Figure 5-4 shows the test setup for the amplifier transfer function measurement. The output of the amplifier is differential which is unique to measure. For this reason, the amplifier input connects to the signal source through an isolation transformer (Figure 5-5). This self-made isolation transformer has flat frequency response in the band of interest (Figure 5-6, Table 5-2). For this frequency range, an oscilloscope with the built-in bode-plot function serves the purpose very well.

Figure 5-4 Test Setup for the Transfer Function Measurement

Figure 5-5 Self-Made Isolation Transformer

Figure 5-6 Isolation Transformer Transfer Function (High-z Loading)

Figure 5-7 and Figure 5-8 show the transfer function of the excitation amplifier. Note the loading effect of the resolver in Figure 5-8. In the low frequency range up to about 3kHz there is noticeable gain drop. Nevertheless, for the frequency band of interest, between 5 to 10kHz, the transfer function remains constant.

Figure 5-7 Amplifier Transfer Function (Unloaded Output)

Figure 5-8 Amplifier Transfer Function (Resolver as a Load)