Products > Test Equipment
UT61E drift and recalibration
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Nuno_pt:
See the comments from stephenlm324 on the previous pages, he switch with one of 50Ohm, and a network of two resistors.

The more course the pot (Ohm) more drift it will have, most have 1%, it's more drift on 200Ohm that on 100 or 50Ohm.
don.r:
As I understand it, its not the drift on VR1 that is the issue but more the vibration sensitivity which seems pretty constant across all these pots at around 1%. So instead of 20R of change we get 2R for a 200R pot or 0.5R for a 50R pot. My question to Stephen, I guess, is why 50R and not another value?
mcinque:
Maybe the complete schematics could be useful to find what exactly what that VR does. Hope it helps.
Found on http://www.frankshospitalworkshop.com/electronics/diy-voltage_reference.html
don.r:

--- Quote from: Lightages on January 01, 2014, 05:37:31 pm ---I am curious. What are the costs for the external ref mod and the other parts? It seems to me that this is turning a relatively inexpensive meter into something more expensive and then also needs to be recalibrated after the mods to be of any use. Is it worth it? If it is just for the fun of it then yes of course it is worth it but as far as being of real value?

--- End quote ---

As no one has replied to this yet and I am in the process of applying several of the mods here is the cost.

LT1790ACS-1.25 - $5 (I got two for that price but that is the going rate)
caps/res - 10c total
NTC thermistor - 20c (10 for $2)
200ohm (or 50ohm) genuine Bourns pot - $2. (Chinese knockoff - 50c)

So all together less than $10... probably a lot less if you check your junk box or shop around.
Lightages:
Hmmmm, so now the "bargain" UT61E goes from being a $60 meter to being a $70 meter, and still no proof of long term drift benefit, has very poor input protection, and needs to be re-calibrated. Don't forget the time to do the mod in the equation. I am not so sure I would recommend this meter anymore. I hope those who have taken the time to do this actually benefit from it. If you want the benefit to last a while, I would look at adding the input protection too. It won't necessarily make it safer for you but might prevent the meter from dying prematurely.
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