Review: £10 multimeters - Now includes the new RS-14!

[Murphyv310]

Excellent write up Mark.
Always informative and helpful.

[Crackle]

What a very professional well written and useful review.

Mike

[peter scott]

The Aneng AN8002 (aka Zotek ZT102). About £12 delivered.

This one is very tempting and appears to survive Joe Smith's abuse quite well but the true RMS may be suspect unless it's a one off faulty unit: https://www.youtube.com/watch?v=oNss6h0Zu98
Peter

[Mark Hennessy]

I've done a little bit more testing...

First, the -3dB point of these Aneng meters is 3kHz. That's not stella, but fair enough. The £280 Fluke 179 is similar, IIRC.

Next, the question about true-RMS. I would have been amazed if they'd have lied about that, given how easy it is to test. It's part of the IC, as mentioned earlier, and that IC is used in many other meters at higher price points than this.

However, it's easy enough to test (see attachment). I used my trusty old Wavetek 162 function generator, which can make a wide range of waveforms. My Fluke 8920A is as true-RMS as it gets, being a genuine thermal sensor. I also used my Fluke 87V, just in case. And while I was at it, I included the Bside ADM02, which isn't true-RMS, and gave the expected errors on non-sinusoidal waveforms.

   

In short, all 3 Aneng meters are indeed true-RMS. Even with very narrow pulses (hence high crest factor), the Aneng agreed with the 87V at all times. At the narrowest pulse widths, these two deviated slightly from the 8920A readings, but that's because it can cope with higher crest factors, of course.

This one is very tempting and appears to survive Joe Smith's abuse quite well but the true RMS may be suspect unless it's a one off faulty unit: https://www.youtube.com/watch?v=oNss6h0Zu98

Yes, that's because he tested at too high a frequency (see the YouTube comments), forgetting that the limited bandwidth will attenuate the harmonics and alter the results. For that reason I tested at 100Hz. There's a note in the manuals (except the AN8008, strangely) stating that frequencies above 200Hz won't be accurate. Of course, most multimeters have different tolerances for different frequency ranges - nothing unusual about this one.

The frequency readings rely on the input waveform crossing zero by an amount. This is not uncommon and is unlikely to be a big problem in practice, but the Fluke 87V doesn't have this problem. Stick a capacitor in series if needed!

I also discovered a minor "bug" with the AN8008. When measuring frequency on AC volts, you need a minimum of ~1.7V to get a reliable reading. The AN8002 works down to about 50mV, give or take (1kHz sine wave). Actually, if you use the yellow button to cycle back to AC, then press again to get Hz, you get do a reading for about 3 seconds, then it changes to zero. This works reliably down to about 100mV. I think what's happening here is the meter is changing to a higher range, rendering it less sensitive.

Using the dedicated Hz position is fine - the input sensitivity at 1kHz is about half a volt. That's not as good as the AN8002, which works down to about 20mV (as reported above, but has just been double-checked at 1kHz).

The two meters, despite their visual similarities, are obviously set up differently. The mV ranges are quite different (60mV and 600mV for the AN8002, 9.999mV and 99.99mV for the AN8008). Perhaps that explains the differences?

Either way, the frequency counter is still very usable, and as reported earlier, it has an astonishing response (out to at least 80MHz). The spec suggests 10MHz.

I've tested the current consumption of the AN8008 (I'm sure the other 2 are practically the same). It's just over 1.6mA in most modes, rising to 1.8mA in Ohms (2.7mA when probes are shorted), and falling to 1.2mA in Hz. With such a low current consumption, you wonder why they have an auto-off function! The backlight adds about 5.7mA to the current draw. With the leads shorted and the buzzer sounding in continuity mode, the draw is 15.4mA. The AAA batteries should enjoy a long life. The battery low warning comes on at 2.4 volts and the meter shuts down at 2.1V. During that time, the meter continued to measure 7.5V DC completely accurately. I noticed that if you pressed the yellow button, the meter came back on, showed the low-battery warning, and shut down again. Out of interest, I lowered the supply voltage, and found that it was able to keep doing this until 1.75V.

As suspected, the square wave output is very much dependent on battery voltage. In fact, the peak to peak amplitude is exactly the battery voltage. The rise/fall time is about 1us, and the waveform is free from overshoot and ringing. Because it's AC coupled, you'll get a reasonable amount of "tilt" when driving a load.

I'm sure there's plenty more I could test, but I remain highly impressed with these meters

[peter scott]

Thanks Mark, I've just bought one.

Peter

[Refugee]

I am quite impressed with the AN860B too as it looks better made with longer fuse holders so better for every day use.
The AN8002 is a little more like a reference unit for checking everything else with but at the price the only thing I don't like is the short fuses.

[Mark Hennessy]

Well, Dave Jones has just done a review:

https://www.youtube.com/watch?v=xdGQEVdxmQQ

Overall, he's critical of the lack of obvious safety features (hardly a surprise), but is impressed with the functionality. I don't think he points out anything that I haven't already mentioned here or on the other places I've been posting about it, but the video is still a good summary.

I think he could have placed more emphasised on the functionality for the price. Perhaps that's because he largely ignores the meters at this price point, whereas I've been studying them for a while? In short, before these Aneng/Zotek meters came on the scene, this money would only get you 2000-count meters - certainly not 6000 or 9999-count meters, and definitely not true-RMS.

I also wonder if he's seen Joe Smith's review of the AN8002? That meter seems a lot more robust that appearances would suggest, and I've no reason to suspect the AN8008 will be any different.

Anyway, things have certainly moved on a bit in this end of the market.

Mark

[Murphyv310]

Due to your brilliant report Mark, I'll be ordering one today.
Once again thank you for your time and dedication.

[Nick]

Thanks Mark - I, too, have ordered one - free delivery to Dubai! (but it takes up to a month)

One takeaway from Dave's video was the poor soldering - I'll be re-doing the hand-soldered joints in mine...

[Mark Hennessy]

The soldering on mine was quite reasonable. But having said that, my AN8002 has a few iffy joints. Just cosmetic; nothing that would affect reliability. I guess that goes with the territory.

Noting that the soldering was bad on the 10A shunt in Dave's meter, I'd be cautious about reflowing those, as the calibration could be affected, and the constants are stored in EEPROM. I'm hoping the calibration stays good over time, as I doubt these would be easy to adjust. But having said that, a lot of folk have hacked other meters using that chipset, so perhaps tools will emerge.

I think you'll all be impressed by the size when it arrives