Take this image of a waveform with DC offset taken with PCLab2000SE:
The dV is 3.88V, and measured Vrms is 1.39V. That is obviously wrong. 1.39V is what it would be without DC offset:
Amplitude = 3.88 / 2 = 1.94V
1.94 / 0.71 = 1.37VI confirmed it with a function generator. Adding DC bias doesn’t change Vrms.
Is this something that can be fixed in the software?
I’m sorry for the inconvenience.
If you select Help -> Contents -> Menu Options -> View Menu
There is written:
“RMS Value
Displays AC RMS value of the signal”
If you click the “RMS Value” there is written:
“RMS Calculation
When this option is selected the true RMS AC value of the signal is displayed on the screen”
To avoid confusion there should be written on the screen “AC Vrms”…
Wouldn’t it make more sense to show the Vrms + bias in DC mode?
[quote]Wouldn’t it make more sense to show the Vrms + bias in DC mode?[/quote]Indeed, this may have been an option but may have been also confusing for some users…
Now the PCS100 is working as most DMMs: Measuring the ac-coupled true-rms signal, rejecting the dc component, if any is present.
BTW: Oscilloscopes such as PCS500, PCSU1000, PCSGU250, PCSU200 and EDU09 have Waveform Parameters display option to measure AC RMS and AC+DC RMS.