4.5 Control Loop Gain and Phase Measurement Procedure
Connect 1 kHz to 1 MHz isolation transformer to TP6 and TP8 as show in Figure 4-3.
Connect input signal amplitude measurement probe (Channel A) to TP8 as shown in Figure 4-3.
Connect output signal amplitude measurement probe (Channel B) to TP6 as shown in Figure 4-3.
Connect ground lead of Channel A and Channel B to TP5 & TP7 as shown in Figure 4-3.
Inject 30 mV or less signal across R1 through isolation transformer.
Sweep frequency from 1 kHz to 1 MHz with 10 Hz or lower post filter.
Control loop gain can be measured by:
Control loop phase is measured by the phase difference between Channel A and Channel B.
Control loop for Channel 2 can be measured by making the following substitutions.
Change TP6 to TP16
Change TP8 to TP14
Change TP5 to TP17
Change TP7 to TP15
Disconnect isolation transformer before making any other measurements (signal injection into feedback may interfere with accuracy of other measurements).