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| Uni-T UT120C review and tear down |
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| Wytnucls:
I just bought this cute mini DMM in Hong Kong for 105 HK$ or about 13.50 US$. I had wanted to buy it before but couldn't find it anywhere. The meter is sold sealed in a plastic blister with a small operating manual written in simplified Chinese and a warranty card. The UT120 range consists of three models, the 120C being top of the line, with current measurement (uA/mA only) and a 400mV scale. The UT120A model doesn't have the capacitance function, otherwise it is identical to the 120B model. The meter has reasonable specs for something this cheap: 4000 count, auto-ranging, auto shutdown (after 30 minutes), V/mV/mA/uA (DC/AC), Ohms, Diode, Caps, Continuity, Hz and duty cycle (%). It also has a relative mode and the usual data hold function. It is well made, with a sturdy case and very legible LCD screen (no backlight). It runs off a 3V CR2032 battery and has a low battery warning icon that comes on at 2.4V. It is fitted with small, permanently attached probes, which are quite adequate and rated, like the meter, CAT II 600V. The leads are PVC, marked 24AWG and they feel a bit stiff compared to the usual silicone ones. The function selector rotary switch has some unwanted friction, but it can still be turned with just one finger. It is sold in a see-through case, with some removable plastic film protection on the black part of the face plate, which I only noticed after wondering for a few minutes why the screen was so washed out! ::) Here are the specs: DCV 400mV/4V/40V/600V ±(0.8%+3) ACV 4V/40V/400V/600V ±(1.2%+3) DCA 400uA/4mA/40mA/400mA ±(1.0%+3) ACA 400uA/4mA/40mA/400mA ±(1.5%+5) Ohms 400/4K/40K/400K/4M/40M ±(1%+2) Caps 4n/40n/400n/4uF/40uF/100uF ±(4%+3) Freq 10Hz~100KHz ±(0.5%+3) (>30VRMS between 10kHz and 100 kHz) Duty Cycle 0.1%~99.9% ±(0.1%) Impedance <10MOhms The continuity buzzer is not latched, but quite responsive, although a bit scratchy. Diode test open voltage is 1.44V, so won't light up any LEDs or display the voltage drop. Some people might appreciate that the meter doesn't beep when the range switch is moved to another mode. It is definitely pocket size at 76 grams and here are the dimensions:110mm X 58.2mm X 10.8mm |
| Wytnucls:
Here are some pictures of the inside, which show a well laid out PCB with mostly SMD parts and with few glaring issues, in my opinion. There is only one screw, which fits into a receiving metal insert, holding the back in place, after it has snapped in its position. There are no screws on the PCB, it fits in a slot at the top of the case and is held in place by plastic clips, which are part of the case. It has a 400mA fuse for the mA range and a PTC on the other functions, for input protection. It is a self recovery 250V 400mA fuse overcurrent protector (WH250 400): http://en.b2b168.com/s168-29888660.html PPTC (Polymeric PTC, Polyswitch) http://en.wikipedia.org/wiki/Resettable_fuse As you can see, the piezo speaker is sitting just behind the LCD screen, which may explain why the sound is rather faint. I will test its accuracy against my other meters, when I get home. This particular meter came from China, left the factory on 20th Nov 2012 and carries a China warranty only, valid for 1 year. The PCB is quite barren, understandably, with most functions accomplished by U2, the DMM ADC, which is hiding under a blob of black epoxy. There are no voltage regulators, the ADC works directly off the 3V battery. The cruciform battery holder looks a bit crude, but it does the job. 4 trim pots can be found: VR1: DC Volt adjustment VR2: AC Volt adjustment VR3: Capacitance adjustment VR4: DC mA adjustment The burden voltage on the mA range is 3.45mV/mA and 102uV/uA on the uA range, which is pretty good compared to the UT71D (5.33mV/mA and 500uV/uA). For reference the Fluke 87V has a burden voltage of 1.80mV/mA on the mA range and 102uV/uA on the uA range. The resistances involved include the current shunt, the polyswitch and the leads (3.45 Ohms on mA and 102 Ohms on uA) The see-through plastic protective case is a bit bulky, but it shields the meter quite well. One feature I hadn't noticed, is that the meter can be used with the translucent case closed. There is a clear aperture over the LCD screen and 2 openings in the case for the probe leads to pass through. So, once the proper selection has been made with the range switch, the case can be closed and the meter can be used in a rough and dirty environment, without having to worry about contamination. It is kind of rainproof, but certainly not waterproof. |
| SeanB:
Interesting little unit there, quite compact and a nice little emergency unit. Where do you call home? |
| Wytnucls:
Home? mmm....right now: Mauritius, Jo'burg and Belgium. ;) |
| Lightages:
That looks like a nice step up from the UT10A. I am interested to hear about the accuracy. The fuse is a self resetting fuse? |
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