Refering to the attached graphic:
Two NI PXI-4071s measure the same ramping stimulus voltage one sample at a time as both 4071s cycle through 3.5, 4.5, 5.5, 6.5 and then 7.5 digit-resolution settings. The graph labeled “dV Waveform Chart” displays an acquired-PXI-4071-Refference voltage subtracted from an acquired-PXI-4071-DUT Voltage as the (Blue) center trace along with the (White) maximum-tolerance-limit above and the (Red) minimum tolerance-limit below. The graph labeled “V Waveform Chart” displays the (Red) inverted-PXI-4071-Refference-Range, (White) noninverted-PXI-4071-DUT-Range and (Blue) applied-stimulus-ramp-voltage. There is a peculiar oscillation displayed on the “dV Waveform Chart” that occurs only during 6.5 digit resolution on 0.1V, 1V, 10V, 100V & 1000V range acquisitions and becomes less significant at the higher ranges. Changing the internal-zeroing and/or internal-calibration settings changes the oscillation offset and/or frequency but not the peak-to-peak amplitude. What is this oscillation and how can it be eliminated? As can be seen, there is less noise at 5.5 digit-resolution than at 6.5 digit-resolution.
Two NI PXI-4071s measure the same ramping stimulus voltage one sample at a time as both 4071s cycle through 3.5, 4.5, 5.5, 6.5 and then 7.5 digit-resolution settings. The graph labeled “dV Waveform Chart” displays an acquired-PXI-4071-Refference voltage subtracted from an acquired-PXI-4071-DUT Voltage as the (Blue) center trace along with the (White) maximum-tolerance-limit above and the (Red) minimum tolerance-limit below. The graph labeled “V Waveform Chart” displays the (Red) inverted-PXI-4071-Refference-Range, (White) noninverted-PXI-4071-DUT-Range and (Blue) applied-stimulus-ramp-voltage. There is a peculiar oscillation displayed on the “dV Waveform Chart” that occurs only during 6.5 digit resolution on 0.1V, 1V, 10V, 100V & 1000V range acquisitions and becomes less significant at the higher ranges. Changing the internal-zeroing and/or internal-calibration settings changes the oscillation offset and/or frequency but not the peak-to-peak amplitude. What is this oscillation and how can it be eliminated? As can be seen, there is less noise at 5.5 digit-resolution than at 6.5 digit-resolution.
