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David and Goliath ( small DMM testing story )

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Kiriakos-GR:
This afternoon, I had the idea to perform some quick tests on my little UNI-T UT30D,
before I put it back to my tool box.

I did test all the Oms ranges , DC /AC/ volts, and then tested it about accuracy at mV & uA .

Very interesting results the list that I can say for a small DMM build at 30/11/1998  :) 

Enjoy the pictures..   :)

Vertigo:
kewl :)
i get the impression that uni-t makes pretty decent meters, but on some models
try to cram in too much functionality at to low a price which undermines their performance.
making it kind of a hit and miss brand, with some questionable models (like the one dave reviewed)
and some high value for low budget in each series.

i just ordered 2 of them myself; the 61E and 33C.

Kiriakos-GR:
From my observations about accuracy, that comes after testing old gear ( digital and analog ) VS the modern expensive one models.
The conclusion are that any well made old gear, it can handle nicely the Ohms law and the variations of it,
about Amperes or Volts.

Allot of complexity added in the new gear, with the addition of circuitry's like:
True RMS on AC / Frequency counters / Min-Max-Average/  Temperature / db /  etc etc

All those functions demands, additional electronics that they should coming with,
lots of speed and accuracy, so to be called as acceptable.

What made me to test this little DMM, was the fact that now I own one enormous amount of hand-held DMM,
and I wanted to test it, so to make my mind if I will put it back on my ( travel light) toolbox,
or send it for recycling.
After all this tests, I got surprised of how well it responds even today,
and I am going to keep it.
Its stamped as CAT I 600V, and for such tasks its good to go. 
If I do anything wild with it, like using it in other CAT higher categories,
I will had to blame my self, and not the DMM.

Another interesting observation, is that the PCB on the range switch,
its still like new, no signs of wear at the contacts or any damage.  :)
( I got it back at 2000, and so it is active for almost 11 years,
but I do not remember the price that I payed for it)

saturation:
One thing an expensive DMM has is IEC and MILSPEC environmental ratings.  To show its stuff, you have to put the meter to its extremes.  That would be the equivalent of taking the DMM on a hot summer or a cold winter day, and do some measurements.  Your DMM should not drift out of spec for such exposure; just put the DMM in a refrigerator for an hour, which is typically in the 40F, and recheck the accuracy.  It will also cause a lot of condensation on the DMM, which is expected if you take a DMM from outdoors in winter to indoors after your work is done; if the meter still runs well, that's what you pay extra for.  If it works in cold, chances are it will work well to the other end, in heat, as components are temperature compensated and the casing is environmentally robust for such changes.



--- Quote from: Vertigo on July 03, 2011, 09:39:07 am ---kewl :)
i get the impression that uni-t makes pretty decent meters, but on some models
try to cram in too much functionality at to low a price which undermines their performance.
making it kind of a hit and miss brand, with some questionable models (like the one dave reviewed)
and some high value for low budget in each series.

i just ordered 2 of them myself; the 61E and 33C.



--- End quote ---

Kiriakos-GR:
I do not think that my story had anything in common with this wacko in Iraq  (PDF attachment) ,
even so, some one likes to believe that because of him.
Fluke came to the point to build the 87V and 28II, as capable to withstand in conditions where the Fluke 87III was failing to operate.

But this example of an electrician, represents the needs of the less than the 1% or better, the 1 in 1.000.000 of the electricians out there.
For everything it worth's, I would say that personally, I refuse to turn the exception in to a rule.



 

 

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