EPR-29 – 4 Output, 11 W, Universal Input, DVD Supply
07-July-03
11.5 Output Ripple Measurements
11.5.1 Ripple Measurement Technique
For DC output ripple measurements, a modified oscilloscope test probe must be utilized
in order to reduce spurious signals due to pickup. Details of the probe modification are
provided in Figure 28 and Figure 29.
The 5125BA probe adapter is affixed with two capacitors tied in parallel across the probe
tip. The capacitors include one (1) 0.1 µF/50 V ceramic type and one (1) 1.0 µF/50 V
aluminum electrolytic. The aluminum electrolytic type capacitor is polarized, so proper
polarity across DC outputs must be maintained (see below).
Probe
Ground
Probe Tip
Figure 28 - Oscilloscope Probe Prepared for Ripple Measurement (end cap and ground lead removed).
Figure 29 - Oscilloscope Probe with Probe Master 5125BA BNC Adapter (Modified with wires for probe
ground for ripple measurement and two parallel decoupling capacitors added).
Power Integrations, Inc.
Tel: +1 408 414 9200 Fax: +1 408 414 9201
www.powerint.com
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