Noise and Ripple measurement

One common use for wirewound resistors seems to be as the load for a converter. I also use that configuration when doing thermals to simulate the customer s system and for noise and ripple measurements. But rarely do I use it for anything else. I would strongly suggest you get yourself a good electronic load. But do remember to set it to CC mode (constant current mode). Because a resistor (or an electronic load set to CR mode) is just too benign. For example, rarely does it reveal any fundamental start-up issues. 

Recommendation 2 (Figure 6-9) As previously discussed, a small ceramic capacitor of about 0.1 pF is recommended at the output, for carrying out more meaningful noise and ripple measurements. That measurement is tricky and we must do our best to avoid any pickup by removing the ground lead of the probe. The scope probe must be used correctly as shown. Also disconnect all other scope probes completely from the board during this measurement. 

Figure 11-1 One Possible Way of Conducting a Noise and Ripple Measurement for an AC-DC Power Supply... 

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