Clamp meter selection and readings - Page 1
Forum section: electronics / testgear

author: fishandchips
author_rank: Regular Contributor
timestamp: October 29, 2020, 07:01:27 pm
content: Hello, I bought a KLEIN Tools CL390 clamp meter as it was the only AC-DC clamp meter available in a local store. It has both AC and DC current measurements and True RMS.https://www.kleintools.com/catalog/clamp-meters/acdc-digital-clamp-meter-auto-ranging-400-ampI need some help to interpret the readings. I set the dial knob on the meter to 40A. I had the voltage wire in the middle of the clamp. When I chose the AC measurement option using the SEL button, it gave me positive values only, at most about 0.3. I released the wire and flipped the clamp meter upside down. I put the wire in the middle of the claw. Again it gave me only positive values, at most about 0.3. When I chose the DC measurement option and had the meter facing up, it gave me negative values, about -0.15. When I flipped it upside down, it gave me values about -0.04. One time the sign kept changing but when I measured again, it gave only negative values of -0.04 the least. What does it mean? Does it mean current in that wire only flows in one direction? Why flipping the meter upside down did not reverse the sign of the readings? Why the amplitude is smaller when measuring using the DC option?The meter does not seem to have high accuracy. It just gave me values in the form of 0.0_ to 0.x. Is there a better clamp meter? My requirements are: high accuracy within 5A, 10A and 15A range, have both AC and DC current measurements, ability for data logging.

author: J-R
author_rank: Super Contributor
timestamp: October 30, 2020, 05:39:40 am
content: Are you measuring a single wire, or a cable with positive/negative or hot/neutral/ground all together?To obtain accurate readings you should try to place the clamp nearest the position where you will take the actual measurement, zero the meter, then clamp the wire and observe the reading.You could get a multimeter that supports your necessary logging features and then use a current clamp that connects to the multimeter's voltage input.

author: fishandchips
author_rank: Regular Contributor
timestamp: October 30, 2020, 12:57:25 pm
content: Quote from: J-R on October 30, 2020, 05:39:40 amI was measuring a single wire. The meter was set to zero before measurements.I got more than one multimeters already. Any recommendation on good current clamp with data logging feature?

author: PushUp
author_rank: Regular Contributor
timestamp: October 30, 2020, 01:27:55 pm
content: Unfortunately, none of my Clamp Meters do have data logging capabilities:But I would definitely go with the cheap Brymen BM 197 which is even usable by TestController - Thank you, HKJ!https://www.eevblog.com/forum/testgear/program-that-can-log-from-many-multimeters/msg3129494/#msg3129494https://brymen.eu/shop/bm197/https://brymen.eu/shop/brua-19x-usb-kit-for-bm197-bm195/...and after that, I would buy the Keysight U1213A while selling both Fluke...https://www.keysight.com/en/pcx-2832426/u1210-series-35-digit-handheld-clamp-meters?cc=GB&lc=engCheers!

author: fishandchips
author_rank: Regular Contributor
timestamp: October 30, 2020, 01:45:16 pm
content: How do we know when to use AC and when to use DC current measurement option?Many meters have 40A, 400A. What so special about 4?

author: HKJ
author_rank: Super Contributor
timestamp: October 30, 2020, 04:06:54 pm
content: Quote from: fishandchips on October 30, 2020, 01:45:16 pmClamp meters are much easier to design for high current than for low current.This means most clamp meters do not have low ranges and if the meter has a low DC range you have to use the zero button all the time. Just turning the meter a bit can change the offset on DC.

author: fishandchips
author_rank: Regular Contributor
timestamp: October 30, 2020, 04:18:07 pm
content: Quote from: HKJ on October 30, 2020, 04:06:54 pmSo even it displays zero, I have to press the zero button all the time before measurement?Why the sign did not change even I flipped the meter?

author: HKJ
author_rank: Super Contributor
timestamp: October 30, 2020, 04:29:37 pm
content: Quote from: fishandchips on October 30, 2020, 04:18:07 pmNo, but you hold the meter close to the wire in the same orientation that you are going to use it in and then do a press on the zero button.Quote from: fishandchips on October 30, 2020, 04:18:07 pmIn DC the sign will flip if the current runs the opposite way through the clamp, in AC it will not change.

author: MosherIV
author_rank: Super Contributor
timestamp: October 30, 2020, 05:27:22 pm
content: AC current measurement is done by measuring the ac coupled magnetic field which gets turned into an AC voltage signal in most clamp meters. No AC current, no AC magnetic feild, no small ac voltage.DC current measurement is done with Hall Effect sensor (measures magnetic fields). These get affected by any magnetic field nearby or even the weak magnetic field of the Earths poles. That is why DC current typically needs to be zeroed.

author: fishandchips
author_rank: Regular Contributor
timestamp: October 30, 2020, 05:54:22 pm
content: I know when we measure the current of AC signal, we use the AC option in the clamp. When we measure the current of DC signal, we use the DC option. How do we know if we are measuring AC or DC signal current?

author: MosherIV
author_rank: Super Contributor
timestamp: October 30, 2020, 05:56:20 pm
content: If you really do not know, using AC setting first, for a DC current it will read 0A. If it reads a value, you know it is AC.Otherwise Switch to DC to measure a DC current

author: jfiresto
author_rank: Frequent Contributor
timestamp: October 30, 2020, 06:53:00 pm
content: TheBenning CM 11can measure DC currents with a resolution of 0.1 mA and an accuracy of +/-1 mA at the low end, but it does no data logging. A least two of us have one and like it.

author: fishandchips
author_rank: Regular Contributor
timestamp: October 30, 2020, 07:01:45 pm
content: Quote from: MosherIV on October 30, 2020, 05:56:20 pmBased on your method and the values I posted in the first post, it means I was meaning AC?

author: HKJ
author_rank: Super Contributor
timestamp: October 30, 2020, 07:49:44 pm
content: Quote from: jfiresto on October 30, 2020, 06:53:00 pmInteresting and it is not that expensive either. I expect to have one shortly.

author: 25 CPS
author_rank: Frequent Contributor
timestamp: October 31, 2020, 01:42:56 am
content: Quote from: PushUp on October 30, 2020, 01:27:55 pmI've got a Keysight U1213A which I bought to supplement/replace a junky Canadian Tire clamp meter and it's been great. The U1213A is actually an older Agilent branded unit that I bought from the Keysight eBay store and I've been happy with it. The only surprise I had was when I first got it and discovered that the battery door it came with didn't have the mount for the optical to USB cable or Bluetooth adapter but Keysight sells the newer battery doors that have the mount as a replaceable part so I ordered it and changed it out. I posted some pictures in the TEA thread showing the original cover and the replacement:Shakedown testing after the retrofit showing that even U1213As shipped without the door that has the mount can be changed out and used to relay data to the remote logging display or to a smart phone etc. which adds logging capability.This meter can do AC, DC, and AC+DC current so it's good for measuring ripple current plus total/peak currents in DC environments in case that's a use case under consideration for you.

author: PushUp
author_rank: Regular Contributor
timestamp: November 01, 2020, 01:15:25 pm
content: Nice find and thanx for sharing this clue, 25 CPS!When I am not mistaken HKJ has the same Clamp Meter and may profit from this info...and afterwards maybe also TestController!Cheers!

author: MosherIV
author_rank: Super Contributor
timestamp: November 02, 2020, 11:27:03 am
content: QuoteSorry, I meant to test it and reply but got distracted and forgot.Just did test just now.With both my clamp meters, measuring DC current in AC mode shows 0AWith my UT210E (this one does both AC and DC amps) measuring AC current in DC mode show 0AFrom your first post - I do not know what the clamp adapter is telling you.

author: geggi1
author_rank: Frequent Contributor
timestamp: November 02, 2020, 07:53:20 pm
content: A few hints about using a clamp meter.1. Dont use a meter that have high range for low currents, because of the accuracy. if an instrument got 1% accuracy it is of the full range. For normal use I pefere to have something with a maximum range of no more than 100A.2. The conductor must go as straight as possible to get an accurate reading.3. If there are a arrow on the clamp meter this is indicating the direction of the current when measuring DC.

author: fishandchips
author_rank: Regular Contributor
timestamp: November 06, 2020, 06:40:12 pm
content: I asked the manufacturer what my test results meant. After waiting for a few days, a technician asked me to call him. I asked him to reply by email and he wrote:You need to be “VERY SPECIFIC” it what you are looking for and what you need the tester/meter to do for youSo even they could not interpret the test results?Since the readings keep changing, I would prefer to buy one that has data logging capability. If I only need accuracy up to about 5A, what meter is recommended?

author: Martin72
author_rank: Super Contributor
timestamp: November 06, 2020, 09:36:26 pm
content: Hi,QuoteThe benning cm11 was already mentioned here - I agree, it´s an accourate instrument, we did an external calibration for this and it´s values are great (example given: ref. current 30mA AC, measured 30mA..).But it could only measure currents of max 10A dc and 20A ac - The price you pay for higher accuracy on lower current ranges.Also it´s got no logging capability.But this could be the choice if you want accuracy more over data logging...

author: fishandchips
author_rank: Regular Contributor
timestamp: November 06, 2020, 11:49:04 pm
content: Quote from: Martin72 on November 06, 2020, 09:36:26 pmI know the cm11 is good but it has no data logging and it is not available in Amazon. That is why I asked for other suggestions.

author: Martin72
author_rank: Super Contributor
timestamp: November 07, 2020, 12:19:20 am
content: What is so special to buy it on amazon ?Apart from this, datalogging seems to be a thing, mostly doing by the cheaper ones which don´t got the accuracy you want.