Convert value

[Artic1980]

Good evening I'm trying to read the pH of the pool but I can not convert the value into ph.
I that 2.5v correspond to 7ph and 3.05 to 4ph how can i convert it?
The sensor is connected to an asd1115 and an esp8266
thank you

[Domosapiens]

Assuming the sensor is linear, you have something like this,
where x is Volt and looking for y as Ph


So the formula is:
y=a+bx
You posted 2 answers for the formula:
7=a+2.5b (1)
4=a+3.05b (2)

Rework (1)
a=7-2.5b
Substitute in (2)
4=7-2.5b+3.05b
Calculate b=-5.4545
Substitute in (1)
Calculate a=20.6363
Your formula:
y=20.6363-5.4545b

In practice:
To get Ph: read the Voltage, multiply by 5.4545 and subtract it from 20.6363

But first do some input checking:
0V gives a Ph of 20 (rubbish!)
More than 3.78V gives a Ph lower than 0 (rubbish!)

Note 1:
the - sign for b gives a negative slope: the more volt, the lower the Ph
so .. the slope in the picture is just an example of a positive slope

Note 2:
Calculations with 1 decimal will be sufficient

[Artic1980]

Thanks a lot tomorrow text


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[Artic1980]

Now is perfect. Thank


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