What are the real scenarios where you can use a multimeter to measure current? - Page 1
Forum section: electronics / beginners

author: ksio89
author_rank: Contributor
timestamp: November 05, 2023, 05:26:50 pm
content: Knowing that a current clamp meter is a much better equipment to measure current than a DMM, because not only it's safer for the operator (and for the meter) as it's not in series with the circuit, and also because you can test a live conductor for the same reason, is there any actual pratical scenario where a DMM can be used to measure current? As a hobbyist who just uses a DMM to measure basic stuff like voltage, resistance, continuity etc., I cannot visualise a situation where you need to measure current in electronics equipment. I believe the only situation where you really need to measure current is on large electrical equipment like electrical motors and generators, where the currents involved can be very dangerous.I mean, is it wise to save money and forgo current measuring capability when planning to buy a DMM and use the savings to buy a clamp meter instead?

author: magic
author_rank: Super Contributor
timestamp: November 05, 2023, 05:38:38 pm
content: Clamps are convenient to use but very inaccurate at low currents like a few mA or less.I don't think I have ever used the amps AC range of a DMM, but I have used DC sometimes to accurately measure power consumption of small circuits or quickly check how much current it takes to bring some open collector line to ground, this kind of stuff. OTOH, if I want to measure some current on a breadboard I usually just replace a suitable jumper wire with 1Ω or similar resistor.The process of moving test leads to a separate DMM socket is a bit annoying. Even more annoying is forgetting that they are there and blowing something up...I had this idea once to permanently connect three different colored leads to the three sockets to avoid such mistakes, but I don't use amps often enough to do it.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 05, 2023, 05:40:16 pm
content: I have both DMMs and a clamp meters. If you pick a high quality offering for both categories often times the DMM will have better quality and more accurate ranges especially when relating to basic electronics in measuring lower ranges.But honestly both are nice to have, even if it's just for household repair and diagnostic.

author: Zero999
author_rank: Super Contributor
timestamp: November 05, 2023, 05:40:53 pm
content: A clamp meter is only good for measuring high currents, over a couple of Amps or so.A multimeter can measure low currents much more accurately.

author: ebastler
author_rank: Super Contributor
timestamp: November 05, 2023, 05:41:24 pm
content: That depends very much on what you intend to do. If you are thinking about mains electricity, yes, get a clamp, and you might never need inline current measurement. If on the other hand you are into electronics, maybe battery-operated devices where you want to check and minimize power consumption -- you definitely want current measurement in your multimeter, with mA and µA ranges.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 05, 2023, 05:42:38 pm
content: I recently used it to measure current consumption of a mcu in sleep mode, in the uA range, try to measure that with clamps!Clamps aren't used much in electronics, it's more for electricians.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: November 05, 2023, 05:48:41 pm
content: Dave measures current all of the time in his videos using DMMs and just the jacks.Calculating Battery LifeLooking for a device that is draining your car batterySizing your power supply

author: ksio89
author_rank: Contributor
timestamp: November 05, 2023, 06:16:18 pm
content: I forgot clamp meters are inaccurate at uA and lower ranges, touché. Thanks for the replies folks, guess it's not worth saving a couple of bucks then.

author: armandine2
author_rank: Frequent Contributor
timestamp: November 06, 2023, 11:22:55 am
content: The examples are legion, but I suspect I will soon check my haul of MOVs - and may well use an ammeter

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 06, 2023, 06:07:32 pm
content: If you are going to set the quiescent current (bias) thru radio amp finals and driver BJT transistors, it is often necessary to use a good ammeter,Otherwise the things heat up and blow.

author: SmallCog
author_rank: Frequent Contributor
timestamp: November 06, 2023, 09:18:25 pm
content: Whilst I agree that in electrical a clamp meter is often preferable (high currents at dangerous voltages) there are even situations in electrical where a multimeter is better to measure currentOne is when working with 4-20mA signalsIf you're not familiar, a lot of industrial sensors use a variable current between 4 and 20mA to reflect a scaled realworld measurement (like 0-100psi pressure).Although there are some lovely clamp meters that can measure these signals they're pricy and can easily be read with a multimeter.

author: David Hess
author_rank: Super Contributor
timestamp: November 07, 2023, 02:05:25 pm
content: Power supplies usually have current meters built in, but if they do not, then I often add one of my multimeters in series to measure current.Any time I am working with current sources or transconductance outputs, I may use a multimeter to measure current. Supply current measurements of ICs can reveal what they are doing. A series resistor which could be used to make a current measurement is not always part of the circuit.Input bias current and base/gate current measurements will reveal damaged transistors. This is very useful with operational amplifiers which may have had their inputs damaged by ESD because the bases of the input differential pair are the only thing available which can probed, except for offset null pins.

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 07, 2023, 03:22:36 pm
content: My clamp meter only has resolution to 0.1A forget about microAmp. Besides when measuring DC current it's not as accurate as AC. There are clamp meter that can measure in mA but they are expensive.

author: JJ_023
author_rank: Frequent Contributor
timestamp: November 07, 2023, 03:46:25 pm
content: Quote from: SmallCog on November 06, 2023, 09:18:25 pmThis is not only true but a very common scenario. As a matter of fact there are multimeters with a specific feature that is suited to better measure these particular signals.But like I said before it is nice to have both a DMM and Clamp.

author: Veteran68
author_rank: Frequent Contributor
timestamp: November 07, 2023, 03:55:47 pm
content: Quote from: JJ_023 on November 07, 2023, 03:46:25 pmYeah, it's hard to do serious electronics work with a single meter. I'd consider two DMMs if all you do is low voltage DC work, or a DMM+clamp meter if you need to measure mains/AC currents, as the minimal starting kit.Don't ask me how many DMMs and clamps I own, LOL. And no, that's not all of them in my sig.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 07, 2023, 04:28:35 pm
content: Quote from: ksio89 on November 05, 2023, 05:26:50 pmOf course not. Multimeter is almost always way superior when it comes to SELV electronic projects, because DC clamp meters are massively inaccurate with large bias errors and drifts thereof; often in several amperes; and also way more expensive, whereas a simple, cheap multimeter can easily measure microamperes with a few percents of error.For AC mains current measurement, clamp-on meter is usually a sensible choice because it's non-intrusive and currents areusuallyhigh enough for the clamp meter to handle accurately, plus AC measurement does not have the offset error problem.

author: alligatorblues
author_rank: Regular Contributor
timestamp: November 08, 2023, 07:17:04 am
content: I have a DCmA clamp meter with 1mA, 3mA, 10mA and 3A ranges. It's analog, but very accurate.

author: Dan123456
author_rank: Regular Contributor
timestamp: November 08, 2023, 09:01:52 am
content: I was a mechanic in a previous life and very occasionally would measure current using a DMM.For instance, say a light bulb wasn’t working, I’d fist check the bulb (duh), then the voltage. If it had voltage I might check the current just in case a drop bear had decided to partially chew through the harness or what not.Also, even if I had a clamp back then, I don’t know how much I would have used it as it probably would have sucked half the time due to the lack of space under dashboards and all the wires being in harnesses etc. (not to mention I would still have to take a DMM or test light in at the same time anyways)Not sure if that is still they way auto electricians / mechanics go about it (hell, a lot of mechanics would just remove and replace everything to save time diagnosing stuff back then and imagine that has only gotten worse) but auto electrical is definitely a place I can still see a DMM still being used to measure current in a professional setting

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 08, 2023, 05:36:40 pm
content: Quote from: SmallCog on November 06, 2023, 09:18:25 pmWhen measuring a 4-20mA signal the burden voltage of a DMM in current mode has no effect. Most of the 4-20mA output are good for 0 to 250 Ohms or so.

author: Bud
author_rank: Super Contributor
timestamp: November 08, 2023, 05:40:48 pm
content: You can only position a clamp meter a certain way and reading the display may be difficult. DC mode requires zeroing which is annoying and need to be repeated after the clamp meter moved.

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 08, 2023, 09:15:36 pm
content: Quote from: Bud on November 08, 2023, 05:40:48 pmYou can have clamp meter with remote display or just a clamp attached to a regular DMM. But yeah zeroing the DC amp clamp annoying and if the wire isn't centered in the jaw there could be error.

author: Electro Fan
author_rank: Super Contributor
timestamp: November 08, 2023, 11:07:37 pm
content: These can be helpful for AC:https://www.harborfreight.com/15-amp-professional-ac-line-splitter-57716.html?utm_source=bing&utm_medium=cpc&utm_campaign=425671838&campaignid=425671838&utm_content=1155587907731521&adsetid=1155587907731521&product=57716&store=2963&msclkid=8476d5b48607126c22fbb0f8959a0159