F4.2 Functional Testing M8SL2-00-002-812
© Copyright Tait Electronics Limited August 2004. All rights reserved.
4.3 Output Noise
To check that output noise is within specification, proceed as follows.
• Ensure that the main supply to the T800-23-0011 is switched off. Set up the
test equipment as shown in Figure 4.1. Connect the T800-23-0011 to the
mains supply and switch it on.
• 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 less than 100mV
pp
under all load and line condi-
tions.
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.
4.4 Overall Power Supply Stability
To check for overall PSU stability, proceed as follows.
• Ensure that the main supply to the T800-23-0011 is switched off. Set up the
test equipment as shown in Figure 4.1. Connect the T800-23-0011 to the
mains supply and switch it on.
• 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.
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