After reading my article about finding out capacitor inner-outer foil, some of my readers asked me to do the similar test on the resistor. Well, technically speaker, resistor shouldn’t have any inner or outer foil, since most likely it’s a piece of carbon or wire on the ceramic core. But let’s see the testing result. On this simple session, I used Kiwame (Carbon Film Resistor) and Mills (Wirewound). I also have some Riken or Shinkoh, but not really available in many values. For Kiwame, I used 1M, 470K, 100K, and 2K2. For Mills, I picked one value, 22K.
1 MegaOhm readings below showed 332 mV.
If I reversed the orientation, it read 248 mV.
470 KOhm readings was 200 mV.
If I reversed it, we got 132 mV.
Getting lower, I tried 100 KOhm. We got around 59 mV.
If I reversed it, we got around 52 mV.
I went even lower to 22 KOhm with Mills. I got 57 mV readings.
Again, let’s switched the orientation and we got 52 mV readings.
Now we went even lower to 2K2 Ohm, back to Kiwame again. The first readings showed 7.4 mV.
If I reversed it, I got 7 mV.
Some conclusion from my own is:
- I rarely see any resistor marks the in and out orientation.
- The larger the resistance (for the same resistor) the larger also the different between one side and the other (on 1 MegaOhm resistor, the different was between 332 vs 248 mV, while on the 100 KOhm resistor, we got 59 vs 52 mV only).
- Just like the capacitor, different type (structure, design, material, etc) may have different noise level (as you can see on the test above, 100 KOhm Kiwame has similar noise with 22 KOhm Mills, one was Carbon Film while the other was Wirewound).
- Can I ignore those resistors orientation? For most value, around 100 KOhm, I think the different is so small to be noticed. But if you are a perfectionist, you better measure it one by one – at your own pain of course 😉
Here is some of my collections used for the testing purpose.