An Algorithm for obtaining immittance or impedance loops

Abstract

An immittance loop algorithm has been developed for automated sonar transducer testing. This algorithm produces an excellent loop given only two frequencies separated by a resonance. Measurements of impedance and phase are made at increasing frequencies until the difference between the last recorded phase value and the current phase value approaches a calculated phase increment. At this point the new data are recorded and a new phase increment is calculated. Measurements continue for increasing frequencies until the specified upper frequency is reached. When plotted as a loop, the recorded data can be used to determine resonance frequencies, bandwidth, and other properties of resonant circuits. The algorithm has been implemented on two computer-controlled measurement systems with excellent results. Benefits of this algorithm include measurement of devices that have multiple resonances, measurement of high-Q devices, wide frequency range of operation, very efficient use of data space, and ease of implementation. The algorithm and its limitations are discussed, and sample programs and output are presented. [Work supported by NAVSEA.]