el cheapo clamp meter - Page 1
Forum section: electronics / beginners

author: silly sausage
author_rank: Regular Contributor
timestamp: January 28, 2025, 07:55:46 am
content: i have a LAP MS2009A clamp meter, It all works except the clamp part, when trying to measure ac amps it reads zero, this is with it clamped to my kettle lead so about a 3kw load, Do the clamp parts in these use a hall sensor or a coil?, I am trying to work out what to check to fix it.

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 09:20:07 am
content: Did you pay attention to this?From the manual:AC Current Measurement1. Place function measuring range switch to ACcurrent measuring range.2. Press the trigger, open clamp head, clip the leadin the clamp to measure the lead current. Note:Clamping two or more leads at the same time willgive invalid reading.3. Read the measuring result from display.

author: MrAl
author_rank: Super Contributor
timestamp: January 28, 2025, 09:31:07 am
content: Quote from: silly sausage on January 28, 2025, 07:55:46 amHello,That is probably because you are measuring the current path and the return current path at the same time. When you do that, it sees the current going one way as positive and going the other way as negative, which subtracts to zero. You have to be able to separate the two wires and measure with just one of those wires. They also sell devices you can plug your appliance into and it separates the two wires so you can measure across just one wire.You can actually measure two or more wires at the same time, but you have to know what the polarity of the current is. If you measure two with the same polarity, the currents will add. This is useful when you want to get more resolution from the clamp meter. If you wind a wire around the clamp two times, you get a reading that is twice as high, so you just divide by 2 to get the actual current level.

author: silly sausage
author_rank: Regular Contributor
timestamp: January 28, 2025, 09:46:31 am
content: thanks,that would explaine it, a case of rtfm! lol.

author: armandine2
author_rank: Frequent Contributor
timestamp: January 28, 2025, 09:52:56 am
content: ..I sent a Kewtech clamp meter back to Amazon - doing that kettle lead test. And I knew (in theory) what I should do, but perhaps in my rush to play with it had a "senior moment". It happens ...

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 10:04:57 am
content: I have made a cable for this.It doesn't look nice, but it works. I don't use it often.

author: Gyro
author_rank: Super Contributor
timestamp: January 28, 2025, 10:12:14 am
content: Ideally you would double insulate those wires. PVC sleeving in the appropriate colours is readily available.

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 10:27:34 am
content: Quote from: Gyro on January 28, 2025, 10:12:14 amYes, that could be done better.I actually only use this to test the clamp meter at mains. Otherwise I use this meter more in ADC mode.If I want to measure the power consumption of my household appliances, I use this device, which is more convenient:

author: Gyro
author_rank: Super Contributor
timestamp: January 28, 2025, 10:42:13 am
content: Yes, for mains stuff, I tend to use a HOPI HP-9800 - much beloved of Big Clive, (after making it safe!) which gives true power, power factor etc. I guess I'm veering away from el cheapo though...https://www.eevblog.com/forum/testgear/hopi-hp-9800-power-meter-(recent)-differences-and-safety-improvements/

author: mwb1100
author_rank: Frequent Contributor
timestamp: January 28, 2025, 11:02:45 am
content: You could get an AC line splitter like this one (with your country's configuration obviously):

author: Gyro
author_rank: Super Contributor
timestamp: January 28, 2025, 11:18:07 am
content: Yes a nice molded line splitter is an ideal solution. Unfortunately the only UK one I've found so far is a TIS one which is rather expensive. It does split out earth leakage in addition to X1 and X10 current though...https://www.testinstrumentsolutions.co.uk/digital-clampmeters-and-accessories/TIS-455-AC-Line-Splitter-with-Earth-Leakage-Measurement

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 11:23:23 am
content: That line splitter is certainly a good solution, but does it only serve to support clamp meters?Isn't it easier to use a power meter directly?I got mine on sale at the time for $5.What do you think?

author: Gyro
author_rank: Super Contributor
timestamp: January 28, 2025, 12:10:05 pm
content: Yes, it is just for clamp meters, but it can allow measurements of things like ground leakage - nothing that can't be done with your split cable though (apart from the current X10 (10 turns through the jaws).P.S. ^ [Edit:Actually ground leakage X10 would have been a more useful inclusion, I just noticed that the PE loop says mA (1000 turns?)]. Yes, plug-in power meters are much more convenient. Obviously at $5 they won't be as accurate as a HOPI with its utility meter IC, but good enough for most applications. The only thing that might be worth checking is the safety of the internal wiring if it's going to be used with high current loads. As you can see from my previously linked thread, even the HOPI was rather dodgy there.

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 01:06:47 pm
content: Quote from: Gyro on January 28, 2025, 12:10:05 pm$5 was the sell-out price many years ago, I don't know what the catalog price was.Voltcraft is a brand of Conrad (Germany). It is specified 16A/3680W.I can use it to test the stand-by consumption of my toothbrush charger. It is 350mW.That's accurate or sensitive enough for me for practical purposes.

author: watchmaker
author_rank: Unknown
timestamp: January 28, 2025, 01:26:16 pm
content: Below is the way we learned in the 1960s.Professionals should NOT try this at work! This was performed by a non professional who is not overly concerned about long term side effects in the controlled environment of his own home.I did order the Fnrisi(?) for $35 and I will compare the readings.