Pearson PRD-120

Description 

The Pearson PRD-120 facilitates the measurement of power line ac ripple using a frequency-selective voltmeter, i.e., EMI receiver or spectrum analyzer. In so doing, it greatly simplifies both the manual and automated measurement of injected ripple in such standards as MIL-STD-461 CS01/CS101, RTCA/DO-160 section 18 and MIL-HDBK-704-2 through -6.

The PRD-120 is a passive signal conditioner, providing dc blocking, selectable ac attenuation, and transformer isolation to allow connection of a sensitive frequency selective voltmeter across the power bus in lieu of the traditional oscilloscope. See Figures 2a and b. Note that in Figure 2b, the spectrum analyzer/EMI receiver is not powered through an isolation transformer, because the required isolation is built into the PRD-120. The spectrum analyzer/EMI receiver operates with safety ground intact, while maintaining the isolation of the test sample power return above ground. Another difference between the Figure 2a and b drawings is that the PRD-120 connects across the test sample, as required in Figure 2a, and also across the power source. This added feature provides greater test control. By inspection, ripple injected by the coupling transformer must drop either across the test sample (desired), or across the power source (undesired).