3: Setting up PMUs and PGUs in Clarius Model 4200A-SCS Pulse Card (PGU and PMU)
3-36 4200A-PMU-900-01 Rev. B March 2023
The equation shows that this effect is a function of the capacitance, as well as the dV/dt. Therefore,
minimizing the capacitance will reduce this measurement artifact. The cabling is typically the largest
contributor to the system capacitance. Slowing down the pulse transitions will also reduce the height
of the current charging effect.
This capacitive charging current is primarily a measurement artifact, as the current does not flow
through the DUT. Note that if a spot mean is taken during the settled portion of the pulse, then this
charging does affect the spot mean measurement.
The following two figures show the waveforms and setup for a pulse test on a resistor DUT and
illustrates a configuration to eliminate this artifact. The following figure shows that the channel 2
current waveform does not have this current charging artifact. This is because channel 2 is not
pulsing, so dV/dt = 0. Using channel 2 in this configuration is sometimes called "low-side
measurement." This measurement approach is useful when analysis of the current signal pulse
transitions is required.
Figure 66: Low-side measurement waveforms
The previous figure shows the current waveforms for both PMU channel 1 (high side) and channel 2
(low side) current measurements. Note that channel 2 does not show the capacitive charging effects.
Also, note that the channel 2 current measurement is negative because the current is flowing into
channel 2.
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