Ridge circuit compensation for environmental effects

Abstract

A method and apparatus are described for using a computer to compensate for zero point and span errors as well as other non-linearities in the operation of strain gauge transducers. The apparatus comprises a semiconductor strain gauge transducer with a quasi stable voltage supply, two strain gauges and two precision resistors which form a voltage divider network; a scanner for scanning the strain gauges and precision resistors; an analog-to-digital converter for digitizing the output of the scanner; and a microprocessor for calculating a corrected output representing the phenomenon that is monitored by the strain gauge transducer. The microcomputer contains a memory in which are stored a set of bridge completion constants, a table of correction constants and a set of temperature compensation and signal conditioning algorithms. The bridge completion constants are a set of values representative of the bridge supply voltage and the resistances of a set of bridge completion resistors which are selected during factory calibration to provide two point temperature and two point span compensation for the pair of strain gauges used in the transducer. One group of correction constants provides for zero point compensation over the operating temperature range of the transducer, a second group provides for span compensation and a third group compensates for other input to output non-linearity.