Lets say you have a flyback with a 20V dc input and 2 secondary side outputs, 5V and 12V. The 20V power in is provided by a benchtop power supply. What is the safe way to measure the input and output sides of the converter?
Can you connect to the secondary side rails using a single ended probe only or would this cause ground loops through the bench equipment? Can you connect primary using a single ended probe and secondary using a differential probe using the same oscilloscope?
If you have access to a decent 4-channel Oscilloscope you can use a single-ended probe on each of +Vin, -Vin, +Vout, -Vout. (You can leave the gnd clips for each probe unconnected.)
Use your oscilloscope math function to subtract (+Vin - -Vin) to measure the input voltage and do likewise to measure the output voltage (+Vout - -Vout). In this way you are measuring all signals with respect to a somewhat arbitrary GND reference, but the point is it is the same reference point and therefore is canceled out by subtraction.
