Kippzonen COMBILOG Data Logger User Manual download pdf (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.

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Kippzonen COMBILOG Data Logger User Manual Page 31