Multilevel liquid sensing system

Claim 1

a multilevel liquid level sensing system comprising: a flat cable sensing probe assembly having a plurality of probe conductors whose lower ends are at different discrete levels in a container for liquids; resistance bridges each comprised of a pair of said probe conductors connected with three fixed value resistors, the third resistor so that the state of the bridge is known with both probe conductors out of the liquid; means for supplying a train of low duty cycle dc interrogation pulses in parallel to said resistance bridges and hence to said probe conductors; integrated circuit voltage comparator signal detectors each of which has a binary output and inverting and noninverting inputs connected across one of said resistance bridges such that the output is in one state when the lower ends of both probe conductors are in or out of the liquid, and is in the other state when the lower end of one probe conductor is in the liquid and the lower end of the other probe conductor is out of the liquid, said binary outputs in combination indicating the different discrete liquid levels; storage means for said binary outputs which are read out between said interrogation pulses to timing logic means to achieve a continuous liquid level control; said timing logic means comprising a timer which measures the time for the liquid to rise or fall between two adjacent discrete levels, and a flow rate calculator which monitors the flow rate of liquid between the two discrete levels.