Aliexpress bargain alert- WinApex 268B AC/DC clamp meter

[mikeselectricstuff]

I've had one of these for a while but now listed at 50% off ( may vary by country) - absolute bargain at that price.
https://www.aliexpress.com/item/1005006583519373.html
1mA resolution on clamp DCA, 0.1mA on ACA - ideal for earth leakage measurements.
Really bright, big display, USB rechargeable.

[thm_w]

Review:


4% off in DC mode low current. I think the UT210e is a bit more accurate at DC, but this has a wider range of 6A.

Cheaper here for me $33 shipped: https://www.aliexpress.com/item/1005006582824997.html

[rsjsouza]

Interestingly a few weeks ago I was looking into the whole leakage clamps at Ali. That is a pretty interesting offer for the price; thanks Mike!

[Hydron]

Has anyone opened one up? Wonder how they're safely doing USB recharge. And thanks Mike!

[mikeselectricstuff]

Don't think usb is isolated,but socket is recessed so it's pretty hard to touch, and the unit doesn't operate if charging.

[wraper]

A little bit cheaper here considering free shipping (at least for me). https://vi.aliexpress.com/item/1005006582824997.html

[Aldo22]

Has anyone tested this device below 100mA DC?
I have an ANENG ST212 and it is getting unstable and inaccurate below 100mA.
Is this one better?
In the video you can only see 500mA.

[wasedadoc]

Review:

That reviewer was clueless about using a clamp meter to measure direct current.

[Phil1977]

I have this meter, it´s not too bad.

DC resolution is real, but accuracy is bad compared to shunt meters. It means, if you can place the clamp, zero it and do not touch it anymore then you can see small current changes.

By best guess I´d say accuracy is +/- 2.5% plus +/- 50mA in the DC current mode.

It´s also not very resilient to magnetization. If you expose it to large currents (>50A) or strong magnets, you get quite some hysteresis. I already had the degauss it once.

Has anyone opened one up? Wonder how they're safely doing USB recharge. And thanks Mike!

What do you want to know? I´m quite sure it´s not galvanically isolated to the probe jacks. But the plug is deeply recessed and covered by a tightly fitting and not detachable rubber cap. I did not check if the charging circuit is safe for the LiPo-pouch but just in case this is easily accessible and has a standard plug.

[mikeselectricstuff]

All DC clamp meters are inherently inaccurate at low currents, as they are affected by any stray magnetic field, including Earth's, so are somewhat position dependent.
You need to understand how to use them properly to get the best performance - ideally set it up and zero in the final position with the test subject's power off, then power on without moving the clamp. After measuring, power off and verify that the reading returns to zero. Obviously this isn't always practical, so you need to bear in mind any inaccuracy caused.
Any movement between where you zero and the  measurement position will cause errors.

[Fungus]

Not always practical, but:

You can also wrap the wire around the clamp a few times and get more accuracy that way.

eg. wrap it around 10x and divide the result by 10.

[Martin72]

After measuring, power off and verify that the reading returns to zero.

In this context, I am somewhat surprised that even higher-priced current clamps do not use the compensation method that prevents the core from magnetizing (at least as long as the current clamp is not "overrun").

[Aldo22]

Not always practical, but:

You can also wrap the wire around the clamp a few times and get more accuracy that way.

eg. wrap it around 10x and divide the result by 10.

Thank you, that helps with low currents. 

What bothers me about my ANENG ST212 is that it does not display a stable value.
It constantly changes the measurement display, e.g. in the range from 0.95A to 1.05A, without changing anything in the measurement setup.
These measurements are probably even in the specified range ± (2.5% +8d) for DC current, but difficult to read in this way.
With averaging, the measurement might quite accurate. But the way it is, you have to estimate from the changing values.
But at least it is "honest" and shows you the uncertainty. 

The WinApex 268B seems a bit more stable.

[Phil1977]

If you want to have a look inside:





The cyan clamp housing is glued so I couldn't get a glimpse on the magnetic sensor. The thin green wire going from the main IC blop to the clamp is probably the NCV antenna.
There are two trimming potentiometers - so maybe recalibration of the clamp is feasible.

A small annoyance is that the "ZERO" button only works in DC amps.

[wasedadoc]

A small annoyance is that the "ZERO" button only works in DC amps.

The zero button on any clamp meter is to subtract the ambient magnetic field. Earth's field and nearby magnetised objects. That should be a steady offset. When measuring AC that offset is removed by an AC coupling or software. Have you ever seen a "zero" button on a clamp meter which does not measure direct current?

[mikeselectricstuff]

A small annoyance is that the "ZERO" button only works in DC amps.

The zero button on any clamp meter is to subtract the ambient magnetic field. Earth's field and nearby magnetised objects. That should be a steady offset. When measuring AC that offset is removed by an AC coupling or software. Have you ever seen a "zero" button on a clamp meter which does not measure direct current?

The offset is often done in the analogue domain as offsets can be large compared to the measuring range

[Phil1977]

Yes,

A small annoyance is that the "ZERO" button only works in DC amps.

The zero button on any clamp meter is to subtract the ambient magnetic field. Earth's field and nearby magnetised objects. That should be a steady offset. When measuring AC that offset is removed by an AC coupling or software. Have you ever seen a "zero" button on a clamp meter which does not measure direct current?

The offset is often done in the analogue domain as offsets can be large compared to the measuring range

Yes, thank you, this probably is the reason. But anyhow, the "Zero"-Button is handled by the microcontroller, so it would just have meant a few additional lines of code to make it a "REL"-button in the other ranges.

[thm_w]

Zero button on UT210e works on both DC and AC, for reference.

[Martin72]

Yes, this is simply a REL function.