CM4 Pyranometer

  • Heat resistant instrument design
  • Extended operating temperature range
  • Excellent temperature dependency
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CM4 Pyranometer

The Kipp & Zonen CM4 High Temperature Pyranometer is a radiometer specially designed for measuring solar or artificial light irradiance under the most extreme temperature conditions.

With an operating temperature range of -40 ºC to +150 ºC and measurement up to 4000 W/m² it is a unique product. All the radiometer components are specially selected for their ability to withstand these extremely high temperatures and irradiance. The CM4 is supplied with a 10 m high temperature signal cable fitted to the instrument.

The CM4 High Temperature Pyranometer has internal first-order temperature compensation, but it is also supplied with a built in Pt-100 temperature sensor to provide additional information on the measurement conditions. Monitoring the temperature during operations allows easy data correction afterwards for improved measurement accuracy.

CM4 is supplied with a calibration table that gives the instrument sensitivity for a number of measurement temperature ranges and the maximum error in the measured irradiance values within each range.

The screw-in drying cartridge is easy to remove and the replacement desiccant is supplied in convenient refill packets.

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Specifications

Spectral range (50% points) 300 to 2800 nm
Sensitivity 4 - 10 µV/W/m²
Response time < 8 s
Zero offset A < 4 W/m²
Zero offset B < 15 W/m²
Directional response (up to 80° with 1000 W/m² beam) < 20 W/m²
Temperature dependence of sensitivity (over any 50 °C interval in the range from -20 °C to +150 °C) < 3 %
Operational temperature range -40 °C to +150 °C
Maximum solar irradiance 4000 W/m²
Field of view 180 °

FAQ

  • 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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