Capacitive bridge measurement circuit - has square wave bridge supply and diode voltage reference providing temp. compensation

摘要

A measurement device has a capacitive measurement bridge with two variable capacitors in series supplied from an alternator. The output voltage is taken from the capacitor junction and the input to a detector circuit. The arrangement is applicable to vehicle headlamp position measurement where the suspended mass is ascertained w.r.t. the vehicle framework. It has original temp. compensation. A square wave generator (1) provides the a.c. voltage to the bridge capacitors (2a,2b). It contains an operational amplifier (1) connected as a comparator with its negative input connected to a reference voltage via a capacitor (12). A potential divider (8,9) provides a more positive d.c. voltage to the amplifier's positive input. The capacitive bridge output is connected to a peak value detector circuit (3) and a reference voltage diode (D1) conducting towards the output junction.