Why is the Pyrgeometer from Kipp & Zonen so much better than those from the competition?
The CGR 4 differs from all other Pyrgeometers in that it allows accurate daytime measurements on sunny days without the need for a shading device. Due to the unique construction of the CGR 4, solar radiation of up to 1000 W/m² induces window heating of less than 4 W/m² in the overall calculated downward radiation. In the Baseline Surface Radiation Network (BSRN) manual (WMO/TD-No.897) an extended formula is described. This formula corrects for window heating and so called “solar radiation leakage”. Due to the very low window heating offset and optimal spectral cut-on wavelength, these corrections are not necessaire for the CGR 4.
What is the calibration interval of a pyrgeometer?
We advise to re-calibrate the Pyrgeometer every two years.
More information about our calibration service can be found here.
I am using a Ventilation unit on the Pyrgeometer. Do I need to put this on 5W or 10W?
If the CVF 3 is used for a Pyrgeometer the effect of sunrise is not valid and continuous 5 Watt is preferred. In extreme cold climates , polar / mountain tops, the 10 Watt heater can be used continuously.
How can I check if there are interferences from the cable?
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.
Negative output during nighttime measurements?
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.
Solar radiation at the site was greater than 1400 W/m²! Is this reasonable?
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.
What is the directional or cosine response?
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°).
What parameters or errors should we take into account if the source of light comes from a certain angle?
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
Can I use a pyranometer under water?
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.
If I use a pyranometer under water, can I connect a data logger to it ?
Yes, however the data logger needs to be placed on the surface (it is weather resistant, but cannot be lowered into the water).
What is the calibration frequency of a pyranometer?
We advise to re-calibrate the Pyranometer every two years.
What does spectral range of 310 – 2800 nm (50% points) mean?
The 50 % points are the wavelengths where the output of the instrument is 50 % reduced with 100 % input.
I am using a ventilation unit on the pyranometer. Do I need to put this on 5W or 10W?
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.
What is the WMO standard for the pyranometers?
What is the resolution of a pyranometer?
The instrument has an analog output, therefore the resolution is infinite. Every change is noticed, no matter how small it is.
What is the bandwidth of a pyranometer?
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
In our PV application the cable from the CMP 11 (50 meters) will go along other cables that come from the PV panels in which there is a DC voltage and around 100 Amps. Will these cables affect the measurement?
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.
Do you have filters that can be used to verify spectral distribution over the following wave lengths?
Ultraviolet - B 280-320 Ultraviolet - A 320-360 and 360-400 Visible 400-520, 520-640 and 640-800 Infrared 800-3000nm.
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.
Is there a standard product that converts the pyranometer output signal to 0-5V or 0-2V?
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.
What kind of pyranometer do you suggest for usage inside a greenhouse?
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.
What type of pyranometer can I use for my fixed PV panels farm?
CMP 11 is advised for this application. Please note that the pyranometer needs to be mounted in the same angle as the PV panel.
What type of pyranometer can I use for my solar concentrators farm?
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.
Is there a Pyranometer available that has the same spectral characteristics as a PV panel?
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.
Is it possible to connect the Pyranometers to a computer?
That way, I could, using software (if there is any available), measures solar radiation all the time, non-stop.
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.
I would like to know what kind of output the CMP 6 Pyranometer has (analog or digital)? What voltage range do you have?
The CMP 6, as with all our solar radiometers based on thermopiles has a continuous small analoge 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.
Do the pyranometers come with a calibration certificate, NIST traceable?
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:
What does Zero Offset A mean?
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 domes 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.
Are there any accessories needed with the Pyranometer to avoid reflected radiation from the surface?
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.
What is the big difference between CMP 11 and CMP 21?
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 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.
Does a Pyranometer require any power?
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.
Is it possible to mount 4 pyreliometers plus an extra sun sensor?
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.
How much power is needed for the 2AP?
The power use of the 2AP itself is about 1.5 A to 2 Amps. (internal fuse is 3 Amps slow)
What power supply is needed when heaters are used?
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
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)
Does the 2AP work autonomously?
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.
Can the tracker be connected to a PC at 30 m distance?
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.
Why does the COM port of my Pentium not address the 2AP like my old 4.86?
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.
What is the range of the temperature?
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.
What is the accuracy of the 2AP tracker in combination with a sun sensor?
The 2AP has the following errors:
- 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.
Is there a compensation for temperature drift?
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 cannot be compensated for in firmware.
Is compensation for pressure variations needed?
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 heath of operation. A value of 1000 mBar is typical for sea level.
Is there a way to fix a tracker via remote PC?
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.
Why is the altitude limited to 2000 m?
The 2AP BD altitude specification (2000m) is limited by the CE and CSA (Canadian Standards Association) recommendation for 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 24VDC, as this would eliminate the altitude restrictions associated with high voltage AC.
Can I measure specific parts of the UV spectrum with the CUV 4?
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.
What is the calibration frequency of UV radiometers?
We advise to re-calibrate the UV radiometers every two years.
Can a METEON or SOLRAD data logger be connected to UVS-A-T and UVS-B-T?
No, input range METEON limited to 200 mV (output UVS-X up to 3V)
What does ‘Mean Adjustment Factor’ mean on the calibration certificate of a UV radiometer?
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).
Is there an UV-C sensor available?
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.
I noticed that the UVS series has a temperature controller, which make it constant 25 ˚C. Do you think this controller can cover ‘automatic temperature compensation’?
Actually 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.
What is the bandwidth of the CUV 5 and why does this not match the UV spectrum?
The bandwidth of the CUV 4 is 280 - 400nm. The 50 % points are defined to be 290 - 385 nm.
What does ‘Radiation Amplification Factor’ mean?
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.
Can the UVIATOR software operate with a Campbell logger and its software? Or, do I have to use LOGBOX-SD for compatibility with UVIATOR?
The UVIATOR can work with any data logger that is capable of storing UVS measurements. The UV-data must to be stored in the correct format, and Campbell loggers can do this. More details can be found in the UVIATOR manual.
Why do I need the UVIATOR software?
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.
What is the output range of the UVS radiometers?
The UVS series of UV radiometers have an output in the range from 0 - 3 V.
Can the data from the CUV4 be used as input to calculate UV index?
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).
Does the UVS-AB measure UV-A and UV-B at the same time?
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.
Solar Instruments Accessories
Should I use a CVF 3 ventialtion unit in a warm environment and do I need a heater?
The CVF 3 increases the accuracy and maintenance interval by:
In the morning dew on the domes is prevented (ice in your region will be no problem)
Dirt (dust) deposit on the domes is less with ventilation
Zero offset is less because airflow keeps dome and body temperature closer together.
The use of the heater in the CVF 3 is not really necessary. (Although also dew is removed quicker)
Here the first item is really the most important one. If dew deposit is no problem the CVF 3 can be omitted.
How often should I clean the filters of the CVF 3 ventilation unit?
1) The filters are designed to use for a year in normal circumstances. Extreme circumstances like in factories with a lot of soot or chemical emission are a exception.
2) When they are dirty the filters can be washed out with water. After being dried a cleaned filter can last another year.
Can I order a new filter for my CVF 3 ventilation unit?
Filters can be ordered in sets of 5 (number 2682-916).
What is the accuracy calculation from a radiometer to the input of the AMPBOX? And the accuracy calculation out of the AMPBOX?
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.
What does “gain range” mean in the AMPBOX specification? And how is this value useful?
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.
In the AMPBOX specification what does “Zero adjust” mean? And how is this value useful?
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.
What is the benefit of using a ventilation unit?
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).
The ventilation unit has a 5 W and 10 W heater. When do I need 5 W and when do I need 10 W?
Advised is 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.
How can I enable the 5 W or 10 W heater option of my CVF 3 ventilation unit?
By applying power to pin 6 or 7 for 5 W and both for 10 W.
Can I convert the current output (mA) of an AMPBOX to Volt?
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 has a range of range 0 - 1600 W/m2 for 4-20mA. The CMP 3 pyranometer has a sensitivity of 16,51 μV/W/m². And the PQS 1 PAR quantum sensor has a sensitivity of 5,59 μV/μmol/m²s. How can we calculate the output signal?
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
0 μmol = 4 mA
295.35 μmol = 5 mA etc.
4725.6 μmol = 20mA as maximum input
Can we measure low level photosynthesis radiation (0,1 μmol/m²s) with the PQS 1 and the AMPBOX?
No, 0,1 μmol/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.
Can I use a METEON data logger in combination with the AMPBOX?
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).
Each AMPBOX corresponds to a specific pyranometer, could you please specify this?
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.
What color code is used when there is an extended cable on the NR LITE?
Sometimes it happens that the colors of the cables are different when you order extended cables. Usually there is added a page in the manual where this is mentioned.
Standard = extended
White = white
Green = blue
Black = black
For the NR Lite, we want to use wind correction, but we don't understand the manual
The correction factor in the manual could indeed be written more carefully. It says dividing by (1+x.V3/4) this refers to the calibration factor. Better is to say the output should be multiplied with a factor (1+x.V3/4).
For the CNR 1, what is the ideal constant current source for the PT-100?
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) also 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 2ºC (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.
What is the response time for CNR 1 sensors?
Response time for CNR1 sensors: 5 s (63%) en 18 s (95%)
Does the CNR 2 use the same sensor as the NR Lite(2) without wind-breaking domes? Or does it have separate thermopiles for short and long wave radiation?
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.
How come the NR Lite(2) specs refer to a continuous range between 200 and 100,000 nm, while the CNR 2 specs refer separately for the short and long wave radiation ranges?
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.
What is the extension of the log file of the LOGBOX SD?
The extension is .TXT or .XLS. Using the software interface you can select to save this as a text -or Excel file.
What is the format of the log file of the LOGBOX SD data logger?
The format uses columns, for example:
How do I connect a Pyranometer with PT100 to the LOGBOX SD Data logger?
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.
Does the internal battery stop working when you power the Logbox SD with an external power supply?
In this case, will you still have power available for excitation on the Power Out connection?
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.
How does a data logger work?
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 ).
Can I use the METEON in combination with the AMPBOX?
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).
Can the data from the METEON be downloaded into Excel?
Yes, inside the software, at the graphical chart, there is an export button. You can select the default .txt option or customize the extension into .xls.
Can a METEON data logger be connected to UVS-A-T and UVS-B-T?
No, the output of the UVS is 0-3V and this is too high for the METEON.
What is the logging interval for the METEON?
The logging interval can be selected from 2 to 65.535 seconds.
What is the operating life of the batteries of the METEON?
Two AA size internal Alkaline batteries will operate for approximately 1200 hours / 50 days.
How is the METEON powered?
With two AA size internal Alkaline batteries.
Can we use the METEON outside?
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.
What is the difference between the SOLRAD and the METEON?
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.
I have an outdoor reading of 2000 to 4000 W/m² with my METEON. This does not make sense since theoretically, readings should be less than the solar constant (1360 W/m²).
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.
If we take an interval of 1 minute then the sum of all the averages for 1 day it says 394838 W/m². If we set it for 30 minutes, then we will get 1 average per 30 minutes so the sum of all these averages for 1 day would be 13161 W/m².
What are we doing wrong?
Adding the intervals without dividing this by the (interval) time.
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
Can a SOLRAD data logger be connected to UVS-A-T and UVS-B-T?
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.
How can we program the SOLRAD for the output to be in W/m² ?
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.
I understand the SOLRAD is not really a data logger. Is this correct?
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.
How is the SOLRAD powered?
The internal battery will only run it for a little more than one day. For longer periods it requires an external DC supply.
Can we use the SOLRAD outside?
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.
How long can I record data on my COMBILOG data logger
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.
Is there a table with the amount of water that we need to irrigate in one hectare, according the readings of the PQS 1 PAR quantum sensor (PAR Lite) daily?
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.
With the PQS 1 (PAR Lite), can I derive the crop evaporation from the net radiation?
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 don't have the information how to do it. 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 the metoffice gives such figures for your area it should be of importance 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.
How many PQS 1 PAR quantum sensors (PAR Lite radiometers_ do you advise to use in a greenhouse?
Normally 1 should be enough. If in the greenhouse the conditions differ, like different glass type, shielding or glass cover, it is advised to use more than one PQS 1 PAR quantum sensor per typical condition.
Can I use a PQS 1 (PAR Lite) meter under water?
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.
If I use a PQS 1 PAR quantum sensor (PAR Lite radiometer) under water, can I connect a data logger to it?
Yes, however the data logger needs to be placed on the surface (it is weather resistant, but cannot be lowered into the water).
What is the advised calibration frequency for a PQS 1 (PAR Lite)?
We advise to re-calibrate the PQS 1 (PAR Lite) radiometer every two years.
PAR readings at noon increase by the order of 0.001 umol/m²s. Can you tell me whether small readings like this are likely to be accurate? If not, what is the effective lower irradiance limit detectable by this sensor?
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 linearity, temperature dependence and the quantum response. Measurements under 1 µmol/m²s are not to be trusted as accurate. (effective limit)