Transfer calibration system

Abstract

A method and apparatus for calibrating a liquid level measurement system of the type having capacitive sensors, by simulating the electrical effects of sensors in an empty condition and their interconnecting cables, at a time when the sensors are full or partially filled. By a sequential balancing technique, using a conventional bridge circuit, a precision, highly stable variable impedance device is adjusted to individually simulate the effects of each sensor and cable combination with the sensor in an empty condition. The settings of the variable impedance device are recorded, and at a later time when the sensors are no longer empty, these settings are reproduced, so as to recreate the electrical effects of each sensor cable combination one at a time. The individual effects are separately transferred into a network having a plurality of variable impedance channels, until each channel simulates the effects of a corresponding sensor and cable. This allows all of the earlier characterized effects to be simultaneously imposed on the measurement system.