Testing capacitors

[cider]

Hi. I need to test a capacitor. Am i correct in thinking they are to be discharged first by shorting the terminals ? also am i correct in thinking i use the F setting on my multi meter which goes from 2n to 200n and then 2u to 200u as per cap rating ?

Many thanks

also cap should be within 10% ?

 

[ricicle]

You need to set the meter to the range that includes the rating of the capacitor. You will also need the leads in the correct sockets (if applicable) and the polarity correct if the capacitor is polarised.

 

[Monkeh]

Am i correct in thinking they are to be discharged first by shorting the terminals ?

Probably wise, unless the cap is large or rated for several hundred volts, in which case you'll be requiring new underwear. You'd want to use a resistor in that case.

also am i correct in thinking i use the F setting on my multi meter which goes from 2n to 200n and then 2u to 200u as per cap rating ?

Whichever one of these settings is appropriate for the size of capacitor, yes..

also cap should be within 10% ?

Is the cap specified for 10% tolerance? What's the accuracy of the meter? You'll know if it's bad (well, okay, maybe not, you can't test ESR), otherwise don't worry yourself over specifics.

and the polarity correct if the capacitor is polarised.

No, actually, that doesn't matter for this.

 

[flameport]

What is this capacitor actually for?
If it's already suspect and is the only one (such as for a motor etc.), it will be far easier to just buy a new one.

A multimeter with capacitance range can be used as suggested, but this won't really tell you anything about the condition of the capacitor.

 

[Monkeh]

A multimeter with capacitance range can be used as suggested, but this won't really tell you anything about the condition of the capacitor.

Well, they can, but it depends on the type of capacitor and what specific characteristic they were employing it for.

 

[plugwash]

Probably wise, unless the cap is large and rated for several hundred volts,

Even a low voltage capacitor can be quite violent when shorted if it's big enough.

 

[Monkeh]

Yes, typo fixed.. Don't need a video to know how caps behave, thank you.

 

[Spark123]

To the OP, what is the problem with the capacitor?
A test using a multimeter may tell you the capacitance of it but will not tell you if it is breaking down under voltage.

 

[Agile]

That's quite true but as with most things in the world it helps to have an idea of what you want to find out first.

A meter will measure the capacitance which is very useful for motor start/run capacitors.

Measuring other parameters needs more specialised equipment.

Tony