Celestron CG-4 User Manual download pdf (Page 38)

OPERATION

4.2 MEASURING NET RADIATION WITH TWO PYRGEOMETERS

With two CG 4’s as a net-pyrgeometer, the long wave radiation

balance (also called net long wave radiation) can also be measured.

This balance, combined with the information from an albedometer,

gives the net total radiation. A mounting plate with 500 mm rod for 4

possibly ventilated sensors is available (see chapter 9).

When determining the net-long wave radiation, it is not strictly

necessary to measure sensor temperatures.

Assuming that the temperatures of upper and lower sensor are equal,

it can be cancelled from the equation for net-radiation.

The combination of a net pyrgeometer (two CG 4’s) and a CM 7B or

CM 14 albedometer for measuring net total radiation has many

advantages over conventional net total radiation sensors with plastic

(polyethylene) windows. Robustness and maintainability are better,

separate information on solar and long wave radiation is offered.

Problems with dew deposition are minimised with the Kipp & Zonen

CV 2 ventilation unit by ventilating and optional heating of the

pyrgeometer.

4.3 THERMAL STRESS STUDIES

The CG 4 pyrgeometer is suitable for use in building research for

thermal stress studies. It may be necessary to keep the CG 4 body at

a known temperature, e.g. the human skin temperature, to get

reproducible results.

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Celestron CG-4 User Manual Page 38