Ampro AM-510 owners, Please help, how to measure uF?

[Ampro510]

Hello everyone,

I've got an Ampro AM-510 multimeter, and this is the first multimeter I've ever owned. It seems like a decent inexpensive multimeter, but their owner's manual isn't very informative IMO.

I've got a LCD TV here from which I've taken some capacitors out of circuit, and I would like to test the uF reading on each one to see if they should be replaced.

So here's my problem:
I turn the dial on my AM-510 to capacitance mode, and it automatically starts out in nF (I want uF). I know this is an autoranging meter, so I assumed it would work it's way up to uF as it took the reading.

When taking the reading it mostly stays in nF, and randomly switches to uF for a moment, then immediately back to nF. I have read through the manual and I can't seem to figure out what is going on and why I'm unable to get a reading in uF. This meter is rated to read up to 100 uf, so it should be capable of doing what I need, but it's so confusing how it keeps alternating between measurements.

If anyone could please help me I would be very appreciative! I have emailed customer support, but so far no answer. I also have done a couple searches on these forums but to no avail. Thank you all in advance!!! 

[Vito_R]

What are the values of the caps you're testing?  Make sure you discharge them before you try to test them or it will damage your meter and give erratic readings like that.  Is your meter simply at the end of the nF range and that's the reason it's switching back and forth between nf / uf ranges?  Check the range specs in the manual.

[Ampro510]

What are the values of the caps you're testing?  Make sure you discharge them before you try to test them or it will damage your meter and give erratic readings like that.  Is your meter simply at the end of the nF range and that's the reason it's switching back and forth between nf / uf ranges?  Check the range specs in the manual.

Thank you very much for your response!

I am testing capacitors that are rated 1000uF, 25V.

I discharged the capacitors prior to testing them, based off of various advice I read from the internet, I used a large flathead screwdriver with a plastic handle to touch both legs of each capacitor. Is this an acceptable method to discharge capacitors?

That's a good question, and I did as you said and checked the range specs in the manual. The AM-510 has a range up to 400nF, and up to 100uF.

My meter reads a constant 12.58nF when not being used to test anything. I do have a relative zero feature on this meter, and have tried testing both with and without the relative zero turned on.

When tested the aforementioned capacitors, I get readings everywhere between 40nF to 47uF, and the reading goes up & down all over the place and switches between nF and uF. Does this sound normal, or might I have a faulty multimeter?

Thank you very much!

[Vito_R]

Best way to discharge caps is with a resistor installed on insulated alligator clips like a 100ohm 10 watt.  If you're trying to test a 1000uf cap and you said your meter only goes to 100uf then it would be out of range.  If not then maybe your meter is defective.

[Vito_R]

Just checked your manual and it does say max range on capacitance is 100uf.  If you're testing a 1000uf cap it will not work.  You need another meter.  Try picking up a cap meter that also tests ESR.

[rob77]

that 12.58 nF without connected to anything is suspicious... try to measure a known capacity which is withing the range of the meter to verify the meter itself.

[Ampro510]

doh! I don't know how I missed that, you are absolutely correct Vito_R, thank you for pointing that out! Looks like I'll need to shell out some more cash on another meter!

And I will take your advice on the insulated alligator clips + resistor to discharge capacitors, thank you for that!

Thanks for the recommendation rob77, I will investigate further into this.

You guys are great, and very much appreciated!