Uni-T UT90D Quick teardown - Page 1
Forum section: electronics / testgear

author: hgg
author_rank: Frequent Contributor
timestamp: January 29, 2015, 01:25:21 pm
content: Hi folks,Just a quick tear-down of the Uni-T UT90D multimeter that I bought for my father.I chose that because it has a very large 3.1" display with easily visible digitsas well as an on screen indication of where to insert the leads for each measurement.The display is perfect at all angles. This is a Uni-T trademark as it seems.I bought it from eud.dx.com (EU Direct) for 33 euros and took a month to receive it in Greece...Its a 4000 counts multimeter.Some specs from the Uni-T website :http://uni-trend.com/UT90D.htmlThe unit is very robust with no cracking sounds when you try to twist it. The red protectivesleeve has to be removed to insert the 9V battery but it can be removed easily.When you open it there are no cables connecting the two case parts which I like. Speakerconnects with two springs and battery with two metal leads.The LCD screen is connected on the board with the awful ribbon connector.I did not remove it...The dial is very stiff and needs quite a lot to pressure to turn it. Quite annoying...It uses two ball bearings on top of two springs. I did cut the first turn of each spring and nowit rotates perfectly with very light pressure and a very positive feel at each selection!Good thing that it does not make any beeps every time you change selection.Some basic input protection.Are these S3G rectifiersThe lead terminals are not bad actually and the test leads plug in very nicely. Not too tight nor loose.Calibration trimmers. VR1 is for DC voltage calibration. It came pretty accurate, a couple of mV off.These trimmers are very dodgy and even the smallest rotation changes the calibration by a largeamount. I don't even know which tool fits in there to turn them...Not good.The button selector for multiple functions is located on the dial itself. Not a bad idea, but itsextremely stiff to press!You can also see the low impedance arrangement. 250V up to 3 seconds.The test leads are the typical stiff Uni-T leads and they have a total length of 110cm.Oxidized tips as usual, but if you clean them with a metal polisher, the continuity testerworks extremely well. They have a resistance of 0.05 Ohms each which is not bad at all.Double ratings on the test leads. CAT III 1000V & CAT IV 600V.Some Measurements:Power consumption for each function(30min auto off)Volts AC: 1356 uAVolts DC & mV: 795 uA. Display Update rate 3 times per second. Pretty fast.Ohm: 831uA Slow measurements.Diode Test : 790uA and 1.49V Does not light a white LED.Capacitance: 672uA Slow.Hz: 752uA You have to insert one lead in the mAuA socket!...uA/mA/A: 1356 uABurden Resistance : A = 0.07 Ohm, mA = 4 Ohm, uA = 103 Ohm.Good for current measurements but UT136C is better.It also has a REL button and a temporary low impedance 400kOhm function.All in all just another typical Chinese multimeter. For the purpose I've bought it, good enough.I am still waiting though for Uni-T to make a better multimeter than the UT61E...Thanks.George.

author: Lightages
author_rank: Unknown
timestamp: January 29, 2015, 06:05:19 pm
content: Be careful with that one. Martin Lorton fieed his UT90C during a review:And Uni-T does make a couple of meters better than the UT61E, at least in some people's opinion. UT139C, UT71D, and possibly the UT171 series and the UT181 series.

author: teslafan
author_rank: Regular Contributor
timestamp: January 29, 2015, 07:48:59 pm
content: Quote from: Lightages on January 29, 2015, 06:05:19 pmTOTALLY AGREE IF THE UT71D COMES WITH 600V FUSES NOW & NOT 250V ONES AS IN PAST?FYI: BUYING A 139c FROM FRANKY TO GO WITH MY uni-t UT139C TODAY.ANY DRIFTING IN TIME OR ANYTHING TO WATCH OUT FOR ON IT?THANKS FOR YOUR VIDEO REVIEW ON THIS MODEL & YOUR ADVICE, APPRECIATE IT.

author: hgg
author_rank: Frequent Contributor
timestamp: January 29, 2015, 09:13:17 pm
content: Quote from: Lightages on January 29, 2015, 06:05:19 pmIndeed, I've seen Martin's video. It definitely cannot measure mains frequency!