Unit-61E Accuracy

[joeqsmith]

Can you show me some source ? so i can learn about it.

Read through this thread :

https://www.eevblog.com/forum/testgear/ut61e-drift-and-recalibration/
Read through the WHOLE post before asking questions !

Skip past the stuff at the start about the poor drift performance, PedroDaGr8 on reply 12 starts to talk about fitting a replacement 'external' Volt Ref.
They are talking about an early revision board that had the component pads on the PCB, the current revision of the meter no longer has the unpopulated pads   

Look at reply 42 on page 2 - look at the picture of how the through hole Vref is attached to the PCB, and the current limiting resistor.
The original pot needs to be replaced with a higher quality one.

The Chinese site they linked documented the basic mods.  Looks easy enough to do even with the newer PCB.    Looks like $8.00 for the reference.  I did not see where anyone ran a before/after drift test.  I may try it.

[usao]

Ok, entry level question.
I just got the UT-61E (mainly because of the 22,000 counts).
Never had a meter better than a Harbor Freight special before.
Interested in checking accuracy now that I have so many counts.
Specs say resistance in the medium resistance range is 0.5% (I think it's something like up to 200K or so).
If I get a Vishay 0.01% resistor in that ohm range that should be accurate to the last digit the meter can display, so it would tell me the total error (number of digits) off the meter is compared to the resistor, is that correct?
So, a 100K @ 0.01% resistor is going to be between 99,990-100,010 ohms, correct?
The meter cant display anything greater than 0.5% accuracy (99,500-100,500 ohms)?

[Fungus]

So, a 100K @ 0.01% resistor is going to be between 99,990-100,010 ohms, correct?

Correct.

The meter cant display anything greater than 0.5% accuracy (99,500-100,500 ohms)?

The specification is actually "0.5%+10" so you have to add/subtract 10 to those numbers.

Result: 99,490-100,510 ohms

But ... notice that the meter is "22,000" counts, ie. it can't display "99,490" on screen.

When you measure your resistor it will select a range from 0 to 220,000 Ohms and will display a number in the range 99.49k to 100,51k ohms.

A 200k resistor would be a better choice because the upper/lower values of error will both show 5 digits on screen.