Hello all,
Properly a rookie question, but i am confused!, just got my Rigol1054Z scope, and i am experimenting with a mix of ac and dc signals.
When i use the scope to measure a dc voltage, on ea channel 1, i adjust sensitivity to 1volt/div and then on the left side of the screen, i choose measurement (from the row of bottums on the left side of the screen) to show me RMS voltage fron channel 1 in the little displays on the lower side of the screen. If i connect my channel probe directly to my dc power supply, and adjust to, lets say, 3 volt, and double check with my digital voltmeter, i always have a little higher voltage on the scope, compared to the DVM. Then, i disconnect the scope probe completely from the scope, and change input on channel 1 from DC, to GND. This should internally connect input on channel 1, to GND right?. the strange thing is that RMS measurement, on the little display reading on the scope do not drop to 0,00 volt as it should, it only drops to around 30 mV and freeze, sometimes even only around 60 mV, but not 0 volt. In other words,
If i just disconnect the propes, a small voltage og around 30-40 mV is shown in the Rms reading, and also if i reconnect the probe and zero it by connecting GND to the hot tip of the probe.
It is like i always will have a small DC voltage offset on my inputs even if they are fully grounded, is that really correct, can i somehow compensate for this? I have tried the scope calibration in the utility menu, but it did not help.
I have read somewhere to use Per.Vrms instead, but this measurement seems not to be able to measure DC.
It seems soooo complicated to measure a simple DC value correct on this scope, can that be right, why can i not "zero" my RMS reading?
br
Martin / denmark