Measurement of Amplitude Frequency Response of a Transformer - A Simple, Automatic and Time-Efficient Procedure

Abstract

Amplitude frequency response of a system is required to be measured for several purposes. Typically, the measurement takes several hours to complete, when done manually by varying the frequency of the input signal in discrete steps and recording the system’s response. The commercial equipment meant for this job require only some minutes. However, they are often expensive and not so common in all laboratories. To alleviate this problem, an automatic, fast and easy-to-implement approach for measuring amplitude frequency response (i.e. transfer or driving-point function) of a system is described. A function/arbitrary waveform generator and a digital oscilloscope are the only instruments required, and these are readily available in all labs. The most crucial aspect of the approach is to synchronously trigger both of them, with the function generator operated in the ‘Linear-Sweep’ frequency mode, while the oscilloscope is operated to record the input and output of the test system in the ‘Envelope or Peak Detector’ acquisition mode. Under these conditions, the acquired envelopes correspond to the spectra, whose ratio yields the amplitude frequency response. The method can be easily configured and does not require external control or programming. Details of its implementation along with transfer function measurements on a model coil and an actual transformer are presented.