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Drift Compensation in Data Acquisition Using the KPCI-3108 AutoZero Technique
by
Mike Bayda
Keithley Instruments, Inc.
Introduction
Measurement drift is one inherent attribute that all test and design engineers must address. Gradual zero drift, as well as
reference and gain drifts, are essentially caused by the effect of ambient temperature on electronics. Other factors such as
aging of electronic components, humidity, and pressure could also play a role in long term drift.
An intelligent analog design is very important for predicting and balancing potential drifts introduced by different components
in the circuit. A typical example is thermocouple measurement, which requires microvolts of sensitivity and high gain
amplification. Any small drift within the measurement device would lead to false temperature readings of the device under
test.
Advanced autozero techniques are typically available on benchtop instruments that address higher resolution applications
(more than 16-bit) and are usually equipped with autonomous processing power. On the other hand, most data acquisition
(DAQ) plug-in boards do not address this issue and are therefore more vulnerable to measurement drift.
The Keithley KPCI-3108 is a multifunction plug-in DAQ board equipped with accurate and precise measurement techniques,
including a programmable autozero capability that is designed to eliminate zero drift. This document discusses the KPCI-
3108's calibration details and shows how to use its autozero feature with DriverLINX