Hi Everybody,

I'm building my Pool controller using PH and ORP sensors to check water quality, I'm using ESP8266 with ESPHOME connected to Home assistant to monitor these sensors.

For PH sensor there is no problem but with ORP sensor I'm quite confused due to it doesn't get normal values.

In my case I've connected a multimeter to read Voltage values from df robot orp board, and it fits with analog value I have in ESP8266 so the reading is correct.

I have a very estrange readings in comparison with manual testers ( I use strip test and also liquid test ), In my case, I can see with manual tests that Free chlorine is low but ORP sensor read values of 874 mV.

I have an orp calibration solution that marks 256mV, when I put the probe inside this liquid solution the values were more or less 256 mV but when I put again the sensor with the swimming pool water it cames back to more than 800 mV, I though it was due to a PH deviation but it reads in 7,3 so it is correct.

I attach here the readings during calibration and after several hours reading after.

Could you indicate me what is happening? Is there a problem with the probe?

Thanks.