EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: DW1961 on November 05, 2021, 06:29:26 pm
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I didn't find any reviews of this with a few cursory searches here at EEV or on Youtube/Web. An Amazon reviewer said the voltage and amperage was dead on compared to his Fluke, but he didn't give details. Looks like it has decent protection for a cheap meter, for low voltage use anyway.
I also have an Amazon 2000 count 15.00 model that people here said is a rebranded CEM. It's not auto ranging, but it's outward built quality feel more solid than the UNI-T.
Product Description $30.00 on Amazon:
UNI-T Digital Multimeter Tester UT133A, AC DC Voltage Current Dmm Multimeter 6000 Counts Auto Ranging NCV Measures Volt Amp Ohm Capacitance Frequency Temperature, Continuity Diode Test, Palm Size
Link: https://www.uni-trend.com/html/product/General_Meters/Digital_Multimeters/UT133_Series/UT133A.html (https://www.uni-trend.com/html/product/General_Meters/Digital_Multimeters/UT133_Series/UT133A.html)
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It looks like a decent DMM for that price, but I don't think this is a new model. I did a search on this forum and found 2 references to model UT133A:
- The model was mentioned here (https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg2316606/#msg2316606) in April 2019.
- And here (https://www.eevblog.com/forum/projects/hacking-a-surprisingly-good-uni-t-multimeter-teardown-and-serial-com-upgrade/msg3089483/#msg3089483) is another teardown of model UT133A. The PCB in that teardown seems to be an older revision (date code 1816) than the PCB in your meter (date code 2113).
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It looks like a decent DMM for that price, but I don't think this is a new model. I did a search on this forum and found 2 references to model UT133A:
- The model was mentioned here (https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg2316606/#msg2316606) in April 2019.
- And here (https://www.eevblog.com/forum/projects/hacking-a-surprisingly-good-uni-t-multimeter-teardown-and-serial-com-upgrade/msg3089483/#msg3089483) is another teardown of model UT133A. The PCB in that teardown seems to be an older revision (date code 1816) than the PCB in your meter (date code 2113).
Must be the updated version. It feels cheaper on the outside than my $15.00 amazon CEM rebrand. It's lighter and the selector feels a lot thinner and overall the case seems more hollow than the 15.00 Amazon MM. I think at one point I actually tore the Amazon thingie down, but can't remember if it actually used both PTC and MOVs. I always end up going back to the Amazon DMM for DC work. It's only 2000 count but good enough for my needs. It's more compact, feels right and has very positive controls.
I have a UNI-T Clamp meter that I tossed up here awhile back and seemed pretty decent. So, I wanted a UNI-T DMM to go with it.
I'm going to test a new bench power supply I got (cheap Chinese model) and compare the amperage to the supply read out. I'm not unhappy with the 133A, but it's just meh, really.
Also, the NCV doesn't work for shit. Very inconsistent. I'll test that again, but when I first tested it, it was shit.
PS-Just had a look at the old 133A. Check out the logic processor. It uses a blob controller. The new one is actually a solid case chip. It's an SDIC 7501 model: Hangzhou SDIC.
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Just noticed those are 600V fuses, not your standard CATIII 600V rating with 250V fuses.
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Specs. here --> https://www.uni-trend.com/meters/html/product/General_Meters/DigitalMultimeters/UT133_Series/UT133A.html (https://www.uni-trend.com/meters/html/product/General_Meters/DigitalMultimeters/UT133_Series/UT133A.html)
Flyer here --> https://www.uni-trend.com/uploadfile/2018/1223/20181223110016140.pdf (https://www.uni-trend.com/uploadfile/2018/1223/20181223110016140.pdf)
$21.64 direct from Uni-T, including shipping. Sometimes the Chinese versions are not the same as the ones built for EU/UK.
https://www.aliexpress.com/item/1005003022741292.html (https://www.aliexpress.com/item/1005003022741292.html)
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Specs. here --> https://www.uni-trend.com/meters/html/product/General_Meters/DigitalMultimeters/UT133_Series/UT133A.html (https://www.uni-trend.com/meters/html/product/General_Meters/DigitalMultimeters/UT133_Series/UT133A.html)
Flyer here --> https://www.uni-trend.com/uploadfile/2018/1223/20181223110016140.pdf (https://www.uni-trend.com/uploadfile/2018/1223/20181223110016140.pdf)
$21.64 direct from Uni-T, including shipping. Sometimes the Chinese versions are not the same as the ones built for EU/UK.
https://www.aliexpress.com/item/1005003022741292.html (https://www.aliexpress.com/item/1005003022741292.html)
Sadly, they are never the same in any market. Inwardly, it seems pretty solid. It's fast. Ohm readings take about 3-4 seconds, but everything else is fast and immediate. My 15 dollar Amazon CEM clone feels better on the outside. The Amazon DMM I have is only 2000 count though and auto nothing, not a big deal. The UNI-T is not a bad unit. I wish I had a Fluke to compare reading with, but from the reviews I've seen, even cheap MMs are pretty accurate overall. The real test is in in milli- area though. I hooked it up to my power supply last night and the amps on the supply read 2.888 and the UNI-T read 2.888 so there's that.
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Milliamp reading For what it's worth:
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I got some mixed impressions:
The selector switch feels good. The update rate is reasonable. The ohms auto-ranging is a bit slow due to many ranges.
The continuity beeper however is slow, something like a few 1/10 of a seconds delay :--, it is not really bad, but definitely a weak point.
The µA range shows some 95 ohms, so reasonable low burden there. However the mA range shows some 1.9 Ohm (may include a bit from the probes) and this is not good, with a high burden at 600 mA. I somewhat doubt that there would be extra range switching with more than 60 mA.
There is no way, at least I have not found one to keep it in a fixed range. So it is auto range only.
Input impedance is more like 11 M in the V range and 10 M in the mV range.
The AC measurement is low bandwith: 5 kHz is already some 50% down from 100 Hz and allread 500 Hz reads some 2.5% lower than 100 Hz
(I doubt my generator is that bad). At least it has low voltage AC (600 mV range) - not all lower cost meters have.
The AC mV range seems to not like a DC offset: some 1.4 V DC cause the 600 mV AC range to show OL. Still the reading is like AC coupled, so the AC RMS part only.
The mV range seems to work fine also to low voltages (e.g. 5 mV still look OK). The AC V range seems to start at some 10 mV.
It is still a good meter in the low price range.
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I had a quick look at the AC response for different frequencies. The data are for some 150 mV in the mV AC range, with the signal from an old function genrator. The main point is the rather steep drop with a -3dB point at some 4.3 kHz and -6 dB at 5 kHz and essentially 0 at 15 kHz.
The very steep drop and also the fast (essentially instant) settling of the reading in the AC ranges suggests that the meter uses something like digital RMS for the AC ranges. The response is a bit different from a simple sin(x) / x and thus likely a non uniform sampling.
The burden voltage in the µA range is not that great - the ranges are 600 µA (Still OK) and 6000 µA with a 600 mV max burden.