pH probe fluctuation issues

[disaster999]

@Sral Hope you can help.

Long story short, after jumping through countless hoops, I bit the bullet and bought the EZO carrier isolator board hoping this will fix my issue. I also used a linear power supply which claims to have stable ultra low noise supply. On the bench with that setup im getting 0.02+/- fluctuations but once I place the setup into my tank the fluctuations jumps to 0.2+/-.

Heres my setup right now, Ive completely eliminated the prefboard

Current reading right now

Talking to EZO, They had my give them my calibration data, With the help of AI, they gave me a python script to calibrate and export the calibration

Export Info (Strings, Bytes): ?EXPORT,6,60
Received string: 884CC4457D19
Received string: 0FC3E0F73DC3
Received string: 010101EB5180
Received string: 401E85DB4048
Received string: E11241001336
Export completed.

Saved Calibration Data:
884CC4457D19,0FC3E0F73DC3,010101EB5180,401E85DB4048,E11241001336

 

[Sral]

Hm. Have you ever calibrated the sensor using the I2C interface ?
It would be useful if you didn't, I reckon. Since then one could be reasonably sure that the noise is real voltage noise and not an artifact from bad calibration.
Can you confirm that your probe shows the correct values in at least 2 calibration solutions ?

Judging by the EZO_pH datasheet it isn't immediately obvious what the calibration data represents, but one could probably guesstimate with a bit of time. I might give it a try when it seems necessary.


For now I'd focus on the fact that noise when not in the tank is reasonable at 0.02 but jumps to 0.2 when it is in the tank. Can you tell me what your power supply is ? Best might be a link to where you got it from.

I'd first try different power supplies, including isolated ones. Like beefy phone chargers or a power bank, if you have one at hand with enough output power. The power bank (if it can power it sufficiently without too much noise) would have the benefit of being guaranteed to be isolated.