Whats a good multi meter for small voltage?

[The motor guy]

Still trying to test my alternator for ac noise, but it seems my fluke meter isn't good enough. 100mv is the least amount it will measure and ac noise for an alternator isn't suppose to be more than 50mv.

 

[JavierH19]

That's a tough one, if a fluke doesn't do it not much else will. I'd hop on an enthusiast electronics forum for that one.

 

[twX]

You'll probably need an oscilloscope. You can find some basic ones on Amazon for under $50 that should work well enough for measuring a 50 mV ripple.

 

[The motor guy]

That's a tough one, if a fluke doesn't do it not much else will. I'd hop on an enthusiast electronics forum for that one.

I did that and they closed the question and said consult an electrician. lmao One guy did say a fluke multi meter 117 would measure less than .05

 

[supton]

How much can we spend for you?

DM600 Compact Digital Multimeter

Amazing deals on this Dm600 Compact Digital Multmeter at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

auto-ranging, looks like it has a 2V range, so it should get well below 0.1V.

Some of the cheaper HF ones indicate but one AC voltage range, which would mirror the Fluke FL-323 that you have (and are finding insufficient).

 

[sloinker]

Throw a capacitor/condensor on it and forget the measly millivolt readings you are looking for.

 

[supton]

I'm a bit dubious of this one:

DM300 Pocket Sized Digital Multimeter

Amazing deals on this Dm300 Pocket Sized Digital Multimeter at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

but it too has multiple AC ranges, and its price is a third of that first option.

 

[supton]

Throw a capacitor/condensor on it and forget the measly millivolt readings you are looking for.

You could do that, but you'd want to know the frequency and amplitude of the voltage signal, then you could size the capacitor value and ESR. Although knowing what the alternator output impedance would come into play at some point... I guess you could count on the distance from alternator to capacitor, it's what, 4nH per inch? times 2 for return path?

Of course, a good battery is one heck of a capacitor, lots of Farads and a pretty low ESR at that (until it's bad of course). But your alternator has to feed it first, then the rest of the car, otherwise its filtering ability is not so good. Not sure how most cars wiring is done, would hope it's star configuration off the battery and not star off the fuse box.

But I think the OP is hoping to look for a bad rectifier, want to say, his model is known for that, which may take out the ECU when it acts up? something like that.

But yeah, I'd toss a scope at it myself. They have some dirt cheap single channel scope kits on Ebay that I'd consider good enough here.

Fun little kit to put together, I bought one just because I could... one 5V USB battery pack to power it and it's a nice portable unit (that's just about useless to me for anything other than stuff like this).

 

[Chris142]

If you take the car to any auto parts store they can test the system for ripple.

 

[The motor guy]

If you take the car to any auto parts store they can test the system for ripple.

Do you take the alternator off to do the test?

 

[The motor guy]

I did that and they closed the question and said consult an electrician. lmao One guy did say a fluke multi meter 117 would measure less than .05

It was an electricians forum and my username was The hobbyist. I guess that's what I get. lol

 

[Chris142]

Do you take the alternator off to do the test?

No

 

[4329]

Still trying to test my alternator for ac noise, but it seems my fluke meter isn't good enough. 100mv is the least amount it will measure and ac noise for an alternator isn't suppose to be more than 50mv.

What noise are you trying to measure. To test the alternator, you would be looking for AC ripple. Use the multimeter on ac volts, black lead to battery negative and red lead to battery positive on back of alternator. The reading should be less than 0.5 volts (500 mV). The Fluke meter is up to the requirement.

 

[The motor guy]

What noise are you trying to measure. To test the alternator, you would be looking for AC ripple. Use the multimeter on ac volts, black lead to battery negative and red lead to battery positive on back of alternator. The reading should be less than 0.5 volts (500 mV). The Fluke meter is up to the requirement.

Come again? .05 is 50mv you want less than 50 and I thought the red positive lead goes to the big wire on on the back of the alternator and you ground the black one to the negative terminal or I guess the alternator housing too if you want. My fluke 323 only reads 100mv or .1

 

[The motor guy]

I'm going to do what Chris said and go to the auto parts store. I thought they had to bench test it, didn't know they did it on the vehicle.

 

[Fredxt]

Still trying to test my alternator for ac noise, but it seems my fluke meter isn't good enough. 100mv is the least amount it will measure and ac noise for an alternator isn't suppose to be more than 50mv.

I have this one

https://www.amazon.com/gp/product/B07Z67MMGC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

and it measure alternator noise FWIW

 

[4329]

Come again? .05 is 50mv you want less than 50 and I thought the red positive lead goes to the big wire on on the back of the alternator and you ground the black one to the negative terminal or I guess the alternator housing too if you want. My fluke 323 only reads 100mv or .1

0.5 volts is 500mV. The Red lead off your multimeter goes to the postive wire on the back of the alternator.Please read the attached Fluke information. If you are not familar with multimeters this info will help. You could use autorange on the fluke multimeter on AC volts, what model Fluke do you have.

Come again? .05 is 50mv you want less than 50 and I thought the red positive lead goes to the big wire on on the back of the alternator and you ground the black one to the negative terminal or I guess the alternator housing too if you want. My fluke 323 only reads 100mv or .1

0.5 Volts is 500mV. The red postive lead from you Fluke goes to the postive wire on the back of the alternator.Use the autorange function on ac volts. Please find attached Fluke pdf that may help you understand testing of alternators. What Fluke meter do you have.

Come again? .05 is 50mv you want less than 50 and I thought the red positive lead goes to the big wire on on the back of the alternator and you ground the black one to the negative terminal or I guess the alternator housing too if you want. My fluke 323 only reads 100mv or .1

Figure 4. Checking ripple voltageRipple voltage or (ac voltage) can be measured by switching your DMM to ac and connecting the black lead to a good ground and the red lead to the “BAT” terminal on the back of the alternator, (not at the battery).A good alternator should measure less than .5 V ac with the engine running. A higher reading indicates damaged alternator diodes.

The above is taken from the Fluke Beat Book. 0.5V is 500mV, try Google. What model Fluke do you have, the manual will give you the specs on the meter and how to use it. Autorange is very usefull if measuring unkown voltages.

 

[The motor guy]

0.5 volts is 500mV. The Red lead off your multimeter goes to the postive wire on the back of the alternator.Please read the attached Fluke information. If you are not familar with multimeters this info will help. You could use autorange on the fluke multimeter on AC volts, what model Fluke do you have.

0.5 Volts is 500mV. The red postive lead from you Fluke goes to the postive wire on the back of the alternator.Use the autorange function on ac volts. Please find attached Fluke pdf that may help you understand testing of alternators. What Fluke meter do you have.

Figure 4. Checking ripple voltageRipple voltage or (ac voltage) can be measured by switching your DMM to ac and connecting the black lead to a good ground and the red lead to the “BAT” terminal on the back of the alternator, (not at the battery).A good alternator should measure less than .5 V ac with the engine running. A higher reading indicates damaged alternator diodes.

The above is taken from the Fluke Beat Book. 0.5V is 500mV, try Google. What model Fluke do you have, the manual will give you the specs on the meter and how to use it. Autorange is very usefull if measuring unkown voltages.

Okay. Well he said the opposite

 

[4329]

Okay. Well he said the opposite

Opposite to what,the red lead fom your multimeter goes to the positive on the alternator, I expected you to understand that I was referring to the black and the red leads from your multimeter,did the info help you, what model fluke are you using.

 

[The motor guy]

So when you do this ripple test, do you turn all the accessories on? Like radio, lights, hvac etc?