Abstract: A measuring circuit (MS) for measuring the value of an impedance in an impedance network includes an oscillator device (OSZ1), a second oscillator device (OSZ2), a phase-controlled rectifier (PG), a reference/actual value comparison point (AG) and an integrator.The first oscillator device feeds a first alternating voltage of constant amplitude and constant frequency to a first output connection (A1). The second oscillator device feeds a second alternating voltage of the same frequency, but with adjustable amplitude and with phase shifted by 180.degree., to a second output connection (A2). The amplitude of the second alternating voltage depends on the phase of the signal which is transmitted to the phase-controlled rectifier via an input connection (E). If the input signal is in phase with the second output signal, the amplitude of the second output signal is reduced. However, if the input signal oscillates in opposite phase to the second output signal, the amplitude of the second output signal is increased.

Abstract: An evaluating circuit for linearizing the output signal of a differential-choke displacement transmitter has two inductive coils each supplied with an alternating voltage with constant frequency produced by an oscillator, wherein the amplitude is adjustable and the second alternating voltage is phase-displaced relative to the first alternating voltage by 180.degree.. The signal which is picked up between the inductive coils at the input is compared, after a phase-controlled rectification, with a reference value and the deviation is integrated. With the aid of the integrated signal the regulation of the amplitude adjustment of the alternating voltages is performed. As a result a measuring signal without residual ripple is obtained, which changes proportionally to an adjustment path for example of an adjustment rod.