Circuit Arrangements for the Measurement of Admittances, Impedances or Transfer Functions of Networks or Devices

1,152,068. Measuring impedance or transfer function. FUNKWERK DRESDEN VEB. Dec.7, 1966, No.54675/66. Heading G1U. A measuring circuit arrangement for automatically indicating couplex two terminal or four terminal parameters such as admittance, impedance or transfer function has three branches meeting at a junction 23, one branch including the test component 3 and the others including a standard conductance 1 and a standard susceptance 2. High frequency signals derived from a source 4 and modulated at 9,8 and 10 at different frequencies W3, W1, W2 respectively are fed into these branches via the transformers 6, 5 and 7. A high frequency quadratic demodulator 14 receives the sum of the voltages across the three branches and the output from this is passed to three channels 15,16,17. Selective amplifiers 15 and 16 select signals at the frequencies W 1 +W 3 and W 2 +W 3 respectively which are proportional to the real and imaginary components of the parameter being measured. These signals are rectified at 18,19 and displayed on a metering or cathode ray display arrangement 21. The selective amplifier 17 produces a signal at a frequency 2W 1 or 2W 2 which after rectification at 20 is used to control an attenuator V determining the magnitude of the applied high frequency signal, in accordance with the factor which relates the frequency terms to the actual parameter values, so that the indicator 21 reads these values directly. Four terminal networks are tested by connecting them between transformer 6 and the common point (53, Fig.2, not shown).