I bought an ORP Buffer solution (468mV).
The reading is correct, but I observe a drift in the reading.
It slowly increase... I did not wait for a stable value but it increased from 458 to 490 in around 5 minutes.
I don't know what could generate that drift.
Maybe it could be a capacitive effect ?

Yes, that is the correct use of the formula. Have you tried measuring the ORP of a calibration fluid with a known ORP to see how far off the probe is? Also, if there are electrical components like pumps running in the pool it could be causing interference. Hi, thank you for fast answer. Buying cali...

Hi, I made a pool ORP regulator based on arduino + phidget 1130 + ORP probe. My ORP readings are high arount 800mV. I am applying the owner's manual formula : First get ADC Value (Arduino is 10bits = 1024 values), Reference Voltage is 5V : ADC_Value = analogRead(A0) * 5 / 1023.0; PhidgetORP = ((2.5 ...