Measuring the Disspation of the self capacitance of a thru hole resistor. (2023 Update)

If your self capacitance is in parallel with the resistor, then the dissipative resistance of that capacitance is in series with the capacitance. Depending on the frequency, the dissipative resistance will have a different impact on your circuit. Are you taking this into account with your math? Or are you treating the dissipative resistance as being in parallel with the actual resistance? I've never done the math, but the two circuits may be equivalent with different values of the dissipative resistance.

I guess my point is that it would seem that the parasitic capacitance would have to have a rather low impedance at your test frequency to have this effect on the circuit. What frequency are you testing?

If that is true then I did the calculations wrong. Unless the series resistance is over 9.34MΩ, it doesn't explain the 10MΩ measurement error. Rethinking, maybe the resistors self capacitance is much higher than 22 and it could work out to 9.34MΩ.

I have only tested at 1MHz. Remember, I'm trying to measure the value of a 10MΩ resistor on a Q meter and got 4,280,000Ω instead of 10MΩ, I'm trying to make sense of the answer I got.

Yes, that is what I'm doing

Or, the answer could come out right if a higher Q is used, 22 is very low for a capacitor, but it's not a designed capacitor, it is a stray capacitor.

Testing at 1MHz and the parasitic capacitance measures at 0.37pf. Thanks, Mikek

OK, time for my theory, feel free to tell me if it is not good. Since the 0.37pf is being resonated, its R is magnified by Q of the capacitor. So, I get a large R in parallel with my 10MΩ, lowering the total R. Here is a drawing showing the details as I see them.

It sounds like you're operating outside of your test equipment's rated tolerances.

RL

Looking in the manual it shows 1000MΩ can be measured at 50kHz and over 900MΩ at 1MHz. I'm measuring at 1MHz. I can clearly define the change in capacitance when I add the resistor. So I don't see a problem there. I will note, since the previous 1/2W 10MΩ, I have measured a 10MΩ 0805 smd resistor and I have closer answers of 7MΩ to 9.2MΩ, dependent on how the resistor is mounted. The surface mount resistor measures 0.12pf to 0.14pf, well, 0.3pf with the apparently bad mounting that I thought would be good. But it still gave me an almost 8MΩ measurement. I am out of the range the injection voltage the internal meter will read, so I have an external meter measuring the lower injection voltage, (a well known practice.)

I hate to harp, but I'm looking to understand, does resonance of the resistors self capacitance result in a large parallel R? Here is a drawing showing the details as I see them.