Electronic – Orientation of “bipolar” capacitors on PCB


I've come across a video on a popular and well-respected electronics channel on Youtube where they say that even bipolar capacitors have a preferred orientation in a circuit that minimizes hum and interference etc.
They describe an oscilloscope based method to determine that orientation of the capacitor that is easy enough to implement.

I wonder, however, once that capacitor polarity is determined, how to find out which way to put the cap into the PCB .. without knowing too much about the circuit or the schematics. Is there a multimeter or oscilloscope based measurement that could be carried out? The capacitor is supposed to go into the board so that one side goes in direction of lower impedance and the other in direction of higher impedance. Positions of electrolytic caps are labeled + and -, but PCBs are not typically labeled that way for bipolar caps, and schematics of circuits are not always available.

I understand that most people would consider this overkill on most circuits, but I'm interested if it's technically possible to carry out the corresponding measurement on the PCB side of things. Thanks!

Best Answer

If you have a capacitance meter, you can wrap the capacitor in aluminum foil and measure the capacitance between each lead and the foil. The lead connected to the outer wrapper (or can) will have a slightly higher capacitance; you may be able to detect this. If your capacitance meter has a 'guard' terminal, connect this to the unused capacitor lead -- this will create a more significant change between measurements of each lead.

Note the capacitance you may measure will be quite small -- few pF, and you will need a stable and repeatable setup.