Newtons4th PSM3750 NumetriQ, Startup Manual, Page: 41 / 104

PSM3750 Quick User Guide
Page 39
From the RMS Voltmeter display screen we can see the 2 sets of measurements
from the same input. CH1 is displaying both the ac+dc components of the input
signal with the ranging set onto the 10V scale.
CH2 which is set to ac only displays the rms ac measurement from the 100mV
input whilst ignoring the 5V dc offset with the autoranging now set onto the
300mV range.
Accuracy for the RMS mode =
0.075% range + 0.075% r 0.05mV <10 kHz
So the greater accuracy is achieved on CH2 by extracting the dc component of
the signal through enabling a smaller range to be used.
Viewing both channels within the Oscilloscope mode it is clear that by setting the
coupling to ac only, the same ac waveform is much more visible with
in CH2’s
screenshot.