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UNI-T UT61E Multimeter teardown photos.
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stj:
short it with a paperclip, your cable is a recieving antenna - where i live, i power a string of christmas leds dimly with 2m of cable with a cap on the end!!!
joeqsmith:

--- Quote from: honeybadger on March 27, 2019, 01:21:19 pm ---at "mV" DC range it says "OL" when nothing is connected.
at "mV" DC range it measure "0.20mV" even with terminals shorted with thick wire with gold plated banana plugs.
at "V" DC range it masure "0.0020V" with shorted terminals.

edit: accuracy is suppose to be:
220mV +/- (0.1%+5)
2.2V / 22V / 220V +/- (0.1%+2)

So for 220mV range it is suppose to show 0.05mV in worst case scenario -> offset is 400% off.
For 2.2 range it is suppose to show 0.0002 in worst case scenario -> offset is 1000% off.


--- End quote ---

It could be my simpleton math skills ...
I assume it's of full scale, so +270uV?    200uV seems in spec.
For 2.2 the volt range, +2.7mV?  2.0mV seems in spec.

Mine has been modified and may not represent how a stock meter would behave.   With no leads attached, selecting the mV function, it will display OL and slowly drop.   Of the meters I have looked at, this meter was one of the worst for temperature drift.  One of the things I had done was compensate mine.  I would have no way of knowing the tolerance of your 30V supply but I have been tracking the drift.  I have attached today's data.  The voltages are checked against a Fluke 731B reference standard.   The 100ohm is a 0.01% 2ppm Caddock part.   Capacitor is a COG.   

Attached picture shows how badly this meter has been treated. 

honeybadger:
stj: I will try to make a shorting adapter for future use - two gold bananas and few cm of solid copper wire. But how exactly is the "antenna problem" relevant to DC measurements? I mean none of my other multimeters has this "antenna issue" at DC V ranges.

joeqsmith: correct me if I am wrong - when meter accuracy is described as AA% + BBD this means:
"AA" is linearity error from measured value (not from a full range) described as percentage error from measured value
"BB" is a zero offset error described as count of least significant digits at current range at meters resolution.

So when the leads are shorted the linearity error is suppose to be zero and nothing else and only zero offset plays role here -> thus 200uV offset at 220mV range is ridiculously high.


edit: Brymen BM867s is on the way - thank you for your review of 869. I will try to save this sick UT and give it to someone else.

edit2: something else puzzles me. It shows different value when I switch the polarity of the leads. For example 20.35V at one polarity and -20.10V at reverse polarity - both at 20.0V DC.

edit3: my 30V power supply was checked with UT50E (which I know it measures correctly) and when PSU shows "30.00V" and UT50E (connected in paralell to UT61E) shows "30.02V" I am pretty confident it is really close to 30V.
joeqsmith:

--- Quote from: honeybadger on March 31, 2019, 10:52:52 pm ---joeqsmith: correct me if I am wrong - when meter accuracy is described as AA% + BBD this means:
"AA" is linearity error from measured value (not from a full range) described as percentage error from measured value
"BB" is a zero offset error described as count of least significant digits at current range at meters resolution.

--- End quote ---

As I stated, I assumed it was percent of full scale.   It could be percent of reading.  It should be in the manual but I don't always see it defined.   If it is of reading, yours is really out of whack.   
honeybadger:
I guess when it is meant from full range only percentage value is stated - like for an analog meter.

For this DMM it is from reading:


I will confront Bangood with this issue.
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