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Products => Test Equipment => Topic started by: aparlett on February 28, 2013, 07:07:08 am

Title: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: aparlett on February 28, 2013, 07:07:08 am
Hey guys

was wondering if any of you guys heard of the UNIT-T U233 meter.
Here is the link to the eBay seller
http://www.ebay.com.au/itm/271031598957?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 (http://www.ebay.com.au/itm/271031598957?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
I got the guy to send me pictures of the inside and it looks to have no protection circuitry.
(http://imageshack.us/a/img849/7733/p1070812oa.jpg)


what do you guys think?
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: Wytnucls on February 28, 2013, 07:20:58 am
Nice 10,000 count AC only clamp meter with auto calibration.
Fair price for this one, with datalogging (99), USB, Backlight, lots of phase tests and power/energy display.
No bar graph, but multiple display.
It only does voltage, so input protection is not really necessary. Probably has crowbar circuit for its 600V rating.
The PCB looks fine, with just some flux residue in some places.
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: BravoV on February 28, 2013, 07:21:23 am
Clamp meter measures current using magnetic field thru the clamp, and totally electrically isolated, hence no need for heavy protection circuitry like big HRC fuses as ordinary multimeter for current measurement if this is what you're looking for or expecting.

For measuring voltage, ohm, temperature and etc don't need those big fuses.

Edit : Wytnucls beats me ...  :P
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: Lightages on February 28, 2013, 07:21:50 am
Looks like junk to me. Solder blobs hanging around on the board everywhere, no input protection, I see one tombstoned diode, and melted plastic on some ICs where it looks like some ham fisted monkey was in there with a soldering iron trying to fix things. Don't buy it.

P.S. And yes you still need some input protection......

P.P.S. A 3 phase meter only good to CATIII 600V and CATIV 300V? This somewhat limits its usefulness in real world 3 phase power measurements, even if it really meets its CAT ratings.
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: aparlett on February 28, 2013, 07:38:51 am
Yeah the input jacks look pretty poor quality, and lack of protection for over voltage is a bit of a worry. Been looking around and there is not much else on offer unless you spend alot more. Extech used to have one but cant get a hold of that one anymore :(
Its for Uni to use in LAB so not dealing with anything too exstream, just want something reliable
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: Wytnucls on February 28, 2013, 08:56:52 am

P.P.S. A 3 phase meter only good to CATIII 600V and CATIV 300V? This somewhat limits its usefulness in real world 3 phase power measurements, even if it really meets its CAT ratings.
Why do you think it limits its usefulness? It has 3 voltage inputs for all phases. It does single phase 2 wires, 3 phase 3 and 4 wires.
There is never more than 230 volt on one input jack.
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: Lightages on February 28, 2013, 09:07:32 am
Let me rephrase that. For a meter that is implied to be used for high energy and power work, its limits on its CAT ratings are in contradiction to its implied use. Not that I would trust ANY Uni-T for anything more than in the home use away from the distribution box.
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: SLJ on February 28, 2013, 01:44:06 pm
What the hell is this crap?  :--

(http://www.stevenjohnson.com/web-pics/UT233-board.jpg)
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: aparlett on February 28, 2013, 02:33:57 pm
What the hell is this crap?  :--

that makes me worry I really want a 3 phase meter, but the quailty of the uni-T meter is not looking good at all  :-//
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: Wytnucls on March 02, 2013, 02:51:10 am
Probably just some flux residue and jpeg artifacts. Pictures are not always worth a thousand words.
In my experience of taking pictures of PCBs, flux residue always looks worse than the real thing, even without flash.
Ask him for a close-up shot, if you're still interested.
And by the way, the meter has got input protection, in the form of a current limiting resistor on each phase input, just like the new Fluke remote voltmeter.
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: aparlett on March 02, 2013, 03:02:44 am
I sent him an email to take a few close up shots.
If not there is an the EXTECH 380976 SINGLE/THREE PHASE 1000A AC POWER CLAMP METER from trio smart cal for an extra $70 works with 3 phase but only one voltage input. so ahve to swqap the meter around.
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: Wytnucls on March 02, 2013, 03:31:40 am
Extech probably has the worse reputation here, when it comes to the quality control of their PCBs.
I have yet to see a badly put together recent UNI-T meter.
This UNI-T clamp meter even has proper PCB wire connectors, whereas some manufacturers would have soldered directly to the PCB.
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: amyk on March 02, 2013, 05:36:26 am
I say it's definitely flux residue.

The IC packages will not melt under the heat of soldering, and for good reason. They're made of thermosetting resin and not thermoplastic.

Can't find that tombstoned diode...  where is it?
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: Wytnucls on March 02, 2013, 06:21:44 am
Can't find it either and I don't see solder blobs anywhere. I think Lightages was a little hasty and shooting from the hip this time.  ;)
The picture is not of the best quality. High res shots should resolve all that.
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: aparlett on March 02, 2013, 01:11:10 pm
Might just go for Uni-T take a plunge its an Australia seller. so hopefully should be ok
Title: Re: UNI-T TRUE RMS DIGITAL LCD CLAMP METER UT233 3 Phase
Post by: Lightages on March 02, 2013, 02:34:42 pm
Yeah I goofed on the diode. It looked like it but when I look again it is fine, no tombstone. It is funny how your eye can get fooled, especially when there is some bias involved. Yes, I am biased against Uni-T, I admit it. The solder blobs are all over the place, and there are even a couple that look like they could be shorting or very close to shorting across traces.

The first bad thing is that the resistors from the input posts resistors are just held in with big blobs of solder. They do not appear to be mechanically fixed in place, just held with solder and lots of it. The crimps on those ring terminals should have been crimped onto the leads first before the solder was applied. Another obvious mess is right beside the ground jack where there is a line of solder or a piece of excess wire going from one solder pad to a via beside R76. In the circular cropped image provided by  SLJ you can see another solder bridge going from D20 to the IC beside it. And then there are all those messy rework solder blobs in that same image.

Really guys, this is a meter meant to be used on high energy circuits and things like this inside do not give me any level of confidence that it would be safe to use. I have my opinion, that's all.