CMP21 Pyranometer

  • ISO 9060 Secondary Standard
  • Verified cosine response 
  • Verified temperature dependence
  • Low dome IR offset error
  • Excellent linearity
  • Fast response time
  • 5 year warranty (*)

 

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CMP21 Pyranometer

The CMP21 is a high performance research grade pyranometer, and is fully compliant with all ISO 9060:1990 Secondary Standard Instrument performance criteria (highest possible ISO pyranometer performance category).

The CMP21 pyranometer is designed for measuring the irradiance (radiant flux, Watt/m²) on a plane surface, which results from the direct solar radiation and from the diffuse radiation incident from the hemisphere above.

CMP21 has the same detector as the CMP11 and individually optimised temperature compensation. A standard thermistor sensor is fitted to monitor the housing temperature. Each instrument is supplied with its own temperature and directional (cosine response) test data.

It is the choice for scientific use and in top level solar radiation monitoring networks such as the BSRN (Baseline Surface Radiation Network) of WMO.

A waterproof socket is fitted for the signature yellow signal cable, which is available in a range of lengths pre-wired to the waterproof plug. The integral bubble level is raised to the top of the housing and can be viewed without removing the redesigned snap-on sun shield, which also covers the connector. The screw-in drying cartridge is easy to remove and the replacement desiccant is supplied in convenient refill packets.

The pyranometer does not require any power, it supplies a low voltage of 0 to 20mV in relation to the amount of incoming radiation. When a higher voltage level or a 4 to 20mA signal is required, the AMPBOX is the perfect solution.

(*) This product will need to be registered by the end-user within 6 months of purchase to activate the warranty extension.

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Specifications

Spectral range (50% points) 285 to 2800 nm
Sensitivity 7 to 14 µV/W/m²
Response time 5 s
Zero offset A < 7 W/m²
Zero offset B < 2 W/m²
Directional response (up to 80° with 1000 W/m² beam) < 10 W/m²
Temperature dependence of sensitivity (-20 ºC to +50 ºC) < 1 %
Operational temperature range -40 °C to +80 °C
Maximum solar irradiance 4000 W/m²
Field of view 180 °

FAQ

  • The colour of the desiccant in the pyranometer was nearly transparent and not orange.
    • Kipp & Zonen states that the replacement of the (external replaceable) desiccant for their radiometers can be done at 6 months intervals. Even in humid environments the desiccant is guaranteed for at least 6 months, so no condensation takes place inside the instrument. A good practice is to combine checking the desiccant and the leveling of the instrument and cleaning the dome.

      The color change of the desiccant beads takes place from orange to transparent at 6% weight absorption at 40% relative humidity. The maximum weight absorption is 23% at 40% rH. This means that even after the desiccant color has changed to transparent the beads are still active.

      Desiccant beads can be easily exchanged by using refill packs. To compensate for a long storage interval before installation, extra desiccant packs are provided. Alternatively the beads (not the cartridge) could be regenerated by drying in an oven at 120°C (several hours) until the color has changed back to orange.

      Kipp & Zonen introduced the CMP/SMP10 with CMP/SMP11 specifications but with enough internal desiccant(molecular sieve) for 10 years to solve the issue of the external desiccant.

      http://www.kippzonen.com/Download/902/Technical-Advise-Desiccant-replacement-interval

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  • 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.

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  • What kind of services do you provide for the CMP21?
    • CMP21 Conventional Pyranometer (External drying cartridge)
      Part number: Description: Extra information:
      0338750 Inspection Full inspection + inspection report.
      0999910-1 Sensitivity calibration Indoor calibration against traceable reference.
      (New calibration certificate will be supplied)
      0999930 Directional error test Measured at four zenith angles and four azimuth angles
      0999920-1 Temperature profile From -20°C to +50°C in eight steps of 10°C
      0999920-2 Temperature profile From -40°C to +50°C in ten steps of 10°C
      9016381 Sunshield
      0016400 Leveling screw
      0016401 Fixed foot
      0362702 Drying cartridge kit Kits include cartridge, lid, o-ring and 2 bags of desiccant.
      2643960 Desiccant refill pack 10 Sachets
      0362417 Outer dome kit Mounted on ring and includes fixing screws and o-ring seal.
      2523145 Waterproof 4-pin plug For 10K version
      0362611 Waterproof 4-pin plug +10m cable For 10K version
      0362613 Waterproof 4-pin plug +25m cable For 10K version
      0362614 Waterproof 4-pin plug +50m cable For 10K version
      0362615 Waterproof 4-pin plug +100m cable For 10K version
      2523146 Waterproof 8-pin plug For Pt-100 version
      0362621 Waterproof 8-pin plug +10m cable For Pt-100 version
      0362622 Waterproof 8-pin plug +15m cable For Pt-100 version
      0362623 Waterproof 8-pin plug +25m cable For Pt-100 version
      0362624 Waterproof 8-pin plug +50m cable For Pt-100 version
      0362625 Waterproof 8-pin plug +100m cable For Pt-100 version
      0362774 Replace outer glass dome Factory repair (new dome will be fitted)
      0362771 Replace inner glass dome Factory repair (new dome will be fitted)
      0362752 Replace bubble level Factory repair (new bubble level will be fitted)
      0362790 Replace 10K thermistor Factory repair (new 10K thermistor will be fitted)
      0362791 Replace Pt-100 Factory repair (new Pt-100 will be fitted)
      0362762 Replace detector Factory repair (new 10K detector will be fitted)
      0362763 Replace detector Factory repair (new Pt-100 detector will be fitted)
      0999911 Replacement calibration certificate Please provide serial number and instrument type.
      0362100 Large radiometer fixing kit Fixing kit
      0999910-3 Sensitivity calibration ISO17025 Calibration can only be done between april and september.
      0305722 Glare screen kit For downwards facing setup.

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  • 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

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  • 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).

       

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  • What is the calibration frequency of a pyranometer?
    • We advise to re-calibrate the Pyranometer every two years. 

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  • 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.

      spectral range

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  • What is the WMO standard for the pyranometers?
    •  

       

      CMP 3

      CMP 6

      CMP 11

      CMP 21

      CMP 22

      WMO

      Moderate quality

      Good quality

      High quality

      High quality

      High quality

      ISO

      Second Class

      First Class

      Secondary Standard

      Secondary Standard

      Secondary Standard

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  • 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.

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  • 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

      Solar Irradiance Spectrum 

       

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  • 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.

       

       

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  • 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.

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  • 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.

      Output signal pyranometer

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  • What kind of pyranometer do you suggest for usage inside a greenhouse?
    • 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.

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  • What type of pyranometer can I use for my fixed PV panels farm?
    • For this application the CMP10 and SMP10 are advised as they have an internal drying cartridge that will last for at least 10 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 visible Kipp & Zonen offers the CMP11 and SMP11 with visible and user changeable desiccant.

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  • 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.

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  • 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.

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  • 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.

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