ZYP—An Automatic Impedance mad Admittance Plotter
Harry A. Schenck · The Journal of the Acoustical Society of America · 1963
A versatile instrument for measuring and recording complex impedance and admittance has been constrncted. A variable-frequency two-phase oscillator supplies a reference signal to the unknown immittance and reference and quadrature signals to a two-channel synchronous detector. For the measurement of impedance, a constant current is supplied to the variable load, and the voltage across the unknown is applied to each channel of the synchronous-detector. The two filtered dc-output voltages are then proportional to the real and imaginary parts of the unknown impedance. For the measurement of admittance, a constant voltage is supplied to varying loads, and the current through the unknown becomes the input signal to the synchronous detector. The present model of the Z-Y plotter (ZYP) was constructed for the measurement of driving-point immittance of electroacoustic transducers. For unknowns whose impedance magnitude ranges from 100 Ω–100 kΩ, either impedance or admittance can be measured and plotted as a function of frequency between 30 and 30 000 cps. Full-scale deflection on any range was made to correspond to 10 μW power dissipated in a resistive unknown, but operation at other power, voltage, or current levels could be achieved. ZYP can also be adapted to measure complex transfer functions. [This research was supported in part by funds made available under a contract with the U. S. Office of Naval Research.]