Pick=up system signal output stage - scans AC output signal, whose frequency depends on physical variable, at fixed frequency between set limits

摘要

The system picks up a physical variable and delivers an a.c. output signal whose frequency is characteristic of the variables. A digital frequency scanner (21) sfand the pickup system output signal at a specified fixed frequency fT which can be selected between a lower limit, a fraction of the lowest frequency fu to be detected, and an upper limit equal to the highest output frequency fo of the pickup system to be detected. The digital frequency scanner (21) consists of a D-flip-flop, to whose clock input (22) an alternating square wave signal with a scan frequency fT is applied. The output signal (41, 42) of the pickup system is applied to the D input of the flip-flop. The tuning output signal, tapped from an output of the D flip-flop, is the input signal on either the forward or back edge of the output impulse of the D flip-flop (21) pulse former stage.