Celestron CG-4 User Manual download pdf (Page 6)

GENERAL INFORMATION

1 GENERAL INFORMATION

1.1 INTRODUCTION

Pyrgeometers are recommended by the BSRN (Baseline Surface

Radiation Network) as the best means of measuring the upward and

downward components of long wave atmospheric radiation.

CG 4 has been designed for meteorological measurements of

downward atmospheric long wave radiation with extreme high

reliability and accuracy. A second CG 4 can be used to measure the

upward component of the radiation.

Outdoors CG 4 provides a voltage that is proportional to the net

radiation in the far infrared (FIR). By calculation, downward

atmospheric long wave radiation is derived. For this reason CG 4

embodies a thermistor to measure the body temperature.

CG 4 uses a specially designed silicon window. Although the window

is not hemispherical, CG 4 has a 180° field of view with good cosine

response. A diamond-like coating protects the outer surface of the

window. On the inside a solar blind filter blocks all solar radiation.

The solar radiation absorbed by the window is conducted away very

effectively by a unique construction. Even in full sunlight the window

heating effect is very low compared to that of other pyrgeometers on

the market. This allows accurate daytime measurements without the

need for a tracking shading disc. It also eliminates the need for

window heating compensation by using the correction formula.

CG 4 features are:

• Sensitive to infrared radiation in a wavelength range from 4.5 to

approx. 40 µm.

• Low window heating offset.

• 180 ° field of view with good cosine response.

• Diamond like coating for optimal protection against

environmental influences.

• Low temperature dependence of sensitivity

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Celestron CG-4 User Manual Page 6