Kipp&Zonen CM 4 Pyranometer - Manual (Page 25)

24
Figure 3.1: Circuit diagram of the CM 4 Pyranometer and connection to
readout equipment.
It is evident that application of attenuator circuits to the CM 4 output
in order to modify the calibration factor is not recommended because
the temperature response will also be affected. However, recorders
with a variable voltage range can be set so that the result can be
read out directly in W/m
2
.
A considerable input bias current in the readout equipment can
produce a voltage of several micro-volts across the impedance of the
pyranometer. The correct measured zero signal can be verified with
a resistance replacing the pyranometer impedance at the input
terminals.
With the availability of a low voltage analogue input module with A/D
converter the pyranometer can be connected to a computer or data
acquisition system. The span and resolution of the A/D converter in
the module must allow a system sensitivity of about 1 bit per W/m
2
.