Resistance bridge measurements using micro-computer - measuring discharge time of capacitor which has been connected to imbalance voltage

摘要

The diagonal voltage on a resistance bridge (1) charges a capacitor (10) for a precise number of micro-computer clock pulses. The capacitor charge is thus an integral of the imbalance voltage. Identical resistors (15,16) are then switched in paralle with two arms of the bridge for the same number of clock pulses. The capacitor is then disconnected from the bridge, and the voltage across it is amplified and fed to window-discriminators (7,8). If the voltage is zero, the micro-computer registers a balanced bridge. If the voltage is measurable, the cycle begins again, but the resistors are switched for dissimilar times. This is repeated for increasing time differences until the voltage at the end of a cycle is zero. The time ratio for this last cycle is a measure of the imbalance, which is then calculated by the micro-computer.