Linearising circuit for measuring probes - uses summing amplifier with decade selector switch for matching non:linear characteristics

摘要

The linearising circuit for measuring probes with nonlinear characteristics consists of a zener diode-stabilised voltage source across which is connected a first operational amplifier. The sensitive measuring element (e.g. resistance thermometer) is connected in the amplifier feedback loop. The output of a second amplifier at a slope of about 30m V/deg.C is connected to the non-inverting input of the output amplifier. Two voltage-follower amplifiers are fed from decade selector switches connected to precision resistors across the supply. The second bank of the ganged selector switch connects further resistors in the feedback loop of another operational amplifier which drives the output amplifier. A point-slope matching of the summing amplifier gain to the non-linear sensor characteristic is thus obtained.