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Calibration of an ANENG AN870

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coromonadalix:
something like this ?

https://www.eevblog.com/forum/testgear/cheap-aneng-meter-calibrationreset-procedure/

http://www.kerrywong.com/2016/03/19/hacking-dtm0660l-based-multimeters/

https://www.eevblog.com/forum/testgear/the-official-an8008-meterthread/

youll have to sniff the eeprom and decypher it to get the cal constants  or use some of the links methods ??

Fungus:

--- Quote from: fant on October 25, 2020, 04:37:11 pm ---And only one guy (that I thanks) helped me, the others just used bits to move air.

--- End quote ---

Moving air is the real problem. Even if you calibrate it it might be wrong in a few hours because the sun changed position and temperature changed by one degree.

So... before you even attempt to adjust this meter, it's a good idea to find out how much it's affected by temperature. ie. put it in the fridge for a while. Put it in a warm place for a while. See how much it changes.

After that you'll need to find a small EEPROM inside it that holds calibration data for each range and figure out how to read/modify it.

Trader:
Sorry about my naive question, I know the way to calibrate those DMMs is through the EEPROM, but since they use the ICL8069 voltage reference, why not discover that resistor responsible to the output voltage and just adjust it?

https://datasheets.maximintegrated.com/en/ds/ICL8069.pdf

Fungus:

--- Quote from: Trader on July 12, 2021, 07:50:39 pm ---Sorry about my naive question, I know the way to calibrate those DMMs is through the EEPROM, but since they use the ICL8069 voltage reference, why not discover that resistor responsible to the output voltage and just adjust it?

--- End quote ---

Simple: Because each range has a separate calibration. If you change that then you make everything change.

Plus: I don't think there's a potentiometer. The reference is set approximately then everything else is done in software.

Trader:

--- Quote from: Fungus on July 12, 2021, 07:53:29 pm ---Simple: Because each range has a separate calibration. If you change that then you make everything change.

--- End quote ---


--- Quote from: floobydust on October 24, 2020, 08:09:45 pm ---If you did calibrate it perfectly, that is not long-term accuracy because it uses vanilla 1% tolerance resistors and an ICL8069, both of which will drift with temperature and age.

--- End quote ---

I thought the DMM lost the calibration because of the ICL8069 and the adjust-resistor. So, fixing them will restore the initial characteristics when EEPROM was set up.

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