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UNI-T UT61E Multimeter teardown photos.

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Wytnucls:

--- Quote from: em132 on April 04, 2013, 09:20:18 am ---
--- Quote from: Wytnucls on April 03, 2013, 11:07:19 am ---Nice job.
--- End quote ---

Thank you.


--- Quote from: Wytnucls on April 03, 2013, 11:07:19 am ---Possibly not much of an improvement
--- End quote ---

Maybe... Maybe not.

With respect, is it any worse than your 71B? How many spark-gaps has yours got?


--- Quote from: Wytnucls on April 03, 2013, 11:07:19 am ---because of trace spacing and general construction
--- End quote ---

Again, with respect, has it been determined with absolute certainty that "trace spacing" was the main factor in downgrading the "GS" models to Cat III 300V / Cat II 600V, and not, perhaps, just it being another simple case of legal "cover-your-ass-itis?"

As for the "general construction," you'd be hard-pressed to find a better solution for isolating the battery (esp. compared with the 71 series!). The 10A fuse is also essentially isolated in its own little corner of the board. The thick plastic input jack "buckets" each act as circular isolation slots, and (to my eyes) the blast protection around the case seems to be well implemented (deep U-groove and thick sidewalls).

Am I missing something?

Not looking to start anything (really!), but a little perspective would be nice.

--- End quote ---
I have a 61E too. Good machine in its price range.
I don't think the 71B I modified offers better protection than yours. It was just a fun thing to do. The only way to tell would be to put them through some high voltage testing, like what the IEC61010 regulations require. For what it's worth, the original 61E didn't survive 2500V on the volt jack, as per Lightages' recent test. The 71 did.
The GS approved UT-61 is a different animal. The few pictures I saw, showed a PCB that was completely reworked to meet specifications.
I use my meters on the bench for low voltage stuff and that's where the 71 excels. I wouldn't recommend it for anything else. If I had to tamper with appliances connected to the mains on a regular basis, I would buy a Fluke for peace of mind.

em132:

--- Quote from: Wytnucls on April 04, 2013, 06:41:02 pm ---The only way to tell would be to put them through some high voltage testing, like what the IEC61010 regulations require
--- End quote ---

Anyone check to see if these new regs require the whole meter to be CAT rated to its lowest common denominator? By that I mean, all (?) the Fluke/Amprobe/etc. meters I've seen don't have any voltage rating printed on the current jacks, only the V-ohms (or a single rating which visibly applies to all the jacks). It's assumed the CAT/voltage rating applies to all jacks equally (rightfully so in the case of Fluke, which all have 1,000V HRC fuses, AFAIK). That's not the case with the "regular" (non-GS) UNI-T's, where the amps voltage rating is stated as significantly lower (250VMAX) than the meter's CAT rating (on the V-Ohm jack), because of the low-voltage fuses used. If these new regs require meters to be max-rated no higher than the fuse voltage, then I can see why the GS UNI-T's had their CAT rating down-rated, even if the voltage input may still technically pass CAT III/1,000V.


--- Quote from: Wytnucls on April 04, 2013, 06:41:02 pm ---For what it's worth, the original 61E didn't survive 2500V on the volt jack, as per Lightages' recent test. The 71 did.
--- End quote ---

Lightages also said "CAT tests do not require that the meter continue to work after the test."

Hi-voltage surges can be unpredictable beasts. You could do 5 of these kinds of tests and end up with different outcomes in each one (from a "still working or not" point of view).

In the end though, if none of them blow up or catch fire, then they pass.


--- Quote from: Wytnucls on April 04, 2013, 06:41:02 pm ---The few pictures I saw, showed a PCB that was completely reworked to meet specifications.
--- End quote ---

Very likely because those pics you saw were of either the "C" or "D" model.

Lightages:
From my interpretation, yes any meter must meet the same CAT rating on all terminals at all settings. The meter cannot have different CAT ratings for different terminals. This is from the most recent CAT requirements but earlier versions allowed it appears. To me, the latest rules make sense because the rules are there for safety when things go wrong. You cannot pick and choose what type of "wrong" happens.

The images that Wytnucls was referring to are from the forums at mjlorton's site:
http://mjlorton.com/forum/index.php?topic=140.msg1052#msg1052

And yes they modified the protection and it still had to be down rated. So I can only assume that the non GS version doesn't even meet the GS specs. Who knows what the real CAT rating of the UT61E normal version is? In this case it is best to keep it for use below 250V and probably no more than CATII.

Monkeh:
They did nothing but fit a GDT and put HRC fuses in. There are no other changes to that meter.

em132:

--- Quote from: Lightages on April 06, 2013, 03:24:16 pm ---From my interpretation, yes any meter must meet the same CAT rating on all terminals at all settings
--- End quote ---

Okay, so that explains why you won't see separate voltage ratings on Fluke's Amp/mAmp/µAmp jacks (unlike the UNI-T's).

But my question still stands: if under the "GS guidelines" the CAT rating must apply to all terminals, then why assume that the 61E's "down-rating" is due to it failing the CAT III/1000V test on the V-Ohm side when in fact it could simply be due to the fuses being rated at only 600V (or 690V as the case may be)?

And unless I'm missing something, Torrentula's 61E has the exact same trace layout as the non-GS version.

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