What's a good clamp on meter for house and car use?

[ovilla]

My air conditioner is all of a sudden popping the 40amp circuit breaker and now the battery in one of my cars is dead (again). What's a good meter that can do both AC and DC measurements? I'm hoping to stick to a $100-150 budget and would use it about as often as my DMM (maybe 2-3 times a month). I also want something that I can check the amp draw on at least a 50amp circuit. Just thinking for down the road if/when I get a welder. Thanks

[Charles (in GA)]

Most clamp on amp meters do not do DC. If you find one that does, it will be pricey.

Charles

[Dodgepu360]

I have a craftsman pro AC/DC clamp meter its works great it was around $100 this one (http://www.sears.com/sr/javasr/product.do?cat=Electrical+Shop&pid=03473756000&vertical=TOOL&subcat=Multi-Meters%2C+Testers+%26+Accessories&BV_UseBVCookie=Yes)

[RPH]

Sears unit looks to be a decent one for home use. Upto 800 amps DC, not bad for the money.

[ovilla]

I know this is a stupid question but I'm going to ask it anyway. Does the Craftsman meter mentioned above tell you in amps the amperage draw of a circuit? I've read about some other meters giving you volts, which you then have to use in a calculation to figure out the amperage draw. Seriously, I want to measure my air conditioners fan current draw and see if it's within it's nominal range and not have to break out a calculator.

[MAD]

I know this is a stupid question but I'm going to ask it anyway. Does the Craftsman meter mentioned above tell you in amps the amperage draw of a circuit? I've read about some other meters giving you volts, which you then have to use in a calculation to figure out the amperage draw. Seriously, I want to measure my air conditioners fan current draw and see if it's within it's nominal range and not have to break out a calculator.

Yes, it will tell you the current draw in amps.

In order to measure amperage with the clamp you will have to find or create a place where you can clamp around one conductor (wire) at a time. It will not work to clamp around the entire power cord. This can be done by taking the cover off of your breaker panel and clamping around each wire for the circuit where it goes into the breaker. You can clamp on anywhere in the circuit or inside the appliance where you can clamp around the conductors individually or you can make a small extension cord with individual wires and the proper connectors and clamp on there.

[Charles (in GA)]

The Craftsman meter mentioned above is a very good meter for the money. I have looked at many meters in the Grainger Superstore I frequent and most are not true RMS, just the expensive ones, and many (most?) do not do DC amps. This includes several common name brands.

I have an older A W Sperry clamp on analog meter with the rolling drum type dial. I really like it, but a digital would be nice. I might have to look at the Craftsman.

Charles

[ovilla]

What is true RMS? I keep seeing this advertised but have no idea what it is. Thanks

[Fast Orange]

Without getting into a long discussion on electric theory,a non-RMS meter measures the approxiamate peak voltage in a sine wave AC circuit,while a RMS meter measures the root/mean squared area under the sine wave.True RMS is a more accurate measurement of the effective voltage in a circuit.This different way of measuring voltage is needed when troubleshooting circuits for electronic equipment that may be affected by harmonic distortion of the AC sinewave.Unless you are doing work in a computer room or other sensitive area,the peak voltage readings are accurate enough for most electrical work.Of course,almost all automotive work is DC,so True RMS vs. peak readings are of no consequence.

George

[MAD]

What is true RMS? I keep seeing this advertised but have no idea what it is. Thanks

A true RMS Voltmeter will provide a more accurate measurement of AC voltage anytime the electrical wave form is not a true sine wave. I have a true RMS meter that I use for adjusting the output curve of an old analog controlled Theatrical dimming system I am responsible for maintaining. Non TRMS meters are referred to as averaging meters. For basic electrical work you do not need true RMS.

[W-Cummins]

BTW the Crapsman meter above is not a RMS meter, and the one review that it received on the sears site is not exactly glowing:(

That is about the price I paid for my Fluke 33 when I got it (new), a few years ago off fleebay


William...

[RPH]

I have the Fluke 337 amp meter, true rms but only to 400 hertz. As I work on high frequency equipment it's only use to me is for the DCA at 1000 level. Household / garage will not require true RMS feature.
Fluke 337 about $375.00. Also I have worn out Flukes 87 DVM's.

[MAD]

BTW the Crapsman meter above is not a RMS meter, and the one review that it received on the sears site is not exactly glowing:(

William...

I do not think think that reviewer on the Craftsman site knows what he is talking about. Lots of Meters will give you a very low random fluctuating voltage reading when they are not connected to a circuit (or the circuit is open) This especially true when the meter is set in the lower ranges.

I do not know about the quality of the clamp-on meter Craftsman sells now. I can say that the Craftsman amp meter that I bought around 12 years ago has had no problems after quite a bit of professional use.

[W-Cummins]

I have the Fluke 337 amp meter, true rms but only to 400 hertz. As I work on high frequency equipment it's only use to me is for the DCA at 1000 level. Household / garage will not require true RMS feature.
Fluke 337 about $375.00. Also I have worn out Flukes 87 DVM's.

you can get a new 337 for about $230 on ebay and here (http://cgi.ebay.com/Fluke-337-clamp-meter_W0QQitemZ170107940529QQihZ007QQcategoryZ2541 2QQssPageNameZWDVWQQrdZ1QQcmdZViewItem) is a used one that went for $136 that looks clean.

As for the worn out 87's if they are of recent vintage, they now have a life time warranty. So send them in and have the fix them!

William...

[Charles (in GA)]

BTW the Crapsman meter above is not a RMS meter,...

How so? The online description says its True RMS, and owners manual states in several places that it is True RMS. Why do you say it is not?

Charles

[SteveU]

I just bought a sheffield research/GTC SR CM100 AC/DC 100 amp digital amp clamp meter for 137.26 shipped to the house from Tooltopia which would work for what you want. I just got it a couple days ago so haven't had much time to play with it but found out as another posted that it won't take a reading if you do the entire cord. It has peak hold on the reading so you can measure starting current as well as normal draw. Will come in useful for balancing circuits & seeing which ones have extra capacity.

[ranger_dood]

To get to your point of the A/C popping the 40 amp breaker, is it doing it right away, every time? Or is it only every so often? If it's right away, my bet is on the compressor start capacitor. A simple job to replace,if you have soldering ability.

[ovilla]

The AC is popping the circuit every so often (3 times one day and only once another day). I know the AC unit itself is most likely the culprit but am also wondering if the 40 amp circuit breaker is bad. Do circuit breakers ever go bad? I stood next to it the other day and it was making a lot of noise (about a minute or two of gurgling) before the circuit popped. Hence, I want to measure the amperage to see if it's even getting close to the 40 amp rating of the circuit breaker before it pops. By the way, my AC unit is only 5 years old and is an older 10 SEER unit.

[MAD]

The AC is popping the circuit every so often (3 times one day and only once another day). I know the AC unit itself is most likely the culprit but am also wondering if the 40 amp circuit breaker is bad. Do circuit breakers ever go bad? I stood next to it the other day and it was making a lot of noise (about a minute or two of gurgling) before the circuit popped. Hence, I want to measure the amperage to see if it's even getting close to the 40 amp rating of the circuit breaker before it pops. By the way, my AC unit is only 5 years old and is an older 10 SEER unit.

Yes circuit breakers go bad. They often get weaker (easier and easier to trip) each time the breaker trips. Circuit breakers can handle a small overload for a short period of time such as the momentary large current draw when a motor starts. For this reason you may need to do some research to find out what the normal current draw is when the unit starts as well as when it is running. If a motor is having difficulty starting this momentary large current draw will be prolonged and can trip the breaker. Any loose or corroded electrical connections can also increase current draw as well.

If the ac unit sounds normal when the compressor kicks in, I would check to see if the 40 amp breaker is the recommended size and replace it if it is. The breaker is cheap. If a larger breaker is specified, make sure the wire is the proper size before installing a larger breaker.

And of course, be careful.

[ovilla]

Great advice everyone. I do appreciate it. The AC unit starts up and runs smoothly and is actually quite quiet and all you hear is the humming of the fan. I think I'll swap out the breaker after I buy my new meter. I've been wanting to get one of these clamp on meters and this is the perfect excuse.

[bmwpower]

Seems like these things are pretty useful. Time to add it to my Christmas list.

As far as how you clamp it to the wire, does the wire have to be between the ends of the clamp OR does it merely have to be within the arms of the clamp?

From the Craftsman site review for the meter:

"I have this meter and i will never buy another one like it.I seen the features and the price and wanted this meter bad. I am an a/c man and need to check capacitors ,amps ,temperature and volts.This meter gives readings (in the volt mode) when nothing is beeing measured.Which means when I am checking across a switch or fuse my meter reads volts no matter what.I am very unsatisfied with this meter and do not feel safe using it."

Sounds like it's defective, no?

[Fast Orange]

In my experience,most digital VOM meters will show some phantom readings-usually less than 1 volt-when in a lower scale voltage mode.I don't have an explanation of why,but I suspect it has something to do with the sensitivity of the meter and any EMF in the area being worked in.Digital meters are great for absolute accuracy,in that any bad readings due to parallax,scale confusion and operator error are reduced or eliminated,but for general use and anytime you need to watch changing readings,I prefer a quality analog meter.I've got an old Simpson 260 multimeter that gets sent in for calibration and maintenance every few years that I use 90% of the time.I also have a couple of digitals-Fluke and Sperry that are very accurate and easy to use,but tracking changing values on them isn't my favorate thing-kind of like trying to use a digital tachometer in a race car.You can't read the numbers as fast as they flash by.The same thing holds true for clamp on ammeters-I've got both an analog 400A and digitalAC/DC 1000A Amprobe meters.The digital is great for static and peak readings,but rapidly changing readings give you a headache.

George

[MAD]

From the Craftsman site review for the meter:

"I have this meter and i will never buy another one like it.I seen the features and the price and wanted this meter bad. I am an a/c man and need to check capacitors ,amps ,temperature and volts.This meter gives readings (in the volt mode) when nothing is beeing measured.Which means when I am checking across a switch or fuse my meter reads volts no matter what.I am very unsatisfied with this meter and do not feel safe using it."

Sounds like it's defective, no?

I do not think think that reviewer on the Craftsman site knows what he is talking about. Lots of Meters will give you a very low random fluctuating voltage reading when they are not connected to a circuit (or the circuit is open) This especially true when the meter is set in the lower ranges.

.

[QUOTE=bmwpower;106082]Seems like these things are pretty useful. Time to add it to my Christmas list.

As far as how you clamp it to the wire, does the wire have to be between the ends of the clamp OR does it merely have to be within the arms of the clamp?

You clamp around the wire (one conductor at a time). You do not actually clamp on it or pinch the wire.

[MAD]

The AC is popping the circuit every so often (3 times one day and only once another day). I know the AC unit itself is most likely the culprit but am also wondering if the 40 amp circuit breaker is bad. Do circuit breakers ever go bad? I stood next to it the other day and it was making a lot of noise (about a minute or two of gurgling) before the circuit popped. Hence, I want to measure the amperage to see if it's even getting close to the 40 amp rating of the circuit breaker before it pops. By the way, my AC unit is only 5 years old and is an older 10 SEER unit.

If you could hear the breaker chattering for a minute or two as you describe and the compressor seems to start up normally, I would also check (or have someone check) to see if you have a loose connection somewhere. Loose wire nut, screw terminal on breaker, weak clip where breaker goes on buss, etc... Look and listen for signs of arching-connections with a dark pitted appearance, smells like you drove with your parking brake on, or the sound of crackling or buzzing when the circuit is live are things to look for.

[W-Cummins]

How so? The online description says its True RMS, and owners manual states in several places that it is True RMS. Why do you say it is not?

Charles

My mistake!
I did not notice it in the item name, it is not listed in the item description or the specs on the web page (I also didn't download the manual)

I will also admit that the reviewer is a little unclear about his "problem" with the meter:-) it seems to say that he sees a voltage on the open floating leads, ( not bad ) and also seems to say he sees it when he tests devices that don't have any voltage applied ( bad ) ....

William...