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| UT61E drift and recalibration |
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| Arhammon:
I tested (In 22-33C range) 3 multimeters: 2 Victor with LM385 and UT61E with internal reference. It is same tempco. Video (in russian): https://youtu.be/DhKY4iilgC8 |
| MosherIV:
Hi Just got my UT61E. Wooopie :clap: Measures very accurate at the moment, last digit on UT61E is only 1 count out worst case compare with a TTI1905a against a AD594JN Will have to test again in 1 year to see if there is a bad drift. Temp stability. I notice there are 2 versions of the board The original board has a black plastic cover over the precision resistor divider network. The RevC board (the one I have) has a metal cover over the plastic covered precision resistor divider network. I am waiting for a sunny day so that my conservatory will reach 40C so that I can test for temp stability. I suspect UniT knew they had a problem and added the metal cover to stabilize the temp coefficient. (I suspect the reason why Fluke use a precision resistor divider network on ceramic is because the ceramic is highly temperature stable) |
| MosherIV:
So it was sunny enough yesterday that I put my UT61E in a box in the conservatory for an hour. I also put the other UniT meter (Tenma 72-7755 otherwise known as UT70B) and Keysight U1232a in the box as well. I did a quick check with each meter before putting them in the box. Sadly, this was in the evening and the conservatory was cooling down. The box only reached 30C, not the near 40C I was hoping for So I did not bother moving the TTI1905a and AD594JN voltage standard . I did a quick check by bringing the meters in and just quickly measuring the voltage standard. Both the UniT meters showed a drift with temperature. The Keysight read the same as before. So, sadly the UniT meters do suffer from temperature drift :-- Both UniT slowly drifted back to the readings before I put them in the box, so they do recover. :phew: Just looking at a tear down of the Keysight U1232a, I do not see the ceramic precision resistor divider array, so I wonder how they achieved the temperature stability. I might try wrapping the UT61E precision resistor divider array with insulating polystyrene (my one came wrapped in the stuff) and see if that makes a difference, I doubt it since it is the substrate that need to remain stable. |
| Fungus:
--- Quote from: MosherIV on July 14, 2016, 12:10:36 pm ---Both the UniT meters showed a drift with temperature. --- End quote --- How much? Details, man, details.... |
| MosherIV:
--- Quote ---How much? Details, man, details.... --- End quote --- Sorry, because there was not enough of a temperature differential and it was not conducted scientifically enough, I did not write down the details. The readings were out by a max of 5 counts on the LS digit. It is sunny again today, maybe I will try again tonight or over the weekend |
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