Products > Test Equipment
UNI-T UT61E Multimeter teardown photos.
Wytnucls:
It could have failed either tests or both for the CAT III 1000V rating. (Destructive pulsed 8000V arcing on the volt/ohm ranges and/or 2000V arcing on the amp ranges).
In the end, UNI-T chose to apply for a CAT II 600V CAT III 300V listing, with pulsed 4000V and 1200V testing with the required 600V HRC fuses.
And yes, the first GS 61 I saw was probably a C/D model with a different layout.
On the GS61E, the bottom part of the PCB I looked at recently, is similar to the older version, except perhaps for beefier PTCs. I don't know if the traces have the same copper thickness.
Lightages:
--- Quote from: em132 on April 06, 2013, 03:51:46 pm ---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)?
--- End quote ---
They added bigger PTCs, a spark gap that wasn't there before, 600V rated fuses, and it still was rated lower than the original. The original model has only 250V rated fuses and poorer input protection so it cannot be rated at 600V, only 250V. The CATII is a safety margin over what the GS is rated because the original has less input protection. Simple logic.
But the main thing is to realize that the UT61E's original safety ratings are an outright lie and should not be trusted. We can only guess what its true CAT rating is.
Wytnucls:
The original PTC is a MWZ11 75HV made by Sinochip. I couldn't find the exact reference, but I think it has a resistance of 1.1K Ohm, a withstanding voltage of about 900V, max current of 300 mA and a switching temperature of 75c.
http://www.sinochip.net/eng/wmz11a.pdf
metRo_:
There are any cheap case for this DMM that I can buy at ebay? Thanks :)
ACvolts:
--- Quote from: tekfan on May 11, 2011, 08:30:08 pm ---The input protection circuitry looks a bit whimpy but other than that the build quality looks excellent. I like how they didn't use just one of those ICs covered in a blob of plastic. The red board is also a special touch (getting quite tired of all the green ones).
It looks like you've got a really decent meter.
--- End quote ---
Dude!.. ahhhh, I think that's orange, not red. :P :-DMM
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