4.4 Control Loop Gain and Phase Measurement
Procedure
Connect a 1-kHz to 1-MHz
isolation transformer to TP2 and TP3 as shown in Figure 4-1.
Connect an input signal amplitude
measurement probe (Channel A) to TP2 as shown in Figure 4-1.
Connect an output signal
amplitude measurement probe (Channel B) to TP3 as shown in Figure 4-1.
Connect the ground lead of
Channel A and Channel B to TP 4 as shown in Figure 4-1.
Inject 25-mV or less signal
across R7 through an 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.
Disconnect the isolation
transformer from TP2 and TP3 before making other measurements (signal injection
into feedback can interfere with accuracy of other measurements).