Measuring Capacitors

[FloorIt]

Just received an order of components from Mammoth. I'm going through and measuring all of the resistors and capacitors. All of the resistors measure ok and several of the caps do as well. Two polyfilm and one ceramic cap are not giving me the proper values. Here is what I have:

473J: should be 0.047 uF but reads .061 uF

103J: should be 0.01 uF but reads 0.022 uF

471J: should be 470 pF but reads 12 nF

I don't have experience measuring caps. Any technique I need to be aware of?

[copachino]

Just received an order of components from Mammoth. I'm going through and measuring all of the resistors and capacitors. All of the resistors measure ok and several of the caps do as well. Two polyfilm and one ceramic cap are not giving me the proper values. Here is what I have:

473J: should be 0.047 uF but reads .061 uF

103J: should be 0.01 uF but reads 0.022 uF

471J: should be 470 pF but reads 12 nF

I don't have experience measuring caps. Any technique I need to be aware of?

There its not science on that, but you reading are affected by... tolerance of capacitor, and tolerance of you instrument... adding that you will have a chance of error.. i have never and i mean never see a cap that has the exact value of what its marked... even if the cap its ok you measssuring instrument will lie to you a bit.

[blearyeyes]

20% tolerance with caps...

[miter53]

Using long leads affects the measurement. The capacitance meter I use (Tenma) comes with 6" long leads and has a zero adjustment to compensate for the lead capacitance. It also has a socket to eliminate the leads entirely.

[Rockhorst]

Measuring caps is much more finicky than resistors. My DMM has a cap setting, but usually it shows the right value for about a second and then ramps up. Getting a stable reading is difficult.

[GermanCdn]

Using long leads affects the measurement. The capacitance meter I use (Tenma) comes with 6" long leads and has a zero adjustment to compensate for the lead capacitance. It also has a socket to eliminate the leads entirely.

This.  If you have leads of any sort on your DMM, you won't get an accurate reading on anything below 1 nF, so pF caps are generally out of the question.  That being said, it looks like you have a couple of caps that are way out of spec.

[pickdropper]

Using long leads affects the measurement. The capacitance meter I use (Tenma) comes with 6" long leads and has a zero adjustment to compensate for the lead capacitance. It also has a socket to eliminate the leads entirely.

This.  If you have leads of any sort on your DMM, you won't get an accurate reading on anything below 1 nF, so pF caps are generally out of the question.  That being said, it looks like you have a couple of caps that are way out of spec.

Yep, I have a fairly nice Fluke, and it is only spec'd down to 1nF, even though it does have a relative setting to zero out the capacitance of the test leads.