Is there a cheap DC Clamp Meter with 200A AND mA resolution?

[elfer]

I've been looking at DC clamp meters recently, for automotive use.  Primarily, I want to be able to verify that rebuilt alternators are capable of producing their rated output, which would be 90-150A, depending on the model.  But it would also be nice to verify that a car doesn't have a parasitic drain, which would require measuring 30-40mA with a reasonable degree of accuracy.   I have a couple of Uni-T DMMs that I've been happy with so looked at their offerings first.  The UT210D would meet my main requirement but the specs quote 2%+/-3 counts accuracy at the minimum 10mA resolution, which I interpret as saying it could be off by 30mA, or 100%, when measuring 30mA.  So, for that task, I'd be better off with the UT210E, which resolves to 1mA at a accuracy of 2%+/-8, or 9mA at 30mA, which would be much more meaningful.  (And I've found the long thread about the 210E and know it's a popular choice here!).  But sadly it won't do the higher currents above 100A that I'm looking for for alternator testing.

Before I end up buying one of each, does anyone know a single clamp meter that could meet both requirements? Measure up to 150A and resolve down to 1mA? (or to 10mA with +/- 1 count accuracy?)  It would have to cost less than buying both a UT210D and a UT210E to be worth getting instead, though if it had a Peak Hold feature I could talk myself into spending a little more..  

[Martin72]

Hi,

A clampmeter with such specs and ranges....and cheap.
Tell me when you found one.
OK, let´s get serious:
Even when costs are not important, I don´t know a clampmeter which could handle both, hundreds of A and also mA, I´m afraid, you must buy 2.
At work, I got a Fluke337 and a Benning CM11 and it´s perfect - But costs "a lot".
Measuring mA with acceptable accuracy with a clampmeter...I got a UT-210E here, will test it after lunch how it performs in that range against an calibrated BM869s.
If it´s "good enough", you should buy it plus another clampmeter.

[elfer]

"A clampmeter with such specs and ranges....and cheap.
Tell me when you found one. "

That made me laugh   You make a good point, I'm probably asking the impossible.  The UT210E low current accuracy I'd be happy with but it won't do the high current.  I do suspect I'll end up buying two meters.

Gruß

[BravoV]

Your quest is like finding a "cheap" weighing scale than measure few grains of rice that weight probably few grams with 1 gram accuracy, yet it can accurately measure the weight of a car, yet with 1 gram accuracy.

If its cheap, I want it too. 

[elfer]

Yeah.  It's just frustrating that the 100A max of the 210E is not quite enough.  I might just start with one of those and be satisfied that "OL" would verify an alternator is providing at least 100A, even if I couldn't verify its max output.

(Or I might start with the 210D and know I can always still use an inline DMM to measure parasitic battery drain )

[fourfathom]

I've got a few DC clamp ammeters (a Fluke, and a couple cheap ones), and when I need to measure mA I use a multi-turn coil through the jaws.  This is easy if the wires carrying the current are skinny and have enough excess slack, but pretty much impossible on a car -- you have to disconnect the cable and at that point you might as well use a regular ammeter.  You can double the sensitivity of a clamp-meter by passing the positive cable through the clamp, and the negative cable through in the opposite direction.  This might be possible with car wiring, but probably not.

[SilverSolder]

I use the UT210E at 200A like this:   I made a "calibrated piece of wood" that holds the clamp open just wide enough to drop the reading by half (about 4mm - 5mm if I remember correctly).  I calibrated it by wrapping a wire 10 times around the clamp and running 1A through it from a bench power supply, shaving the wood block down with a hobby knife until the reading was exactly 5A.  It works surprisingly well for such a cheap hack!

[Martin72]

 

MMD

[SilverSolder]

MMD

The calibrated piece of wood stores easily in the pouch along with the meter, ready for use any time! 

[elfer]

I don't know how well I'd be able to replicate that but I love the idea!  There'd be no harm in me giving it a go anyway 

[SilverSolder]

I don't know how well I'd be able to replicate that but I love the idea!  There'd be no harm in me giving it a go anyway 

I'll take a picture and an accurate measurement and post here a bit later on.  It's my favourite hack of 2020! 

[Martin72]

mA current measures, comparing Brymen 869s calibrated vs UT210E, first a normal resistor, then a electronic ( chinese crap) load with 10mA steps.

10.00mA/12mA
15.10mA/19mA
20.22mA/21mA
25.06mA/26mA
30.42mA/34mA
35.25mA/40mA
49.01mA/47mA
59.11mA/59mA
69.10mA/68mA
78.95mA/75mA
88.90mA/86mA
98.96mA/98mA

Range Brymen: 400mA(probably), range UT210-E : 2A
Before every measurement, I´ve pressed the zero-button of the clamp.
Values are depending of the position wire-jaws.

Martin

[elfer]

thanks Martin.  Those 210E results are more than accurate enough for my needs.  If only the 210D could be relied on to be within +/- 10mA at those sort of currents it'd be close enough for me.

[Trader]

thanks Martin.  Those 210E results are more than accurate enough for my needs.  If only the 210D could be relied on to be within +/- 10mA at those sort of currents it'd be close enough for me.

AFAIK you can hack the 201E to 1,000A and 10,000 counts.

[elfer]

thanks Martin.  Those 210E results are more than accurate enough for my needs.  If only the 210D could be relied on to be within +/- 10mA at those sort of currents it'd be close enough for me.

AFAIK you can hack the 201E to 1,000A and 10,000 counts.

I'd seen that increasing the count was possible but missed that one could increase the max measurable current.  That's something I could potentially explore.  It could be a fun winter lockdown project learning how to read and write to eproms!

[elfer]

Just to thank everyone for taking the time to reply and offer advice.  I've ordered the 210E for now and will see if I can get by with just that 

[SilverSolder]

thanks Martin.  Those 210E results are more than accurate enough for my needs.  If only the 210D could be relied on to be within +/- 10mA at those sort of currents it'd be close enough for me.

AFAIK you can hack the 201E to 1,000A and 10,000 counts.

I'd seen that increasing the count was possible but missed that one could increase the max measurable current.  That's something I could potentially explore.  It could be a fun winter lockdown project learning how to read and write to eproms!

It may be possible to reprogram the computer inside it to go up to 1,000A but will the Hall effect sensors in the clamp be up to the task with a 10x overload?

[kbrill]

Have made charging system and parasitic measurements on a variety of vehicles . Charging system measurements are easy and even low cost clamp on probes will work fine . Consistency of reading is more of an issue with oversize aperture .

Low level parasitic measurements are more frustrating as probe head size and geometry make placement over wires in the available space difficult and sometimes impossible . Often I must try a variety of probes in order to find one that will fit .

It is very tempting to purchase a higher amperage range instrument than necessary . resist the urge and look for smallest head and aperture .

[Hydron]

Certainly worth getting one and having a go at an EEPROM hack - even if >100A doesn't work out the UT210E is worth having for the low range.

I would check that it remains accurate at the higher currents (wrap a few turns around it to multiply a known test current), and that any magnetisation from the high currents doesn't cause any offset issues when subsequently measuring low currents.

[Martin72]

I did measure comparisons UT-210E vs a calibrated high accuracy poweranalyzer and postef it in the Uni-T thread.
When I find it, I´ll post a link here.

[SilverSolder]

Here is the "calibrated piece of wood" hack to read 200A with a UT-210E by creating an air gap in the magnetic circuit.

Basically, it causes the sensitivity to drop by half so 100A on the display means 200A actual current.

The wood needs to be 6.25mm thick (at least on my example).

[mansaxel]

Alternative, non-economical, complicated, not-what-you-asked-for vintage solution:

Find an used -hp- 428b for low amps (up to 10A) measurement (better than 5% accuracy on 1mA FSD) and a good modern clamp for high amps.

Attached image is a 974a and the 428b both measuring a "100mA" current from a bench PSU. After the required 15 minute warm-up of the valve-based wiggly-pointer meter...

[elfer]

Alternative, non-economical, complicated, not-what-you-asked-for vintage solution:

Find an used -hp- 428b for low amps (up to 10A) measurement (better than 5% accuracy on 1mA FSD) and a good modern clamp for high amps.

Attached image is a 974a and the 428b both measuring a "100mA" current from a bench PSU. After the required 15 minute warm-up of the valve-based wiggly-pointer meter...

 

[Trader]

Attached image is a 974a and the 428b both measuring a "100mA" current from a bench PSU.

@mansaxel, this is an off-topic post, but your HP 974A is an awesome DMM, maybe 26 years old, and seems to be as good as other "modern" 50k/60k counts DMMs (Fluke 189, 289, Keysight U1282A, Brymen BM869s, BM869s, BM789, etc)

https://literature.cdn.keysight.com/litweb/pdf/5967-6368EN.pdf

Reinforce my idea of investing in excellent instruments where you can use them with confidence throughout your whole life.

I wonder, what is the First good 50k/60k (100kHz AC, AC-DC, etc...) handheld DMM?

[mansaxel]

Attached image is a 974a and the 428b both measuring a "100mA" current from a bench PSU.

@mansaxel, this is an off-topic post, but your HP 974A is an awesome DMM, maybe 26 years old, and seems to be as good as other "modern" 50k/60k counts DMMs (Fluke 189, 289, Keysight U1282A, Brymen BM869s, BM869s, BM789, etc)

Best part of the 974a story is that I bought it for about $100 
I guess because it predates the IEC safety categories and thus won't tick a box in someone's inventory.

I wonder, what is the First good 50k/60k (100kHz AC, AC-DC, etc...) handheld DMM?

The Fluke 8060 is a worthy contender, even if it's not as many digits precision. But it'll go very high in frequency for its age.

Continuing the "vintage" streak, one can argue for the -hp- 427 to be the first good handheld (I'm using "battery operated" as equivalent to "handheld" here, which is a bit of a stretch, but.) since it was made to be quite competent (but not as the 410c), portable, and compact. It is flat within 2% of FS to 1MHz on AC, which few DMM manage today. It responds well to 3,5MHz, but not as flat. It does lack current measurement. (But I've got an Avometer and its german cousin the Elavi 3 to do such things, apart from the 428b, of course)  I've removed the battery from mine, and run it as a desk meter.

If we're taking the thread back to topic, I'd buy the UT-210E and look for a used AC/DC clamp meter for the higher readings. Or buy another UNI-T.