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

More information about our calibration service can be found here.

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 is cooling 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 is cooling 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 Ventilattion 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.

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 1 meter 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 2 meters. 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).

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

We advise to use the 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 could be sufficient. Below zero degree Celsius the extra 5 Watt (10 Watt total) can be used. We recommend to use 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.

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

There are some exceptions:

• 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 problem is to be expected.

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 PAR Lite  is advised.  CMP 6 for outside usage to measure Global solar radiation. Par Lite to measure  PAR radiation inside which is most sensitive for plants and crops.

CMP 11 is advised for this application. Please note that the pyranometer needs to be mounted in the same angle as the PV panel.

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.

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

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

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

The CMP 21 is individually tested and the temperature compensation is optimised.  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. 

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 30 meter. We can supply this cable, but it can be bought "around the corner".

The communication software is included with the 2AP.

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 2 are user controlled and the last 2 are fixed.

Assuming that the leveling is done 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 5 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 on a regular interval there is no need for a sun sensor. If however this interval can or will not 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 2 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 base (drying cartridge and dirt on domes).

Better than giving an error in percentage we would like to show the benefit of not having to correct to clock. 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.

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

For easy correction for solar zenith angle and Ozone column.

This is required because these two factor 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.

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 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.

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.

By applying power to pin 6 or 7 for 5 W and both for 10 W.

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, 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).

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 I sin 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.

The format uses columns,  for example:

The picture shows how a PT100 is connected.  PT100 uses four input channels nr 1,2 ,3 and 4. Leaving 4 channels left, nr 5,6,7, and 8, to connect other sensors.

Please note that the picture uses 2 analogue inputs for the instrument (differential). Of course you can decide to use it single ended, by connecting the – from the instrument to the GND.

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 of the battery.

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

Every logger has an A/D converter with a certain resolution (number of bits) - often 10, 12, 16 or 24 bits resolution.  A logger also has a fixed number of analog input ranges - often 20 mV, 100 mV, 1 V, 5 V and 10 Volt ranges.

For example we use a logger with 12 bits resolution and 5 Volt  input range.
This means that the 5 Volt is divided in 2¹²  steps. This is 5/4096 = 0.00122 Volt per step. So the smallest detectable change on the input is 1.22 mV.

If we connect an SP Lite(2) with a sensitivity of 75 microVolt/W/m^2, one Watt (change) will give 0.075 mV (change) on the output. So we need a change of 1.22 / 0.075 = 16.2 Watt/m² before we see a change in the Logger output.

As you can understand this is not acceptable. A minimum of 1 W/m² should be detected (preferably a factor 10 times better). This can be achieved by lowering the input range to 100 mV (50 times better). Or by selecting a higher resolution e.g. 16 bits (in stead of 12 bits) this is 16 times better ( 2¹⁶- 2¹² = 2⁴ = 16 ).

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.

This depends on the number of recorded channels and storage interval. A detailed description of the storage capacity can been found in the COMBILOG manual, available on it's product page.

In case you want to quickly calculate the storage capacity in days for your application, please use the calculation tool below.

Yes, however the depth is limited to 2 meters. Please also take the “breaking of light on the water surface” in consideration. This affects the calibration factor.