Some multimeters have a pretty high open circuit voltage in continuity test mode and resistance mode (possibly to improve SNR?), but they are current limited. For example, the Fluke 87V behave like an 1mA constant current source with a maximum output voltage of ~7.3V in continuity mode.

I think it is generally safe to use these multimeters to probe ICs, as most of them have clamping diodes. The question is, will capacitors with a low voltage rating be damaged (with a low limited current)? This is a common scenario when I probe power rails on a board to test for short circuits:


simulate this circuit – Schematic created using CircuitLab


1 Answer 1


Continuity or Resistance mode applies a very low constant current such as 1mA to 1uA so no such damage will occur at low voltage. There is not enough power.

However, I suspect leaving a reverse voltage charge on a supercap over time will degrade the capacitor just like leaving a battery undercharged that is not a "deep-state discharge type" will oxidize and damage battery performance over time. (hours)

Therefore if you do test reverse resistance , that's ok for the short term but do not leave a negative voltage on the cap. So you can expect dV/dt=Ic/C so if 1 Farad and 1mA you expect 1mV per second change in voltage. Use Voltage mode to check voltage after resistance test shows 0 Ohms

Note: R or diode test mode on a DMM = +ve V on +red
and on an Analog meter in Resistance mode, the voltage applied is the reverse (+ve V on -ve black) and displayed voltage is shown in R with a log graticule on meter.

WIKI REF However reverse-charging a supercapacitor lowers its capacity, so it is recommended practice to maintain the polarity resulting from the formation of the electrodes during production.

  • \$\begingroup\$ I wonder if a few hundred microamps might still be enough to damage supercapacitors, which tend to be fairly sensitive devices. \$\endgroup\$
    – Hearth
    Dec 12, 2019 at 15:06
  • 2
    \$\begingroup\$ @Hearth It may rise a few negative uV or mV , but should be negligible aging. But if -10% of forward rated voltage, that could be significant degradation. \$\endgroup\$ Dec 12, 2019 at 18:05

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