Improved accuracy for the CA 2 Laboratory Thermopile

Improved accuracy for the CA 2 Laboratory Thermopilearticle picture
Published: Monday, November 7, 2011 For a number of years we have been calibrating the CA 2 against an old CM 1 pyrheliometer. Due to important feedback from one of our respected customers, received via our customer support module, we have lately been investigating the possibility to improve the current calibration procedure. This resulted in a new calibration procedure against a CHP 1 pyrheliometer, calibrated yearly in Davos against an instrument of the World Standard Group.

Laboratory thermopile CA 2 measures radiant fluxes and is sensitive to radiation from 0.2 to 50 µm. It is very suitable for control or demonstration purposes and can be used for reference measurements. Now that the new calibration procedure has been implemented the CA 2 can very well be used in scientific studies too.

With the new procedure the CA 2 will now be compared against a reference CHP 1 pyrheliometer in a horizontal parallel beam of light from a Xenon lamp at an irradiance level of 100 (+/-1) W/m2 in a room temperature environment. A better defined interchange of place will increase the stability and decrease the uncertainty of the calibration itself and therefore the accuracy of the measurement.

The calibration certificate was also updated. It will now be issued in the same format as that of our other solar instruments. It includes details of the calibration procedure, traceability and calibration uncertainty.  On the certificate two sensitivities will be displayed; S1 and S2. The first sensitivity represents the calibration factor for homogeneous irradiance falling on the front window and S2 represent the calibration factor for a beam of radiation falling only on the absorber (small beam).

For an example of a CA 2 calibration certificate click here.

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