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UT61E drift and recalibration

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Nuno_pt:
It was better to remove that mode and do de Chinese external Verf mod witch is 5ppm/C°.
Stephenlm324 have done that mod and also replace the VR1 pot with two resistors and an 50Ohm pot, and claims better stability and accuracy, see on page 2 post

I've a friend that works here in a factory that makes all kind of resistors, including precision and I'll ask him if he can bring me some precision resistors better than 0.01% 10ppm/C°, and I want to see if I can get my hands on some silver mica caps with ~1% 50ppm/C° to measure on all the DMM ranges and try to adjust capacitance with the VR3 pot (Since from what I can see it's the only thing that will affect capacitance, I'm I wrong on this?)
 

cuban8:
Yeah, doing the LT1790 mod would definitely improve things. I'll try to get hold of one of those.

iloveelectronics:
That Chinese mod looks very interesting and simple to implement, I think I will give it a go myself! Ordering the parts now...

Nuno_pt:
Franky,

The Chinese mod (Vref) is no big deal, like change the VR1 pot with 2 resistors and a 50 Ohm pot, for better stability and accuracy on the Vdc.

I'm thinking to make the mod to add more functions, list on the mjlorton forum.

Add:

Backlight for 60s
Auto power after 15min function (ON/OFF)
RS232 port (ON/OFF)
MAX/MIN / MAXMIN

See the link ( http://mjlorton.com/forum/index.php?topic=285.0 )

Franky u got PM.

cuban8:
Looking at the schematic, there is no need for using two resistors when changing the VR1 pot; VR1 is used as a rheostat (variable resistor) in series with R16, not as a voltage divider. Therefore, you can reduce VR1 and increase R16 (or add another series resistor).

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