I have a Tektronix P6245 active probe (allows only DC input) and wish to use it to see noise on various power supply rails. I've done this already on a +3.3V rail, and can get sufficient DC offset on the scope (Tek TDS744a) to see millivolts.
However, it gets tricky with higher voltages (within the probe limits). For example, a +12V DC rail is tough. Bringing the vertical resolution to a level that will provide meaningful data is simply not possible.
I'm considering a dc blocking capacitor between the probe and the rail under test. Is this a reasonable option? Any suggestions for best way to do this?