Totally new to oscilloscopes, my 2204A is to be delivered in a few days.
My initial interest is measuring AC RMS voltage and frequency on the speaker level outputs of an OEM car audio head unit, rated at about 30 Watts RMS. Measurements will be taken at various volume settings using a range of sine wave test tones between 20Hz and 20kHz (test tones are wav files on a USB stick which will be played through the head unit using its USB input port).
Based on the rated head unit output I anticipate the signal to be measured will range from 0VAC RMS to about 15-20VAC RMS, 20Hz to 20kHz. The object of the exercise is to look for 'clipping' and note the frequency/volume (voltage) conditions where that arises. Voltage data will be entered in a spreadsheet which will generate EQ curves at various frequencies.
Wanting to avoid any novice pitfalls, I am trying to understand proper connection of the 2204A passive probe ground for this application....
1. When both the car system and the laptop computer are running on their respective internal battery power, should the probe ground be connected to the (-) terminal of the speaker output of interest, or to the head unit chassis ground?
2. If using both probes to simultaneously measure two different output channels, should both probes be 'grounded' or only one?
3. If I connect the car battery to a charger plugged-into "mains power" while conducting the measurements, does this change how I should connect the probe ground? What about if the laptop is connected to "mains power" via its charger block while conducting the measurements?
Thanks in advance for any education provided.