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UYIGAO UA4070L LCR meter review and tear-down

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Wytnucls:


I bought this cheap ($25.00) Chinese LCR meter while browsing around Jalan Pasar in Kuala Lumpur, a couple of months ago.
It is made by UYIGAO (Shenzhen Electronic Technology company) http://www.uyigao.net/en/main.asp
It is a small (176g) 2000 count meter, reasonably sturdy, with a removeable holster, which I primarily bought for the inductance range.
It doesn't measure ESR or anything else, apart from capacitance, resistance and the usual PNP/NPN transistor hFE.
Accuracy is fair for such a cheap meter, but not much of an improvement, compared to a decent DMM, on the resistance and capacitance ranges. The inductance measurement on the other hand, is surprisingly accurate and thus useful.
It has a power On/Off button, a hold function and a bright backlight, which fades after 7 seconds.
The bale is adequate, holding the meter at 45 degrees, but is not very stable when the range switch is moved.
The range rotary switch is rather small, but functional, with a firm position detent. There is no autoranging mode.
The LCD screen is very good, with large fonts for any measurement, but nothing else can be displayed, apart from the low battery icon.
It is powered by a 9V battery, with direct contact to metal inserts in the compartment. The lid is secured by a screw with a metal receiver in the enclosure.
It comes with some small but sharp probes on short unmarked leads (100cm).
There a 3 jacks marked:     LC-    LC+/COM      Ohms
The LC side is fused for 200mA and there is a 36VDC restriction on the Ohm side.
It supposedly complies with IEC1010 regulations.
Here are the dimensions: 143x74x35mm.
There is also an auto power-off function on the meter, as written on the front plate.
The little booklet that comes with the meter is written in simplified Chinese only.
There is no 'Relative' mode though, so the resistance of the leads has to be substracted mentally from the readings for low resistance measurement.

Here are the specs:

Resistance
20 Ohm 1.2%+30
200 -200K Ohm 1%+20
2M Ohm 2%+20
20M Ohm 2%+25
200M Ohm 5%+25
2G Ohm 10%+35

Capacitance
2nF 2.5%+30
20/200nF 2.5%+25
2/20uF 2.5%+30
200uF 7%+50

Inductance
20mH-20H 2.5%+25  measured at 150 Hz

hFE 10-1000 10uA 2.8V Vce
NPN/PNP

Wytnucls:
The case is held in place by 2 self-tapping screws, revealing the PCB, connected to the battery holder by 2 wires.
The red rubber/plastic holster has to be removed, before dismantling the meter.
Avoid taking the meter apart any further if you don't have to, because she's rather difficult to put back together afterwards.
The LCD has a LED and a large diffuser, which are hard-wired to the PCB.
The range switch sits on 2 springs capped by 2 little metal balls, falling into grooves, molded in the bodywork.
Careful you don't lose the springs or the little balls during separation!

Adjustment pots can be tweaked to achieve higher accuracy, mostly for capacitance measurement.
1. VR1 L 20 mH
2. VR4 C 2000pF
3. VR2 C 2uF
4. VR3 C 200uF

Low battery warning
PTC MOV 250V

Here is some data concerning capacitance measurement on all ranges. I added UT71D and UT61E readings for comparison.

Capacitor  UA4070      UT71D       UT61E
100uF         95.1         96.40        95.35
47uF           47.6         44.26        44.12
10uF           9.39         9.885        9.876
1uF           1.033        1.0432      1.0346
0.47uF      0.403        0.4103      0.4054
154nF       151.9        147.89      148.57
15.3nF      15.32        14.939      14.978
471pF          492            490           538
221pF          231            235           288
56pF             62              65           116

Wytnucls:
According to the booklet, the waveforms used by the meter for inductance and capacitance measurements are meant to be at 100Hz, but I measured them at 150Hz on the oscilloscope.
Electrolytic capacitor datasheets usually quote capacitance measured at 120Hz +/- 20%.
I don't know why there should be a difference in waveform, but the meter uses a square wave for inductance and a triangular wave for capacitance measurements.
The triangular wave is probably just the capacitor charging and discharging.

I don't see any for sale on eBay, but the meter should be on Alibaba's site or any other Chinese online sellers.
http://detail.china.alibaba.com/offer/948046658.html (16.00 US$)
I found this one (UA6243) for 18$ : http://www.escitec.com/digital-lcr-multimeter-ua6243l-19-ranges/
Not sure if there are any differences. I think this one may have a continuity buzzer.

Bored@Work:
Funny how they try to mimic the general Uni-T look.

Wytnucls:
Yes, it does look a bit like a UNI-T creation, down to the red logo.  :)
The box is also very similar.
There may be a connection between the two companies. Who knows...

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