Capacitor resistance

Thread Starter

Simon Pressure Jet

Joined Oct 28, 2020
13
Hi. Can someone explain to me how the resistance of a capacitor increases as it charges?
I have a 4.5 microfarad capacitor in my hand. When I put my multimeter to ohms and connect the leads to the discharged capacitor terminals I notice the resistance steadily increases until the capacitor is charged but I don‘t know why. Please can someone explain this to me.

Many thanks Simon.
 

AlbertHall

Joined Jun 4, 2014
11,506
In this case your meter isn't reading the 'resistance' of the capacitor.
The meter measures resistance by sending a current out of the probes and measuring the voltage this current produces across the connected component. When the component is a capacitor this current charges the capacitor and so as the voltage across the capacitor rises, the meter interprets this as being an increased resistance.
 

centuryold

Joined Nov 26, 2020
1
In this case your meter isn't reading the 'resistance' of the capacitor.
The meter measures resistance by sending a current out of the probes and measuring the voltage this current produces across the connected component. When the component is a capacitor this current charges the capacitor and so as the voltage across the capacitor rises, the meter interprets this as being an increased resistance.
THanks albert for the proper explanation.
 

Thread Starter

Simon Pressure Jet

Joined Oct 28, 2020
13
Hi. Thanks for the explanation. I understand how the multimeter is reading resistance as the capacitor charges now and how when charged the resistance is infinity, or on my multimeter “OL”.
 

MrChips

Joined Oct 2, 2009
24,240
I often use an analog ohmmeter to judge capacitance.

Low capacitance (<1μF) would show infinite resistance.
Higher value capacitance would cause the meter needle to kick to a low resistance value and then gradually rise.

The time response of the kick, the rate of increase, and where it settled would be an indication of the capacitance value and leakage.

This often tells me quickly if the capacitor needs replacing. A bad capacitor shows up as a short, as open (no kick), or high leakage (finite resting resistance).
 

AlbertHall

Joined Jun 4, 2014
11,506
I often use an analog ohmmeter to judge capacitance.

Low capacitance (<1μF) would show infinite resistance.
Higher value capacitance would cause the meter needle to kick to a low resistance value and then gradually rise.

The time response of the kick, the rate of increase, and where it settled would be an indication of the capacitance value and leakage.

This often tells me quickly if the capacitor needs replacing. A bad capacitor shows up as a short, as open (no kick), or high leakage (finite resting resistance).
And this doesn't work nearly so clearly with a digital meter.
 
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