality. Drifts in the instrument are corrected sooner and the regular check with a reference Brewer increases the reliability of the data.

If you would like to discuss calibration of your Brewer at the factory or at your location please contact us.

The temperature dependence of the sensitivity is a function of the individual CHP 1. For a given instrument the response lies in the region between the curved lines. The temperature dependence of each pyrheliometer is characterized and supplied with the instrument. Each CHP 1 has built-in temperature sensors to allow corrections to be applied if required.

Typical Radiometer temperature dependence

• RaZON+ base unit, including logger

• 2 year warranty, 5 years on the sensors

• Smart Pyranometer(PR1) and Pyrheliometer (PH1) plus cables

• Power connector for 24 VDC

RaZON+ is 100% operational ready. The only thing a customer has to provide is a 24 VDC power supply.

• Only 1 pyrheliometer, the new pyrheliometer PH1 or the SHP1

• Only 1 pyranometer, the new pyranometer PR1 or any SMP

• Yes, the RaZON+ will guide you. The installation procedure can be done via Ethernet or Wi-Fi on any Smart device. You only need to mount the system on a pole or its tripod and level it. The PH1 and PR1 come pre-installed.

• On a sunny day, point the system to roughly East and start. The software takes care of fine adjustments and you can check the final position via two small holes in the pyrheliometers.

• If any azimuth adjusting is needed RaZON+ can be rotated on its tripod collar or fine adjustments can be made via WiFi and your Smart device

There is a website hosted on RaZON+ that can be accessed on any device with Ethernet and Wi-Fi that has a web browser (pc, tablet or Smart phone)

The complete set-up and local check can be done on your smartphone or tablet.

Data logging is done via the Ethernet or RS-485 port.

No, only the sensors need calibration every 2 years. Because the sensors are smart you can easily exchange them with another sensor to prevent data gaps.

• RaZON+ is a system and a data logger has been integrated. All data is placed in a database.

• All data over the last year is available.

• When power fails all data until that moment is secured

There are four ways:

• Through Modbus (pull)

• Through ASCII string (push)

• Through Ethernet (database query)

• Through WiFi (database query)

1 minute averages for 365 days

Every two years, the RaZON+ sensors need calibration. They can be sent to Kipp & Zonen for recalibration.

A firmware upgrade was implemented to accept extra Modbus sensors (pyranometer, temperature sensors) and Modbus weather stations to expand the RaZON+.

• Connect the RaZON+ with an Ethernet cable to your network

• Use a Windows PC connected to the same network

• Go to START and enter CMD in the search program window

  

• Ping the RaZON+ with its serial number (ping razon150002)

• This will show it’s IP address

• Then enter the command  “ arp  –a “

• All local IP Addresses with their (Physical) MAC Addresses are shown

• In this example  IP = 172.16.32.110

• This IP (= RaZON+) has MAC Address:  b8-27-eb-59-dc-7d 

The standard warranty of two years applies. However, you can register the PR1 pyranometer and PH1 pyrheliometer and extend the warranty on those instruments up to five years.

To register, go to www.kippzonen.com/register.

When we calibrate the sensors there is no signal bounce other than the time that the pyranometer needs to reach its final value (time constant). If, however, there are electrical inferences and the shielding of the cable and data logger is not good then you can expect noise. A good way of testing this is by connecting a dummy pyranometer with the same cable (length and position) to the data logger. (Dummy pyranometer is a 1 kOhm resistor) This will show any interference coming from the cable.

This error is related to the zero offset type A. Normally this zero offset is present when the inner dome has a different temperature from the cold junctions of the sensor. Practically this is always the case when there is a clear sky. Because of the low effective sky temperature (<0 °C), the earth surface emits roughly 100 W/m2 longwave infrared radiation upwards. The outer glass dome of a pyranometer also has this emission and cools down several degrees below air temperature (the emissivity of glass for the particular wavelength region is nearly 1). The emitted heat is attracted from the body (by conduction in the dome), from the air (by wind) and from the inner dome (through infrared radiation). The inner dome cools down too and will attract heat from the body by conduction and from the sensor by the net infrared radiation. The latter heat flow is opposite to the heat flow from absorbed solar radiation and causes the well-known zero depression at night. This negative zero offset is also present on a clear day, however, hidden in the solar radiation signal.

Zero offset type A can be checked by placing a light and IR reflecting cap over the pyranometer. The response to solar radiation will decay
with a time constant (1/e) of 1 s, but the dome temperature will go to equilibrium with a time constant of several minutes. So, after half a minute, the remaining signal represents mainly zero offset type A.

Good ventilation of domes and body is the solution to reducing zero offsets even further. Kipp & Zonen advises the CVF 3 Ventilation Unit for optimal ventilation and suppression of zero offset type A. Using the CVF 3 zero offset type A will be less than 3 W/m2

It is indeed possible to reach a value of 1400 W/m² or slightly higher. The maximum radiation from the sun above the atmosphere is 1367 W/m². However at high altitudes with a clear sky and some bright white cumulus clouds (not covering the sun) it is possible to get above the 1400 W/m². These clouds will act like a mirror and reflect (extra) solar radiation to the sensor and through this effect reach these high values. So it is possible, but only under these extreme conditions. Under a clear sky without clouds the radiation is definitely below the 1367 W/m².

Radiation incident on a flat horizontal surface originating from a point source with a defined zenith position will have an intensity value proportional to the cosine of the zenith angle of incidence. This is sometimes called the ‘cosinelaw’ or ‘cosine-response’ and is illustrated in figure 11. Ideally, a pyranometer has a directional response which is exactly the same as the cosine-law. However, in a pyranometer, the directional response is influenced by the quality, dimensions and construction of the domes. The maximum deviation from the ideal cosine-response of the pyranometer is given up to 80° angle of incidence with respect to 1000 W/m2 irradiance at normal incidence (0°).

If the Pyranometer remains horizontal, the error involved is the directional error listed in the Pyranometer brochure.

For CMP 3 < 20 W/m²  and for CMP 22 < 5 W/m²

The CMP series can also be used under water, the depth is limited to 3’ and can only be used for short measurements.

It is advisable not to keep the Pyranometer of the CMP series under water for longer than 30 minutes.

The SP Lite2 pyranometer and the PQS 1 PAR Quantum Sensor can be used for a longer period under water, the depth is limited to 6.5 feet. Please also take “breaking of light on the water surface” in consideration.

Yes, however the data logger needs to be placed on the surface (it is weather resistant, but cannot be lowered into the water).

We advise to re-calibrate the Pyranometer every two years.

The 50 % points are the wavelengths where the output of the instrument is 50 % reduced with 100 % input.

The instrument has an analog output, therefore the resolution is infinite. Every change is noticed, no matter how small it is.

The bandwidth of most pyranometers is 285 to 2800 nm. This covers the full solar spectrum as shown below.

• CMP22 has a bandwidth of 200-3600nm (Quartz glass )

• SP Lite  has a bandwidth of 400-1100nm (silicon photo diode)

• CMP3 has a bandwidth of 300-2800nm

The disturbance on the cables on the CMP 11 is difficult to judge from a distance. A test would give the best criteria in this case.

Simply cover the CMP 11 so it is fully dark (in box with cloth etc.) Log the data over a period that disturbance is expected, at least one day.

If the data is zero, no problems are expected.

• No, we do not have filters for any of our pyranometers. The only way to do this in a correct way is to use a filter dome. Otherwise the directional response would be affected.

The AMPBOX is the best solution.

You will need a suitable PSU and a shunt resistor of 500 Ω to convert the current output (4..20mA) to a voltage output of 2-10V , or you will need a shunt resistor of 50 Ω to convert the current to a voltage output of 0.2-1V.

CMP 6 in combination with PQS1 PAR Quantum Sensor is advised. CMP 6 for outside usage to measure global solar radiation. PQS1 to measure PAR radiation inside which is most sensitive for plants and crops.

For this application, the CMP10 and SMP10 are advised as they have an internal drying cartridge that will last for at least ten years.

Please note that the pyranometer needs to be mounted in the same angle (POA) as the PV panel.

For users that prefer the desiccant to be visible, Kipp & Zonen offers the CMP11 and SMP11 with visible and user changeable desiccant.

None. Solar concentrators are reflecting the direct solar radiation to a concentrator and are tracking the sun. You will need a pyrheliometer on a sun tracker to measure direct solar radiation.

Yes, we do have a Pyranometer with the same spectral characteristics as a PV panel. This is the SP Lite(2) Pyranometer.

Our SP-Lite is based on a silicon diode which has a response from 400 – 1100 nm.
The advantage is the response time, which is as fast as any PV panel ( milli seconds).
The disadvantage is that not all PV panels have the same spectral range. 
A thermopile pyranometer covers the full spectral range of the sun and will give a more accurate measurement of the total (global) solar radiation.

The output from thermopile Pyranometers, such as our CMP Series, is very low – typically around 10 milli-volts on a clear sunny day. To resolve changes of 1 W/m² requires an ADC with an accuracy and resolution of around 5 micro-volts. These PC interfaces are very expensive and difficult to find in a form that is easily interfaced to the PC. This is why meteorological data loggers are normally used that can cope with the low signal levels.

Kipp & Zonen has solutions like handheld- or fixed location data loggers.

The CMP 6, as with all our solar radiometers based on thermopiles has a continuous small analog voltage output. For CMP 6 an irradiance of 1 W/^m2 generates an output signal in the region of 5 to 15 micro-volts. We have additional solutions to increase this voltage.

NIST in the USA supplies calibration services to industry – in case of light they characterise sensors, detectors and lamps for use in manufacturing and for luminance measurement (LUX).

They are not set up for the calibration of sensors for solar radiation and they are not a traceable reference. 

The only accepted world standards for the calibration of radiometers for the measurement of global or direct broadband solar radiation are as below:

• ISO 9059 Calibration of Field Pyrheliometers by Comparison to a Reference Pyrheliometer

• ISO 9060 Specification and Classification of Instruments for Measuring Hemispherical Solar and Direct Solar Radiation

• ISO 9846 Calibration of a Pyranometer Using a Pyrheliometer Guide to Meteorological Instruments and Methods of Observation, Fifth ed., WMO-No. 8

By physical laws, any object having a certain temperature will exchange radiation with its surroundings. The domes of upward facing radiometers will exchange radiation primarily with the relatively cold atmosphere. In general, the atmosphere will be cooler than the ambient temperature at the Earth’s surface. For example, a clear sky can have an effective temperature up to 50°C cooler, whereas an overcast sky will have roughly the same temperature as the Earth’s surface. Due to this, the Pyranometer dome will ‘lose’ energy to the colder atmosphere. This causes the dome to become cooler than the rest of the instrument. This temperature difference between the detector and the instrument housing will generate a small negative output signal which is commonly called Zero Offset type A. This effect is minimized by using an inner dome. This inner dome acts as a ‘radiation buffer’.

The Zero Offset A can also be reduced by using a Ventilation Unit CVF 3.

No, all the Pyranometers have a 180 degree field of view. When mounted horizontally, they cannot see light reflected from the ground due to its design.

The CMP 11 uses a default temperature compensation setting and the dependency is ±1% from -10 to +40°C.

The CMP 21 is individually tested, and the temperature compensation is optimized. It is ±1% from -20 to +50°C. However, from -10 to +40°C it is within ± 0.5%, typically ± 0.3%. In addition, a temperature sensor is fitted, and the temperature response curve is supplied. Each CMP 21 has the directional (cosine) response tested, and this is also supplied. This means that for the serious scientist the irradiance values can be corrected for temperature and solar elevation – increasing the accuracy. This is not possible with the CMP 11.

BSRN requirements state that the solar radiometers must be fitted with an internal temperature sensor and the data recorded, so CMP 21 is compliant to this, but CMP 11 is not. 

Our thermopile-based instruments, including the CMP range of pyranometers and the CH(P) 1 pyrheliometer, do not require power to operate. They generate a small voltage output in response to the solar radiation.

Yes. Normally 4 of these side-mounted sensors is the maximum, however we are able to make an extension on one pyrheliometer mount for the extra sun-sensor.

The power use of the 2AP itself is about 1.5 A to 2 Amps. (internal fuse is 3 Amps slow)

The power use of the 2AP itself is about 1.5 A to 2 Amps. (Internal fuse is 3 Amps slow)

Part number for the 24V heater kit is: 12136346.
This kit contains two 50 Watt heaters.
So the current for these heaters is 4.2 A (at 24V), fuse is 5 A slow blow.

If we add up the total power we have:
5A (heaters) + 3.15 (2AP)= 8.15 A

Normal conditions:
4.2 A (heaters) + 1.25A (2AP) = 5.5 A normal

Therefore a 5 Amp power supply will not survive very long.
We recommend to take a power supply that can deliver the 8.15 A. (when heaters are used)

The 2AP works fully autonomously, after the setup. Setup is done in combination with a PC. (Entering Longitude, Latitude etc.) Indeed a data logger is needed to collect data from the sensors, but this logger has no (hardware) connection with the 2AP.

To connect the 2AP with a PC for communication, a 3-wire cable is used (or 2 wires plus shield) as described on page 5 of the manual.
Advised is a shielded cable, where the shield can be the ground connection.

• On the 2AP side the wires are connected to the communication board.

• On the PC side a 9 or 25 pin Sub D connector is used for the serial port.

This cable length can be 98 feet. 

The communication software is included with the 2AP

The CMD and sun tracker software will work on COM1 or COM2 only, specified as the first parameter after the program name in the command line. Make sure the 2AP is connected to one of these two ports. Problems can also occur if another program has taken over the COM port and will not give it up. Also, some Compaq computers have non-standard COM ports, which the CMD and sun tracker programs cannot communicate through. The solution for this problem could be found in a simple add-on card with a standard extra serial port, if it can be set as COM 1 or 2

The temperature range for the 2AP tracker is:

Standard temp range: 0 - 50 degrees Celsius
With cold cover: -20 - 50 degrees Celsius
With cold cover and heater -50 - 50 Degrees Celsius

Normally the heater is built in, in the factory. However we can supply you with a kit plus instructions to do it yourself.

The 2AP has the following errors:

• Time

• Setup (leveling)

• Calculation (algorithm according to Michailsky error max. is 0.025 degree)

• Mechanical (BD = 0.09 and GD =0.045 degree max.)

The first two are user controlled and the last two are fixed.

Assuming that the leveling is optimal, the only error remaining that can be corrected is time. If we assume that the clock is reset every 1,000,000 seconds (11.5 days) there will be an expected error of five seconds. If we assume that the sun rotates 360 degrees in 24 hour then RMS 0.72 * 5 seconds = an actual time error of 3.6 seconds. For a period of 11.5 days the total time error contribution is 0.015 degrees (the diameter of the solar disk is 0.25 degrees). Per year, this would result in 0.5 degree.

If this time correction and the check on leveling are done in regular intervals, there is no need for a sun sensor. If, however, this interval can or will not be made, the sun sensor will correct for both (leveling and time).

The sun sensor is normally used for first checking the tilt error, assuming that there is sunshine for at least two full days over the full day. This information is stored in an internal log file and used to correct (in combination with PC). Over this period the user has to correct time (if more than 2 weeks). After this initial run and correction for tilt, the sun sensor is used for time correction. This means that optimal accuracy is maintained without user (time) correction. This means that the 2AP is within specs the whole year without intervention.

Please note that the sensors used on the 2AP also need maintenance on a regular basis (drying cartridge and dirt on domes).

The 2AP error in degrees can be calculated as percentage of 360 degrees, but the error in sensor reading depends on the type of sensor.

The controller board has a temperature compensated oscillator module for the microprocessor. While power is applied, the firmware keeps accurate time and updates the real time clock (which is not very accurate) every 8 hours.

We enter a room temperature correction, which compensates for initial calibration of the oscillator module. The oscillator module can drift up to ±11 ppm over the 0 °C to 70 °C temperature range. The module can also drift up to ±2 ppm in a year.

The temperature drift is different for each oscillator, so it cannot be compensated for in firmware.

The air pressure that is required should be an average value for the site the instrument is operated. It does not need to be updated over time. The meaning of it is to correct for (a small) optical shift due to atmospheric pressure. A normal value depends of course on the health of the operation. A value of 1000 mBar is typical for sea level.

You can try the following:
If you send the command “CO”, the 2AP will cold start. This means, ignore all present settings and start without using any previous (possibly wrong) settings.

If you then start the sun tracker program, it will start up with the message “”recovering from cold start””.

Then longitude and latitude etc. will be recovered from the .ini file, the time and date of course cannot be stored and has to be entered again. If no further error message is given, the 2AP is most likely operational again.

This could solve the problem, if not please contact us and we will discuss further options.

The 2AP BD altitude specification (2000m (6,500')) is limited by the CE and CSA (Canadian Standards Association) recommendation for the main power board design. CSA recommends that AC boards have certain spacings between the board tracings for various elevation (pressures). As the pressure decreases, there is more probability for arcing when the wires are close. Unfortunately, there is not enough room internally, in the 2AP BD, to increase the size of this board (to make the spacings bigger).

The best solution is to sell/quote a 2AP Gear Drive with 24 VDC, as this would eliminate the altitude restrictions associated with high voltage AC.

Standard one CHP 1 mount is included. An extra mounting clamp can be added on top of this CHP 1 mounting. The same can be done on the other side. So standard, four CHP 1’s is possible.

The SOLYS Gear Drive can easily handle more, but for mounting for more instruments (e.g. 8 pyrheliometers), a larger mounting plate is required.

Pointing accuracy is better than 0.02°, when active tracking, under all conditions.

Yes, like on the SOLYS 2 a special mounting clamp is available for the PMO-6.

The power supplies used in the SOLYS have EN60950-1 approvals. This means it is approved up to 16,404 feet. If higher altitudes are required, we can check or test if this is feasible.

It takes a few minutes for the SOLYS to return to its home position. Then the SOLYS goes to sleep mode (for power reduction).

Yes, both the Solar Zenith and Azimuth positions and the SOLYS motor Zenith and Azimuth positions are available in the log file.

The power requirement is for both AC and DC is 25 Watt during operation and 13 Watt at night. For the SOLYS, “night” is from ~ 5 minutes after sunset to ~ 5 minutes before sunrise.

When used in cold climates, the heater switches on to keep the interior above -20°C.

This is switched automatically and only used when powered from AC.

The cold cover can be used to reduce the required heating power.

The Sun Sensor is supplied as standard with the SOLYS Gear Drive. If it is removed (or not mounted), then the SOLYS will follow the sun based on its internal calculation.

This is normally accurate enough but but does not correct for any misalignment or unstable mounting.

Like our radiometers, the SOLYS’s are made of anodized aluminum. Until now, we have not seen any effect on the functioning of the trackers that are mounted on the seashore.

The SOLYS also has a paint coating to further protect it.

Absolutely! Great care has been put in to extending the temperature range and minimizing the possible disturbance from dry air (ESD) to make the SOLYS Gear Drive suitable for this climate.

Filters can be ordered in sets of 5.

The AMPBOX can be delivered in two versions:

• standard, then the gain is 1 mV = 1 mA

• adjusted, then the gain is set to 0 – 1600 W/m² = 4 – 20 mA

The AMPBOX has a 20 bits A/D on the input and a 16 bits A/D on the output.

The maximum error from the AMPBOX is ±0.05% of span or ±10 µV (over the full temp range)

This means in daily use that the additional error of the AMPBOX is far below 1 W/m² for all radiometers.

The gain range is the ability to adjust the amplification to the sensitivity of the radiometer:

• Gain adjust --> 0.1 to 4 mA/mV

• Input voltage range --> -12 to 50 mV

As mentioned above, the amplification can be adjusted to 0- 1600 W/m² = 4 – 20 mA.

In this case, 100 W/m² change on the input gives 1 mA change on the output.

The benefit is that two different sensors with different sensitivities have an identical output from the AMPBOX.

The zero adjust is used for the pyrgeometer to allow negative inputs.
The pyrgeometers are adjusted for -300 to +100 W/m² = 4 to 20 mA.
So 100 W/m² change on the input gives 4 mA change on the output. The zero point for the pyrgeometer is set to 16 mA. This is because a pyrgeometer can be more negative than positive.

To keep the outer dome at the same temperature as the surrounding air temperature. This will keep the zero (a) offset as low as possible. But also to keep the dome as dry and clean as possible (from rain snow, ice and dirt).

It is advised to use 5 Watt heater to keep the offset (a) as low as possible. This can be used during the whole day. If the surrounding temperature is above zero, this should be sufficient. Below zero degree Celsius, the extra 5 Watt (10 Watt total) can be used. We recommend using the 10 Watt heater only during the morning (few hours around (preferable before) sunrise) to get the dome clean when measurement starts. After that, the heater can be set back to 5 Watt.

Yes you can, by using a shunt resistor and a suitable power supply unit (PSU). You will need a shunt resistor of 500 Ω to convert the output current (4..20mA) to a voltage output of 2-10V.  Or you will need a shunt resistor of 50 Ω to convert the current to a voltage output of 0.2-1V.

The AMPBOX is set for 0 - 1600 W/m²  for 4 – 20 mA
For CMP 3 with 16.51 μV sensitivity, this is 0 - 16.51 * 1600 μV =0 - 26.416 mV for 4 - 20mA  (delta = 16 mA)
Sensitivity AMPBOX = 26.416 mV per 16 mA  =  1.651 mV per 1 mA or 1651 μV per 1 mA

Now connected PAR with 5.59 μV/μmol.     1651 / 5.59 = 295.35 μmol per mA

Therefore:
0 μmol = 4 mA 
295.35 μmol = 5 mA etc.
4725.6 μmol = 20mA as maximum input

No, 0,1μmol/m²s input will result in a very small change on the output of the AMPBOX (around 4,00033 mA). This is outside the accuracy of the AMPBOX and the accuracy of the PAR Lite.

No, the METEON will not work together with an AMPBOX.

With a 10 Ohm resistor the 20 mA output from the AMPBOX can be converted to 0.2 V max signal (max for the METEON). But the METEON cannot deal with the zero offset from the AMPBOX (4 mA).

If the AMPBOX is purchased together with a new pyranometer, or for use with an existing pyranometer, it has the sensitivity of that pyranometer programmed internally.  In this case, 0-1600 W/m2 of irradiance on the pyranometer produces 4-20mA from the AMPBOX. The serial number of the pyranometer matching the AMPBOX should be present on a label on the AMPBOX.

No, it cannot separate UV-A from UV-B, it measures both together, for measurement of these parameters individually we recommend our UVS Series of radiometers.

We advise to re-calibrate the UV radiometers every two years.

No, the input range of the METEON is limited to 200 mV (the output from the UVS-X goes up to 3V)

The ‘Mean Adjustment Factor’ on the calibration certificate is equivalent to the sensitivity of a pyranometer. It applies to specific Ozone column and Air-mass (solar elevation) values used as the standard test conditions. Data files are provided to correct the measured values for other Ozone and Air-mass conditions (see Radiation Amplification Factor).

No, we do not have a UV-C sensor. UV-C from the sun is almost completely absorbed by Ozone in the atmosphere and virtually none reaches the ground. 

Our thermostat is better than a temperature compensation. We used to have UVS-X-C versions of our instrument (these were temperature compensated). We stopped that line because the UVS-X-T version performed much better. Temperature compensation means correcting the output for changes in sensor temperature. Because our sensor is always the same temperature, there is no compensation required. The internal Peltier element heats or cools the actual complete detection system that measures the UV light.

The bandwidth of the CUV 4 is 280 - 400nm. The 50 % points are defined to be 290 - 385 nm.

The radiation amplification factor is a correction for solar zenith angle and Ozone column. This is required because these two factors strongly influence the UV measurement.

The UVIATOR can work with any data logger that is capable of storing UVS measurements. The UV-data must be stored in the correct format. More details can be found in the UVIATOR manual.

For easy correction for solar zenith angle and Ozone column.

This is required because these two factors strongly influence the UV measurement. With the UVIATOR software, you can collect the Ozone column data from the OMI satellite data per date, time and location. With this Ozone data and the solar zenith angle, the UVIATOR will calculate the optimal correction for every data point.

The UVS series of UV radiometers have an output in the range from 0 - 3 V.

No. According to the WMO / WHO guidelines for the Global UV Index, UV-I should only be derived from UV-E measurements (or from a spectral instrument such as our Brewer Spectrophotometer).

Yes, the UVS-AB has two independent detection systems.

The UVS-AB has two continuous, simultaneous, analog outputs; one for UV-A and one for UV-B.
See the below drawing of the UVS-AB for details.

Beneath the dome and diffuser two sets of filters and detectors are positioned. Detector 1 is 4 times bigger than detector 2. Detector 2 is located exactly in the middle, on top of detector 1. Filter 1 has an opening in the middle for filter 2 plus detector 2. In this way, we can make sure both detectors have a 180-degree field of view.

Sometimes it happens that the colors of the cables are different when you order extended cables. Usually, there is an added page in the manual where this is mentioned.

Standard = extended
White = white
Green = blue
Black = black

The correction factor in the manual could indeed be written more carefully. It says dividing by (1+x.V^3/4) this refers to the calibration factor. Better is to say the output should be multiplied with a factor (1+x.V^3/4).

There is no general value to use but some criteria to keep in mind to select a Pt-100 current.

Because the Pt-100 (unlike a thermocouple) needs current, it is advised to keep this current as low as possible to avoid self-heating of the Pt-100 by its own current. The Pt-100 measuring device (like our data loggers CC 48, CR10X) has a fixed current, in such a way that the voltage over the Pt-100 is matched with the Pt-100 (voltage) measuring input of these loggers.

In general, the current for a Pt-100 is indeed between 0.1 and 1 mA. This would result (@ 0ºC) in a voltage over the Pt-100 of 10 mV or 100 mV. Therefore, the current can also be selected depending on the available input range of the measuring device. The error introduced by self-heating, when using a 1 mA current, is quite low (< 0.2ºC) because the Pt-100 is very well connected to the body of the CNR1. When the heater of the CNR1 is on, the error introduced by the heater in measuring the body temperature is typical 2º C (see manual).

The benefit of a larger current (1 mA) is that electrical disturbances have less effect when the current is larger.

To summarize these facts I would say, 1 mA measuring current is accurate enough, but the output voltage in this case (0.1 Volt) has to match the measuring input range.

Response time for CNR1 sensors: 5 s (63%) en 18 s (95%)

Both instruments use thermopiles, but the dome over the thermopile determines what kind of radiation passes through and reaches the thermopile. A thermopile is normally protected by a single or double dome to reduce offsets caused by sudden temperature changes like wind.

The CNR 2 uses two glass domes to cover the pyranometer and two silicon domes to cover the pyrgeometers. It uses TWO thermopile detectors (1 for each of the two pyranometers and 1 for each of the two pyrgeometers) and provides two separate outputs. One NETTO for short wave (solar spectrum) and one NETTO for long wave radiation. (Far Infrared spectrum).

So yes, the CNR 2 has separate thermopiles to measure Far Infrared and Solar radiation and so do the other CNR net radiometers.

The detector from the NR Lite(2) is not protected and is in direct contact with the weather conditions. Therefore, it cools down a lot faster by the wind, which effects the accuracy of the measurements. The NR Lite(2) uses NO dome. It uses only TWO detectors with a PTFE coating and provides ONE single output for NETTO short wave- and long wave radiation.  It uses one thermopile to measure the full spectrum of Far Infrared and solar radiation.

The difference between the NR Lite(2) and CNR 2 lies in the material used to cover the thermopiles.

CNR 2 uses glass domes for the pyranometers (that measure short wave radiation) that have a bandwidth of 300 nm to 2800 nm. It uses silicon domes for the pyrgeometers (that measure long wave radiation) that have a bandwidth of 4500 nm to 42000 nm. This leaves a gap between 2800 nm and 4500 nm. This is the so called atmospheric window where very little radiation comes in (see picture below).

The NR Lite(2) uses NO domes. It uses two detectors with a PTFE coating which have a bandwidth of 200 nm to 100.000 nm.

We do not have charts or tables indicating irrigation requirements for various plots of land (i.e. based on differing vegetation and climatic factors). There are many scientific publications that refer to evaporation rates from crops, but none, to our knowledge, that specifically link PAR readings from our sensor to irrigation.

There is something as a "reference crop evaporation" or "actual evaporation" that can be derived from net radiation (solar plus thermal) together with surface temperature, soil and vegetation data. Unfortunately, we do not have the information to do it today. However, there is a simpler approach in which the expected evaporation is coupled to the total dose of global radiation as measured by a horizontal pyranometer.

If NOAA or a Meteorological entity gives such figures for your area, it is important to know the relation between PAR intensity and total global irradiance for at least a solar spectrum at air mass 1.5 (solar elevation 53°).

This relation is for:
Clear sky: 681 W/m² total, 308 W/m² in the 400 to700 nm band 1408 µmol/s.m² PAR
Light cloud cover: 200 W/m² total, 109 W/m² in the 400 to 700 nm band 493 µmol/s.m² PAR

Be aware that many green leaves are highly reflective for near IR but absorb strongly in the 400 to 700 nm band (PAR region). For evaporation only W/m² counts and for photosynthesis only photons counts.

Yes, however the depth is limited to 6.5 feet. Please also take the “breaking of light on the water surface” into consideration. This affects the calibration factor.

We advise to re-calibrate the PQS 1 (PAR Lite) radiometer every two years.

0,001 µmol represents a voltage of 5nV (nano Volt). As you can understand this very low voltage cannot be measured with a data logger. Besides the absolute error from the data logger, the PQS 1 PAR quantum sensor (PAR Lite) also has some specifications to consider.
There is the non-stability, non-linear, temperature dependence and the quantum response. Measurements under 1 µmol/m²s are not to be trusted as accurate. (effective limit)

The extension is .TXT or .XLS. Using the software interface you can select to save this as a text or Excel file.

The format uses columns,  for example:

The LOGBOX SD has one input for power. You either connect the internal battery or an external power source. So external power will not switch off the battery.

PWR OUT will provide whatever power is connected as power source for the LOGBOX SD.

No, the METEON will not work together with the AMPBOX. With a 10 Ohm resistor the 20 mA output from the AMPBOX can be converted to 0.2 V max signal (max for the METEON). But the METEON cannot deal with the zero offset of the AMPBOX (4 mA).

The logging interval can be selected from 2 to 65.535 seconds.

With two AA size internal Alkaline batteries.

The METEON is not suitable for unprotected outdoor use. However, the operating temperature range is – 10 ºC to + 40 ºC. When it is placed in an enclosure protected from dust and rain, it would be possible in practice.

The SOLRAD can be used as a very cost-effective and well performing real-time interface to a PC serial port, logging the data on the PC with the supplied software.

The METEON however, cannot do this. You need to download the data periodically using the supplied software. The METEON interface is USB.

Please check the calibration factor of the pyranometer which is set in the METEON. A wrong calibration factor of the instrument will result in wrong measurements. Also check if the correct instrument is selected.

Adding the intervals without dividing this by the (interval) time.

For example:
 
Radiation in the morning 4 hours 400 W/m².
Radiation in the afternoon 4 hours 600 W/m².
 
If you would take a 60 minute interval on the same day:
Morning = 4 intervals of 400 W/m²
Afternoon = 4 intervals of 600 W/m²
Total over the day 4 x 400 + 4 x 600 = 1600 + 2400 = 4000 W/m² (over hourly interval)
This is 4000 W/m² per hour or 4000 Wh

The stored interval in METEON is 30 minutes.
During the morning you will get 8 intervals of 400 W/m²
During the afternoon you will get 8 intervals of 600 W/m²
16 intervals (of 30 minutes) with a total of 8 x 400 + 8 x 600 = 8000 W/m² (over 30 min interval)
This is 8000/2 = 4000 W/m² per hour or 4000 Wh

Yes, the SOLRAD is perfect because it has a 0-10V input range available (the output of the UVS meter is 0-3V).

Please consider that the SOLRAD is intended to display real-time values and/or to store the integrated values for a day. If you fully want to use data logger options, it is better to use a LOGBOX SD.

The UVS has a ‘Mean Adjustment Factor’ on the calibration certificate.  This is equivalent to the sensitivity of a Pyranometer.  This can be entered into the SOLRAD and the readings will be in W/m².

The SOLRAD is not a data logger. It is intended to display real-time values and/or to store the integrated values for a day. 31 records allows a month of daily integrated values to be stored. 

The internal battery will only run it for a little more than one day. For longer periods it requires an external DC supply.

It is not suitable for unprotected outdoor use. However, if it is in an enclosure protected from dust and rain it would be OK in practice.

The DustIQ measures the amount of light relected by the dust back into the sensor. This is converted into Transmission Loss and Soiling Ratio. The DustIQ reports 2 independent transmission losses and soiling ratios of its 2 sensors. (Transmission loss = 100% - soiling ratio)

Transmission loss, according to several publications and reports, directly translates into energy loss because the relationship is almost linear for soiling losses up to 20%.

Transmission Loss measurement Accuracy: ± 10% of reading after local dust calibration (not including zero offset). Zero offset: less than ± 1% when clean.

The zero offset can be subtracted from the measurements to reach zero again. E.g. a Transmission Loss of 0.3% for a completely clean DustIQ is within specification and can be compensated by TL_corrected = TL - 0.3 or Soiling Ratio_corrected = Soiling Ratio + 0.3

When installed next to or in between the actual PV modules the relationship is between 80 and 100%.

A 2-panel system with PV modules identical to the ones used in the PV plant and cleaned every day is the most accurate but also most expensive solution. It is also very unlikely that a 2-panel system can be installed right in between the real PV modules and thus the soiling will be different. The DustIQ is the optimum balance between accuracy and being maintenance-free with a low TCO.

The DustIQ can measure up to 50% soiling loss.

The DustIQ is installed next to or in between the actual PV modules and will get the same dust, wind, rain and cleaning. The surface is also very similar to a many PV modules.

The silicon cell is only used once for the local dust calibration to correlate the step change in energy with the optical sensor measurement.

The DustIQ uses its own Optical Soiling Measurement. The DustIQ performance is not affected by external factors in the temperature range given in the specifications: from -20 to +60° C.

The PV module temperature sensor (now always present) can be connected to the second port on the DustIQ to measure the rear temperature of a nearby PV module. The IEC advises to take many temperature measurements to be able to take the PV module temperature into account in the Performance Ratio calculations.

The standard IEC61724-01 on monitoring gives recommendations. Due to copyright we cannot share the document. Table 1 in the document advises as follows:

5MW 1 instrument
40MW 2 instruments
100MW 3 instruments
200MW 4 instruments
300MW 5 instruments
500MW 6 instruments
Please see here for a preview and ways to buy the document.

IEC 61724 specifies two methods to measure soiling:
Method 1: max power and temperature of the soiled device
Method 2: short-circuit current and temperature measurement
The DustIQ output is equivalent to the short-circuit current method. Obviously it does not measure short-circuit current but the reflected light, that then is translated into transmission loss. The local dust calibration is done based on the step change of the short-circuit current of the built-in silicon panel.

Yes, it is. Although the Thin-film might react a little bit different, the relationship between sunlight lost due to soiling and energy loss remains the same.

This question is best answered by the people supplying the dry cleaning robots. However, we have seen dry cleaning robots to reach 0.5% soiling loss compared to 8% loss before the cleaning. Wet cleaning sometimes is better but only when done very carefully, with very clean water and in absence of wind that brings new dust directly sticking to the wet PV modules.

The short answer is no. The data produced needs "clever" robot control software to filter out rain and dew events, to be able to start a cleaning cycle. Humans can see immediately from a graph and the weather report what happened. Computers need machine learning and AI. Thus, in the future this can be possible.

The DustIQ doesn't have Wi-Fi as customers told us they don't trust the connection to be 100% available all the time. Therefore, we use Modbus RTU over RS-485 wired connection that also supplies the 12-24V power. However, the solution can be made wireless by using an integrator or customer supplied RS-485 to Wi-Fi converter and Modbus over TCP/IP.

Absolutely. The DustIQ produces Modbus registers to be read. Please see the manual.

Yes. The DustIQ is made with glass and aluminium with PV standard quality. Thus the same procedures for using and cleaning the PV modules can be used.

There is no direct relationship between the soiling of the flat DustIQ and the round glass dome of a pyranometer. Also the influence of soiling on a round dome on solar radiation measurement changes from plus to minus over the day and with the angle of the sun. Currently, there is no better solution than regular cleaning of the dome.

Only blue LEDs are available with manufacturer documents to show long time stability in UV rich environments.

Analyses show that the bottom of PV modules often gets soiled more than the top part and so will the bottom DustIQ sensor. Resulting in higher reported transmission loss

According to IEC 61724-01, soiling monitoring is necessary when energy losses can exceed more than 2%. In areas with a lot of rainfall, this probability is very small and measuring soiling would not be needed.

The DustIQ takes a measurement once per minute. It operates throughout the whole day. The measurements are reliable as long as the device is dry. Storing 24x7 measurements of every minute does not really make sense as soiling grows very slowly. A few measurement points per day are enough.

Its length (996 mm) is the most common width of PV modules as is its height (35mm). The aluminium frame and glass are PV module equivalent, too.

No, it cannot. Thanks to its measurement principle, DustIQ does not need that to improve accuracy. Unlike 2-panel systems that rely on the sunlight.

Theoretically, the DustIQ measurement could be different then. According to the experience our customers made, the results are still close enough.

Bird droppings are very local and only a 2-panel system can work accurately. However, preventing bird colonies even when building the PV plant is paramount. Cleaning is very difficult or expensive and once colonized, the birds are difficult to deter.

Normal 2-panel systems require daily cleaning of the clean reference cell or panel, they do not fit in between the real PV modules and they only work well on sunny, cloudless days around solar noon. The DustIQ works 24/7 as long as the DustIQ is free from rain or dew. It even works up-side-down for bifacial PV plants.

They both use optical soiling measurement. The MARS uses a camera and only works around sunset and with a clear sky. Thus, one measurement window per day. The DustIQ measures accurately 24x7 as long as the DustIQ itself is dry. Supposedly, the MARS does not need dust calibration, but no proof has been published.

It works for all silicon- based PV modules and also upside down for bifacial.

The DustIQ has not been designed for that.

This is under investigation.

The DustIQ is installed next to or in between the actual PV modules.

For long term installation the DustIQ needs mounting support. Either from two adjacent PV modules or its own support structure.

Yes, that is possible.

Only once. The calibration is valid for the whole lifetime of the device.

It is needed only once to make sure the effect of your local dust is used to get the best measurements.

The DustIQ does not need recalibration for at least 5-10 years as it has extra internal sensors and compensation for any potential wear or drift.

No. All components have been selected in such a way that we do not anticipate factory recalibration. A local dust calibration also measures and corrects for any future deviation from the original factory calibration.

The DustIQ works with dust it has been calibrated with. For the factory calibration it is Arizona Test Dust. For other dust types, the DustIQ can be calibrated locally, it cannot be calculated or "programmed".

The data will be less accurate most likely. After local dust calibration the "old" data can be post-processed as described in the manual.

Ideally, perform a local dust calibration soon after and record the mentioned Modbus registers for dust slopes before and after. Going back to factory settings is possible.

We have compiled all relevant information on a separate page. Please see this page. 

The DustIQ is never cleaned on its own. It is only cleaned when the actual PV modules are cleaned. Then it remains "in sync" with the real PV modules.

The DustIQ is made of PV module material like the glass and aluminium. Thus, the same procedures as for cleaning the PV modules can be used.

Remove all data when the weather station indicates rain (30 minutes before and 1 hr after) and when the dew point is close to or below the PV module temperature (dew). Or install a Modbus dew-rain sensor next to the DustIQ.

Probably not, but the PV plant owner might ask you to show that indeed the PV modules were cleaned (step change in soiling loss) and how good the robots do their job (how close to 0% loss you get).

After a reset ( switching On/Off the sensor), every WS-Sensor will start up for the first five seconds in UMB-protocol and the standard baud rate of 19200Bd, independent to the configured protocol and baud rate settings of the WS-Sensor.

In the first five seconds, you will be able to connect via UMB-config-Tool to the WS-Sensor. After the first command is sent, the UMB-protocol will stay for ten minutes before it switches back to the original configured protocol. This time will always be extended to ten minutes if a new UMB command was sent.

The WS800 uses an integrated electronic chip to detect lightning.The max. radius of this detection is approximately six miles.

The wiring plan has changed compared to the wiring plan of older WS-Sensor device versions.

The new wiring plan is:

• +VDD = brown
• GND = white
• SDI12_Signal = yellow
• SDI12_GND = white

This is also mentioned as a note in the latest WS-sensor manual in the section 8 Connections.

The 24 GHz Microwave Doppler Radar works with the radar reflection method and measures the precipitation quantity or precipitation intensity by means of the correlation of drop size and velocity below the sensor.

Inside the smart sensor, a drop size distribution matrix enables to calculate intensity of precipitation and to determine type of precipitation according to fundamental meteorological relationships (Gunn-Kinzer and Hobbs and Locatelli).

More to read about the measurement principle in the WS100 Sensor Guide.

The measuring spot of the mobile sensor is approx. 10cm x 10cm in the specified distance. This applies to both the 1m and the 2m version.

If the distance deviates from this, the measuring spot becomes correspondingly larger (with larger distance) or smaller (with smaller distance).

However, it should also be noted that the area of the transmitter and the receiver move further and further apart, as the MARWIS "squints" a little.

Laser Diode Module (LDM) is the most critical part Expected life time:

• >45,000 h (limited to laser diode MTBF; 4-5 years; runs normal between 100 000 to 200 000 hours)
• MTBF: 45,000 h

You can fix a heater mat on the metal tube, e.g. with 10W power. This would also be the best way to defrost the window of the sensor. Hot water on a frozen window can lead to a serious damage and should be avoided.

A special tube may be added.

• Front: 70mm

• Middle: 100 mm

• End: 50mm (connection to the sensor)

An extra Lufft accessory is planned for the future

The SHM31 is mainly designed to measure the snow depth. The measuring principle is not applicable to measure pure ice or water due to strong reflections or translucency. For ice and water on roads, please view our road sensors like NIRS31, MARWIS/StaRWIS and ARS/IRS31Pro.

The sensor can operate until -10°C outer temperature without a heater. Turning the heater off above -10°C would not affect the measurement, but the outer window might get opaque due to condensation/ freezing over time.

The power consumption at 12 VDC is roughly: 2.5 W if only the window heater is enabled and 18 W with window and main heater switched on.

The heaters can be activated/deactivated also with SDI-12. Additionally, the heaters could be deactivated with a voltage level at the red 3-pin (configurable).

There are no limitations. But the current will be a bit higher to get the same heating power as with 24V.

Yes it can be switched off for a longer time. There is a defrost mode that can be activated by default, if the sensor is switched on in very cold environments. It can take 2 minutes or 10-15 minutes to wake up the sensor, depending whether the outer conditions are very cold (-40°C ) or moderate (-10°C).

A simulator generates different light pulses and background light levels to test the detection unit and the data acquisition path of our CHM units. The starting point is the laser itself. The laser pulse is detected by the simulator and time shifted LED pulses are generated. By comparison with the instrument specific production protocol, the user can easily see differences in the calibration. The simulator takes a test time of 30 minutes in maximum and should be repeated once per year to verify the status of the system.

In case the instrument is displaying an error, or the results of the simulator are out of specs, the LOM (laser optic module) of the CHM instrument shall be exchanged. It can be repaired and recalibrated in a lab.

Furthermore, on-site calibration in the field can be done to achieve absolute backscatter values from aerosol layers. The absolute calibration can be done in two different ways:

1) comparison with another lidar instrument, which should have a sensitivity 10 times better than the ceilometer and should have at least the same range resolution of 5m.

2) clear sky calibration and specific rain cloud calibration ( both methods will be implented by the European Met services shortly. There is an ongoing project to deliver the algorithms. Please check:

http://www.toprof.imaa.cnr.it/index.php/short-term-scientific-mission/8-1-short-term-scientific-mission
http://www.toprof.imaa.cnr.it/images/toprof/working_group/TOPROF_WG1_2015_UpdatedWorkPlan.pdf

Advantage: The Rayleigh calibration and the cloud calibration method do not need additional equipment.

The on-site calibration takes 24 h to 1 week to be able to compare different cloud and aerosol layer situations. In a rainy season, in permanent low cloud, brown cloud or in foggy places the on-site atmospheric calibration might not work at all, and our cloud simulator check of the lab calibration gives you the best result.

A new firmware version for the CHM 15k comes in two hardware-dependent variants: 

• Firmware version 0.xxx_550 (e.g. 0.743_550)

• Firmware Version 0.xxx_552 (e.g. 0.743_552)

The version 0.735_552 and all subsequent versions X.XXX_552 apply to newer CHM 15k devices which have been built since June, 2015. From the installed firmware version 0.733 on, you can find the right update version through on the CHM web interface.

For devices with firmware versions before 0.733, you can recognize the compatibility by means of the OS version (web interface --> device tab "firmware"):

For OS: 12.12.1 please use the firmware version 0.735_550 and for OS: 15.06.1 the firmware version 0.735_552.

If you have uploaded the wrong version accidentially, the status bit 12 is set. You can install the appropriate version again.

You can find the new firmware in the download area of the CHM 15k product page.

Depending on the degree of soiling of the windows, a corresponding NetCDF variable (state_optics) is reduced from its original value of 100. A warning is issued when a certain limit value (70) is reached and the status code of the device is changed. This can be used as a recommendation for cleaning the windows.

The overlap data corresponding to your device can be sent to you in the form of a file. Please contact us at service@Lufft.com.

A distance of 50 cm between the instruments is sufficient, provided that the levelling screws in the base of the instrument ensure a mutual tilting of 0.5°.

The case side with the door should face south, especially if the CHM15k is tilted due to steep sunlight (usually towards north).
This applies to the northern hemisphere. For the southern hemisphere, the opposite directions apply.

Please note that at an angle of solar radiation < 15° to the vertical, the device must be tilted in order to protect it against extreme solar radiation. We offer an angle adapter as an accessory for this purpose. Please feel free to contact us about this topic.

As of firmware version 1.020, the web interface / page "Process Status" displays the server name, status of availability, current time offset, query interval, etc.
Note: If the time delay is more than 1000 s (approx. 17 minutes), the time must be set manually via the web interface or the device must be restarted. If the NTP server can be reached, the time is immediately reset and not iteratively adjusted.

A 50 m (164') version can be offered. For longer lengths (e.g. 100 m (300')) we recommend using the standard version with 10 m (32') and e.g. to extend the main cable with sufficient cable cross-section (e.g. >= 2.5 mm²) via an installation box near the device.

The data cables for LAN and RS485 can be selected in shielded and twisted versions. We do not recommend LAN cables >100 m (300') without appropriate amplifier elements (e.g. Extender). RS485 cable lengths up to 500 m (1640') are possible with appropriate cable quality. Data connections >1 km (3280') are also possible through the use of DSL modems.

For sufficient lightning protection, the grounding cable should always be connected in the immediate proximity of the device.

Please contact us if you have any further questions or you are interested in a quote.

The CHM15k can be configured, restarted and shut down conveniently and password protected via the RS485 interface as well as via LAN/WAN and web interface.
Both the firmware and the operating system are restarted via 'restart system'.
Via 'shutdown system' the complete system is shut down and must be switched on again for a restart on site. Please take this into account, especially if the device is not installed in the immediate vicinity.
Please find a detailed description of the functionality in the manual.