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DC Amp Clamp #5406890 04/18/20 10:47 AM
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painfx Offline OP
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Anyone tried these? How accurate is it on low DC amp reading? How is the quality life span?

https://www.amazon.com/gp/aw/d/B00O1Q2HOQ/ref=ox_sc_act_image_1?smid=A1YTNFKMSJ8RNW&psc=1

Re: DC Amp Clamp [Re: painfx] #5406910 04/18/20 11:15 AM
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JHZR2 Offline
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I have an extech, as well as an external clamp for my fluke meter, and a cheapo one for my spare garage. I think the question is how much current are you looking to measure?

Ive not found that any are great in the <2A regime. My Extech 380942 is notionally the best, but all of these are contingent on getting a good zero. DC is harder to measure than AC, and its easy to get a half-ampere variation between units at the same spot. Some of that is probably design/build differences, Ive never tried to calibrate any of them by say, putting 2A through the 10A leads on a good multimeter, and then verifying the reading of the clamp on.

Im telling you this because I had high hopes that the 0.1mA resolution of the Extech would be useful for measuring trickle charge rates into batteries, and parasitic loads from vehicles, but ive never been truly sure. Sometimes Ill even see negative readings in the mA regime when I know it cant be. Again, its so contingent on getting the right DC zero, and its hard to do that in changing environments.

But as a basic tool to check, knowing that you might be off by some reasonable amount, Id say its OK...

How much resolution do you need, and is it something you cant use the 10A feed through setting on a multimeter?

Re: DC Amp Clamp [Re: JHZR2] #5406919 04/18/20 11:23 AM
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supton Online Content
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Originally Posted by JHZR2

Ive not found that any are great in the <2A regime. My Extech 380942 is notionally the best, but all of these are contingent on getting a good zero. DC is harder to measure than AC, and its easy to get a half-ampere variation between units at the same spot. Some of that is probably design/build differences, Ive never tried to calibrate any of them by say, putting 2A through the 10A leads on a good multimeter, and then verifying the reading of the clamp on.

Im telling you this because I had high hopes that the 0.1mA resolution of the Extech would be useful for measuring trickle charge rates into batteries, and parasitic loads from vehicles, but ive never been truly sure. Sometimes Ill even see negative readings in the mA regime when I know it cant be. Again, its so contingent on getting the right DC zero, and its hard to do that in changing environments.

Could try finding some mu-metal to wrap around it, I would guess stray magnetic field (or even earth's field) interacting here. Make sure nothing is carrying current near the meter, like a few inches away from other high current paths.


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Re: DC Amp Clamp [Re: painfx] #5406922 04/18/20 11:25 AM
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I bought the tacklife dc amp meter last year and really like it. I used it to measure the output of vehicle alternators. Part number cm01a.


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Re: DC Amp Clamp [Re: joegreen] #5406931 04/18/20 11:35 AM
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JHZR2 Offline
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Originally Posted by joegreen
I bought the tacklife dc amp meter last year and really like it. I used it to measure the output of vehicle alternators. Part number cm01a.


That sort of thing, any of these will be fine. because youre measuring many amperes most of the time, and evena half amp likely doesnt matter in the big scheme of things.

Its when you get way low that the noise these things pick up becomes more of an issue. And if youre wedging it under the hood of a car in some random spot, it can be hard to manage.

One just has to accept these things as good enough, IMO, even if getting a super good, NIST traceable one.

Re: DC Amp Clamp [Re: JHZR2] #5406936 04/18/20 11:45 AM
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painfx Offline OP
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Originally Posted by JHZR2
I have an extech, as well as an external clamp for my fluke meter, and a cheapo one for my spare garage. I think the question is how much current are you looking to measure?

Ive not found that any are great in the <2A regime. My Extech 380942 is notionally the best, but all of these are contingent on getting a good zero. DC is harder to measure than AC, and its easy to get a half-ampere variation between units at the same spot. Some of that is probably design/build differences, Ive never tried to calibrate any of them by say, putting 2A through the 10A leads on a good multimeter, and then verifying the reading of the clamp on.

Im telling you this because I had high hopes that the 0.1mA resolution of the Extech would be useful for measuring trickle charge rates into batteries, and parasitic loads from vehicles, but ive never been truly sure. Sometimes Ill even see negative readings in the mA regime when I know it cant be. Again, its so contingent on getting the right DC zero, and its hard to do that in changing environments.

But as a basic tool to check, knowing that you might be off by some reasonable amount, Id say its OK...

How much resolution do you need, and is it something you cant use the 10A feed through setting on a multimeter?


My purpose is to use it to check parastic drains. Although I do have a Fluke DMM, there are times, connecting in series with the negative battery is not ideal. This DC Amp clamp looks good from it's review, but I just wanted a second opinion. It doesn't have to be 100% accurate, but accurate enough to determine if a parastic draw is too high.

I also looked at ones that were over $100+ in price range, but that does not mean it will much accurate. I checked brands like Electronic Specialties, C-100, and etc... On youtube, people have compared this cheap one with the $100+ ones and this one was quite accurate, if not, much accurate than some of the $100 ones.

Re: DC Amp Clamp [Re: painfx] #5406993 04/18/20 01:18 PM
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When I followed your link it turns out I ordered that exact meter a bit over a year ago. I have found it to be accurate but as others have said you have to orient the clamp in the same exact position as you will be clamping it onto the wire and zero it and in relatively close proximity to the wire, then you move to the wire and clamp it over and try to center the wire and align it with the arrows on the clamp. Just turning the clamp 90 deg from zero position to measurement position can cause a variation of 15 or 20 ma depending on the environment. So having it face up to look at the reading and then clamping to a horizontal wire with the display to the side will cause inaccuracies. It worked fine for me when I was looking to see how long the car was running tests before it dropped to normal standby drain 150ma down to 90ma and finally to 40ma were all very easily seen.

I also used it to see what my trolling motor was drawing under different load conditions in the 50A to 12A range. Very handy meter. I just wish it could measure higher current to check my truck starter current but that meter is not as sensitive at the lower range.

Last edited by samven; 04/18/20 01:20 PM.
Re: DC Amp Clamp [Re: painfx] #5407341 04/18/20 09:29 PM
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This thread is interesting to me, so I pulled some gear out. I put a battery on a charger with a battery minder.

To get it so that I could try the A and mA ranges, I had to switch between meters. I had blown the 400mA in my big fluke, so it worked out (meters won’t allow dual current paths).

I did a dry run connecting the charger to the battery, and went about my way. I was pleased to see good alignment.
[Linked Image]

I wanted to test the A vs mA readings, so I had to disconnect and start again. I ran with the charger in constant voltage mode. The battery was fully charged so the current dropped rapidly, as expected.

[Linked Image]

Once the current was below 400, I put the two meters in parallel, the big one in 10A mode, the smaller one in mA mode. They shared about 60/30% (sensible since the 10A path will be lower resistance) and then I pulled the lead on the bigger meter.

[Linked Image]

Left it for a number of hours, meters went to sleep, then I woke them back up. I didn’t set the smaller meter on dc mA, so the reading is not correct. frown
[Linked Image]

Different readings were strange, so I removed both clamp meters and re-zeroed them.

[Linked Image]

So that’s strange. But I figured this might be insightful for showing folks my concerns and why I have somewhat of a lack of confidence in truly knowing what is the right value...

Re: DC Amp Clamp [Re: samven] #5407926 04/19/20 03:40 PM
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painfx Offline OP
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Originally Posted by samven
When I followed your link it turns out I ordered that exact meter a bit over a year ago. I have found it to be accurate but as others have said you have to orient the clamp in the same exact position as you will be clamping it onto the wire and zero it and in relatively close proximity to the wire, then you move to the wire and clamp it over and try to center the wire and align it with the arrows on the clamp. Just turning the clamp 90 deg from zero position to measurement position can cause a variation of 15 or 20 ma depending on the environment. So having it face up to look at the reading and then clamping to a horizontal wire with the display to the side will cause inaccuracies. It worked fine for me when I was looking to see how long the car was running tests before it dropped to normal standby drain 150ma down to 90ma and finally to 40ma were all very easily seen.

I also used it to see what my trolling motor was drawing under different load conditions in the 50A to 12A range. Very handy meter. I just wish it could measure higher current to check my truck starter current but that meter is not as sensitive at the lower range.


Awesome! Thanks for the tips! Looks like I'm going to pull the trigger and buy it! smile

Re: DC Amp Clamp [Re: JHZR2] #5407939 04/19/20 03:48 PM
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painfx Offline OP
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Originally Posted by JHZR2
This thread is interesting to me, so I pulled some gear out. I put a battery on a charger with a battery minder.

To get it so that I could try the A and mA ranges, I had to switch between meters. I had blown the 400mA in my big fluke, so it worked out (meters won’t allow dual current paths).

I did a dry run connecting the charger to the battery, and went about my way. I was pleased to see good alignment.
[Linked Image]

I wanted to test the A vs mA readings, so I had to disconnect and start again. I ran with the charger in constant voltage mode. The battery was fully charged so the current dropped rapidly, as expected.

[Linked Image]

Once the current was below 400, I put the two meters in parallel, the big one in 10A mode, the smaller one in mA mode. They shared about 60/30% (sensible since the 10A path will be lower resistance) and then I pulled the lead on the bigger meter.

[Linked Image]

Left it for a number of hours, meters went to sleep, then I woke them back up. I didn’t set the smaller meter on dc mA, so the reading is not correct. frown
[Linked Image]

Different readings were strange, so I removed both clamp meters and re-zeroed them.

[Linked Image]

So that’s strange. But I figured this might be insightful for showing folks my concerns and why I have somewhat of a lack of confidence in truly knowing what is the right value...


According to the pictures, that is accurate enough for me to buy a DC amp clamp. However, it is tricky on how to clamp it on to get a proper reading.

Re: DC Amp Clamp [Re: painfx] #5409151 04/20/20 11:07 PM
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JHZR2 Offline
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It is tricky. Here’s another example - swapped chargers, did the same experiment.

[Linked Image]

Seems the cheap one can be ok, but sometimes gets duped after big changes. In this case the charge profile just changed from like 1.9A to a few hundred mA over the course of a minute or something, and it failed to track.

Waited a few hours and I think the charger is effectively off. If anything it’s a tiny parasitic load. But note the difference. So when you really want to get to mA levels to look for parasitics, I still don’t know that you can trust these.

[Linked Image]

Re: DC Amp Clamp [Re: JHZR2] #5409328 04/21/20 08:39 AM
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painfx Offline OP
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Thank you for the pics! Im just gonna get it. smile

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