I was just playing with a new multimeter (KaiWeets HT118E) when I was curious about the voltage it uses when measuring capacitance.

I hooked up my scope to the DVM in capacitance mode and saw a triangle wav at around 22KHz, this is an AC signal, it crosses the 0volts line.

This means that for brief intervals the capacitor is being subject to the wrong polarity, when I put a 0.1 uF capacitor across the leads the frequency drops right down to some 50Hz or so, but the AC is till there, the capacitor is wrongly "biased" for about 50% of the time, the peak voltage of the triangle wave is just over 1v.

I know the voltage is small, but surely a well designed capacitance meter should be sensitive to the fact that one might be testing an electrolytic...

 

A standard electrolytic can tolerate 1-1.5V in the reverse direction without damage, so maybe that is what they assumed when designing the meter to measure capacitance.

 

My DMM has polarity markings on the capacitance inputs.
I will test with the oscilloscope and report back.

 

This is what I see, a digital unipolar signal, 0 to 3 V, 2.5 Hz.