Author Topic: uCurrent accuracy - what am I missing?  (Read 8761 times)

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Offline SaintGimp

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Re: uCurrent accuracy - what am I missing?
« Reply #25 on: September 09, 2016, 01:13:47 pm »
Oh, I'm sure that your stock is generally fine, but my particular unit definitely has issues.

I scrubbed the flux residue off the board but it made no difference.  Then I desoldered R9 and measured it completely out of circuit - 9.70R.  It is unambiguously busted.  I'm perfectly willing to entertain the idea that I caused it to happen through unintentional abuse, but I don't know what that abuse might have been.  It looks perfectly fine under a microscope.

Anyway, I sorted through a whole bunch of 5% 10R 0805 resistors until I found one that happened to measure exactly 10.0 ohms, soldered that one into the R9 place, and now I get 0.9992 V out for the 1.000 mA DMMCheck current source, which probably means it's just about perfect considering that the UT61E seems to read DCV about 1 mV low anyway.  I'm sure the tempco on this replacement resistor isn't great but it'll do for my purposes, I guess.
 

Offline int2str

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Re: uCurrent accuracy - what am I missing?
« Reply #26 on: October 14, 2016, 09:50:03 am »
Took a while to get to this.

De-soldered R9 and sure enough it was off.
Bought a replacement from Digikey and now it reads much closer on the mA scale.

Still have to replace the other resistors next.

Too bad it came this way :(
 

Offline JDW

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Re: uCurrent accuracy - what am I missing?
« Reply #27 on: March 29, 2017, 09:17:12 pm »
Bought a replacement from Digikey and now it reads much closer on the mA scale.
Still have to replace the other resistors next.
Too bad it came this way :(

I thought all uCurrent's were 100% QC tested prior to shipping.  Or was that done only on the original, non-Gold edition?
 



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