Products > Test Equipment
UT61E drift and recalibration
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stephenlm324:

--- Quote from: Nuno_pt on December 23, 2013, 05:55:43 pm ---Hi,
Has anyone play with the CW1,2,3 pots?

--- End quote ---
These trimmers are for AC voltage, to improve linearity at high frequency, so I'm not going to touch them.
Nuno_pt:
Hi stephenlm324,

I see that you did Chinese external Vref mod and replace the VR1 2k trimpot with two resistors and an 50Ohm trimpot, as this mod improve the calibration and stability?

Did you use an 50Ohm precision pot and what values do you use on the resistors ?

Did anyone gather any new info about calibrating the resistance side, maybe replacing R34 and the others with more precise ones?
     

I just saw this mod on the mjlorton forum for adding a bunch of new functions using the yellow and blue buttons, see the link ( http://mjlorton.com/forum/index.php?topic=285.0 )
and the YouTube video, would this be worth the trouble?
cuban8:
My UT61E (~3 years old) came with an "out-of-the-box" modification: An LM385 (TO92) and a series resistor  :wtf:
No idea why, maybe the internal reference was faulty and somebody decided to"salvage" the meter by slapping another reference on...
Looking at the specs for the LM385 this is not really an upgrade though.
Wytnucls:
Gosh, what a mess. Where did you buy that lemon?
cuban8:
German distributor, wasn't even from ebay.
Performance-wise the LM385 is probably not too far away from the reference in the Cyrustek chip (Cyrustek lists 75ppm/°C typ, LM385 is 150ppm/°C max. for the standard grade, so typical drift, while not stated, is likely similar). Measured against my 10V reference, it has drifted ca. 5mV since I got it, which is not too bad.
I'm not impressed with the soldering though.
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