Kipp&Zonen COMBILOG Data Logger - Manual (Page 31)

4.4 Internal Reference Voltage, Offset- and Drift
Correction
An internal reference voltage serves to adjust the entire ana-
logue signal processing automatically.
Especially for measurement of extreme low voltages, currents
and resistances, the configuration software features an addi-
tional compensation of temperature drift. With current- and
voltage measurement, this is realized by an internal offset
measurement. The measured offset is subsequently applied to
correct the measured values. For Maximum accuracy with cur-
rent measurement (temperature drift less than 25 ppm/K) it is
recommended to accomplish the measurement via an external
shunt with a correspondingly low temperature coefficient (< 5
ppm/K). For this purpose, the input channel has to be con-
figured as a voltage input.
For resistance measurement, a drift correction requires an ad-
ditional input channel which has to be equipped with a suitable
reference resistance. This resistance should have a low tem-
perature coefficient (< 5 ppm/K). In the configuration table, this
channel has to be defined as a reference channel with resist-
ance input for drift correction, whereby the nominal value of this
resistance (at 20°C) has to be indicated.
Using the above described methods, the analogue inputs can
almost completely be kept free from temperature drift.
Hardware Manual COMBILOG 1022
31