SCIENTIFIC AND THERMAL PREPARATION, ELECTRICAL TEMPERATURE CONTROLS AND COAL PRODUCTION DEVICES

摘要

A dual-slope measuring circuit for measuring an unknown resistance. A first time measurement measures the time which is needed to charge a capacitor to a first reference voltage (Uref1) via a reference resistor. A second time measurement measures the time which is needed to charge the capacitor again to the first reference voltage (Uref1) but now via the parallel arrangement of the reference resistor and the unknown resistance. The value of the unknown resistance is determined from the ratio between the two time intervals thus measured. The time measurement is not started until the capacitor voltage (Uc) on the capacitor has passed a second reference voltage (Uref2), where the second reference voltage has a value between the first reference voltage and the capacitor voltage (Uc) appearing across the capacitor immediately after discharge of the capacitor.