Apparatus for detecting error direction to establish the balanced state of a bridge circuit

Claim 1

An automatic balancing system for a bridge circuit which includes an element under test and a pair of variable elements, the system comprising: a source of test signal connected to the bridge circuit; means connected to a bridge circuit for producing an output signal therefrom representative of the balance condition of the bridge circuit; phase separator means connected to receive the output signal for providing first and second signals which are selectively separated in phase; sources of first and second reference signals, said first reference signal having greater magnitude than said second reference signal; first and second level comparator means, each connected to receive the first and second reference signals and the first and second signals for producing first and second control signals, the first control signal being representative of the first signal having attained a value between first and second reference signals, and the second control signal being representative of the second signal having attained a value between the first and second reference signals; and control means coupled to variable elements of the bridge circuit for sequentially altering the elements therein in response to said first and second control signals to converge the balance state of the bridge circuit on null.