Self-calibration/compensation technique for microcontroller-based sensor arrays

Abstract
Described is a generalized technique for real-time gain and thermal compensation of embedded microcontroller-based sensor arrays. By incorporating a single or multiple low-cost, uncalibrated thermal sensor(s) into a software feedback loop, a self-normalized calibration/compensation table for each sensor can be generated and stored in EEPROM for later use in real-time signal acquisition. The compensation is accomplished by executing a one-time initialization software routine as the sensor array is cycled through the expected temperature range. To achieve compensation to within the system resolution, the required correction loop bit width will be different from that of the system bit width. In addition to temperature compensation, the technique also includes correction for gain and voltage offset errors introduced by the analog signal conditioning as well as A/D conversion errors. An example of the technique is presented using a 68HC711E9 microcontroller for real-time acquisition and compensation of a four-element strain gage array.

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