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B5.4
T807/808 Functional Testing
M800-00
31/08/96
Copyright TEL
5.3
Output Noise
Set up the test equipment (except PS1 & PS2) as shown in Figure 4.1.
Connect a digital voltmeter (e.g. Fluke 77) across the load terminals and set the
meter to its lowest AC volts range.
Check that the reading is <10mV AC for both the T807 and T808 under all load
and line conditions.
Note:
A
real
reading of the level of noise present on the output of a switching
power supply is very difficult to obtain, as low noise levels, common mode
noise paths and ground loops all lead to inaccurate measurement results.
The procedure outlined above will, however, give a good indication of the
output noise.
5.4
Overall Power Supply Stability
Connect the oscilloscope across the output.
Vary the mains voltage and DC load over the full specified range (refer to Section
1.2).
Check on the oscilloscope that no oscillations occur.
Check that no audible noise can be detected, except with open and/or short cir-
cuit loading on the output.
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