Aneng Q1 Multimeter Adjust\Calibrate

[alaaj99]

Hello 👋
Is there a way to Adjust\Calibrate Aneng Q1 Multimeter.
Short story, I got the Multimeter and noticed it's a "Battery hungry" so I replaced the normal AA batteries with 3.7 lithium-ion.
During the process I "accidently" ripped off the traces of positive and negative of the AA battery holder.
After resoldering the traces, the Multimeter started showing Inaccurate measurements, here are a few examples:
Measuring AC 238V, It's actually 230V
Measuring DC 4V, It's actually 3.9V
Measuring Ohm 5.86K, It's actually 5.65k.
Measuring Temp starts at 45C/113F. and so on.
The Multimeter doesn't have a potentiometer inside it.
There's a component inside labeled ICL8069, I think it's called TVS, it should be 1.2V voltage reference, but it's measuring 1.236V

Yes, I replaced the leads. No, the Multimeter doesn't get any voltage above 3.6V from the lithium-ion battery.
Any help is appreciated.

Full review for Q1 Multimeter from eevblog YT channel:

[Phil1977]

Calibration is stored in the EEPROM by the manufacturer. Many dirt-cheap DMMs have no way to access the calibration.

Are you sure it´s out of calibration? Can you compare to any other DMM? The numbers you´ve told, especially about mains voltage, may absolutely be in their tolerance range.

[Fungus]

If you're 100% sure it got worse then check for flux contamination, etc., on the PCB.

Give it all a good clean with isopropyl alcohol...

[Atlan]

Does the stabilizer have blocking capacitors?  It doesn't oscillate.

[alaaj99]

Calibration is stored in the EEPROM by the manufacturer. Many dirt-cheap DMMs have no way to access the calibration.

Are you saying That the Calibration is done by the EEPROM?
Because I DID reprogram it using a file found online for the same DMM but "Under a different brand".

Are you sure it´s out of calibration? Can you compare to any other DMM? The numbers you´ve told, especially about mains voltage, may absolutely be in their tolerance range.

Yes, I did compare it with a couple of other DMMs. Only mine shows a big difference.

[alaaj99]

If you're 100% sure it got worse then check for flux contamination, etc., on the PCB.

Give it all a good clean with isopropyl alcohol...

Gonna give it a try 

[Gyro]

You appear to have glued the lithium cell over the top of the high impedance trace (after a couple of series resistors) from the V/Ohms socket, that could drop your reading - particularly as you seem to have a much greater reduction in reading at 238V than you have at 4V.

Looking at the positioning of the cell, you have unfortunately totally compromised safety too - it's on top of a direct track from the V/ohms socket (before the PTC) and [two] Com socket referenced current range tracks. I wouldn't let it anywhere near mains (where the 238V presumably came from?). You're one tiny step away from a loud destructive bang I'm afraid.


Edit: You also have the the hazardous issue of potentially having test leads inserted at the same time as you are charging the battery. This could cause dangerous voltage on the charging socket. The COM lead is also not at the same potential as the battery -ve, something that has blown up several peoples' meters when they tried to measure the voltage of the meter's own battery.

[Fungus]

Are you saying That the Calibration is done by the EEPROM?

Yes.

[alaaj99]

You appear to have glued the lithium cell over the top of the high impedance trace (after a couple of series resistors) from the V/Ohms socket, that could drop your reading - particularly as you seem to have a much greater reduction in reading at 238V than you have at 4V.

Looking at the positioning of the cell, you have unfortunately totally compromised safety too - it's on top of a direct track from the V/ohms socket (before the PTC) and [two] Com socket referenced current range tracks. I wouldn't let it anywhere near mains (where the 238V presumably came from?). You're one tiny step away from a loud destructive bang I'm afraid.


Edit: You also have the the hazardous issue of potentially having test leads inserted at the same time as you are charging the battery. This could cause dangerous voltage on the charging socket. The COM lead is also not at the same potential as the battery -ve, something that has blown up several peoples' meters when they tried to measure the voltage of the meter's own battery.

Thank you very much for enlighten me 

[Gyro]

Is it still possible to restore the meter to original state? You mentioned the solder pads but I don't know how well the cell is fixed down (I can see that it has a metal foil outer though). The Nokia cell's 700mAh remaining capacity is very poor when you compare it to easily available and cheap to buy 2500mAh NiMH low self-discharge rechargeable AA cells (Lidl for instance).

You might find that without the cell there, the calibration returns to normal. 1.236V is normal for an ICL8069 - the Renesas datasheet shows 1.2V min, 1.23V typ. and 1.25V max, so it is well within spec. it's not a close initial tolerance part.

Restoring a reasonable level of safety would certainly be desirable and I would hate to see you trash the meter with a failed EEPROM adjustment attempt.

[alaaj99]

Are you saying That the Calibration is done by the EEPROM?

Yes.

Thank you very much, It was actually the EEPROM.
Luckily I did a backup of the EEPROM of my meter before flashing the one I found online.
Now after I restore it, everything is working great 

[alaaj99]

Is it still possible to restore the meter to original state? You mentioned the solder pads but I don't know how well the cell is fixed down (I can see that it has a metal foil outer though). The Nokia cell's 700mAh remaining capacity is very poor when you compare it to easily available and cheap to buy 2500mAh NiMH low self-discharge rechargeable AA cells (Lidl for instance).

You might find that without the cell there, the calibration returns to normal. 1.236V is normal for an ICL8069 - the Renesas datasheet shows 1.2V min, 1.23V typ. and 1.25V max, so it is well within spec. it's not a close initial tolerance part.

Restoring a reasonable level of safety would certainly be desirable and I would hate to see you trash the meter with a failed EEPROM adjustment attempt.

Thank you.
All the points you referred to, specially about safety, will be considered.
The meter is working fine now, after restoring the original EEPROM file. It was the problem.
I'm replacing the Lithium battery with Ni-Mh batteries as you suggested.

[Gyro]

...
The meter is working fine now, after restoring the original EEPROM file. It was the problem.
...

Good save.

[alaaj99]

The problem is now SOLVED. Thanks everyone.
The wrong, not so accurate readings, was because I flashed the EEPROM of my meter with a random .bin file found online for the same meter BUT UNDER A DIFFERENT BRAND.
I searched online and found that this meter is sold from different brands and models:
Aneng Q1
Mustool Q1
Zoyi ZT x
Richmeters 409B ...... and maybe there's more
I compared two EEPROM files found online from different brands with the one I have and found they're not the same.
Anyway for anyone having the same problem, my meter is (Mustool Q1 9999) and here's a link for the EEPROM .bin file:

https://mega.nz/file/qt4gVBCB#8KeiUPCWBYPU04yP0JJTDTrvfw8L_JxT5Js1C2mdtgw