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DMM problem in DC millivolts range

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Gyro:

--- Quote from: tom66 on July 17, 2023, 01:44:55 pm ---...
For instance connect to 0.5V source and if it reads 500mV on the mV then it is ok.
...

--- End quote ---

In this case (the VC97), the high impedance mV range is 400mV (399.9mV) full scale. Above that it defaults to 10MOhm. The OP confirmed that it reads mV and shorted input zero correctly.

amir.razzaqi:

--- Quote from: Xena E on July 17, 2023, 01:22:27 pm ---If this is a new phenomenon it may be there is some contamination causing the leakage somewhere in or on your instrument, doesn't sound like a big deal though.

--- End quote ---

Thank you for reply
yes, at first the DMM showed numbers bounce approximately 0.5-1.0 millivolts around 0 (I mean fluctuate) but after reading the multimeter's EEPROM (using Arduino) this phenomenon happened.

amir.razzaqi:

--- Quote from: tom66 on July 17, 2023, 01:44:55 pm ---
--- Quote from: amir.razzaqi on July 17, 2023, 11:28:50 am ---Thank you for reply
Does it mean that there is some conflict in this multimeter? Or can it be repaired?

--- End quote ---

There is no fault with the meter if when connected to a known voltage source on mV it reads correctly.

For instance connect to 0.5V source and if it reads 500mV on the mV then it is ok.

I have two multimeters which do this, very normal behaviour due to very high impedance input in mV range.

--- End quote ---

Thank you for reply
But this happened after reading multimeter's EEPROM contents and before that every thing looks good.

dobsonr741:
Did you use a 3.3V level translator for the Arduino when reading the EEPROM? I assume you did it without desoldering.

amir.razzaqi:

--- Quote from: dobsonr741 on July 18, 2023, 09:09:39 am ---Did you use a 3.3V level translator for the Arduino when reading the EEPROM? I assume you did it without desoldering.

--- End quote ---

 Thank you for reply
I didnt use any voltage level translator also I'm in doubt if I use Arduino 5.0V output pin for the first first time as vcc  |O :-// But when I wire up EEPROM and Arduino (in circuit reading) I used Arduino 3.3V output pin as EEPROM's VCC.
The DMM's main chip (DTM1106) working voltage is 2.4~3.6V according it's datasheet.

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