DER-120
Triple Output Flyback – DPA424R
October 26, 2005
10.4 Output Ripple Measurements
10.4.1 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 15 and Figure 16.
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 15 – Oscilloscope Probe Prepared for Ripple Measurement. (End Cap and Ground Lead Removed)
Figure 16 – Oscilloscope Probe with Probe Master 5125BA BNC Adapter. (Modified with wires for probe ground for
ripple measurement, and two parallel decoupling capacitors added)
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