Digital liquid-level gauging systems

摘要

A liquid-level gauging system comprises a capacitive probe arranged in a liquid storage tank and electrically connected into timing circuitry of a pulse generator to render the period of the pulse output produced by the generator directly proportional to the probe capacitance and thus proportional to the level of liquid in the tank. The generator pulse output is used to gate a counter receiving pulses from an oscillator whereby, for each cycle of the generator output, an accumulated count is produced in the counter which is proportional to the cycle period. This count is a proportionate measure of the liquid level. The count can be used as an address code for a read-only memory such that the memory output is the number stored in the memory at the address represented by the count value. Suitable programming of the memory can thus give any desired relation between count value and memory output and therefore any desired relation between memory output and tank liquid level.