### Problem with tds meter#44308

By weedcuper
#44308
Sup guys. Just have looked at tds-meter Arduino code and can't understand one thing:
Code: Select all
``````tdsValue=(133.42*compensationVolatge*compensationVolatge*compensationVolatge - 255.86*compensationVolatge*compensationVolatge + 857.39*compensationVolatge)*0.5;
``````
Where does this formula come from? And how did you calculate this coefficients?

### Re: Problem with tds meter#44312

#44312
I am building a ESP8266 project with a water flow and TDS meter to measure the status of my water filter. The water flow meter has been easy to get working so far, but I have not yet figured out how to interface the TDS meter. Ideally it would be in-line and use a quick connect fitting. This is what I am thinking of getting. How could I get the data that this puts out, into my Arduino?blossomfurnishings.com/acrylic-rectangle-dining-table/
Last edited by borhadepriti516 on Fri Mar 12, 2021 1:07 pm, edited 1 time in total.

### Re: Problem with tds meter#44313

By 347945801
#44313
This formula is fitted out by our technicians through experiments, all relying on experimental data and no reference materials.

### Re: Problem with tds meter#44314

By 347945801
#44314
This sensor only needs to read a simple analog voltage. You connect the 3 wires connected to the Arduino in the picture to the ESP8266, and connect the power, ground, and GPIO pins respectively.

### Re: Problem with tds meter#44714

By jonathantelling69
#44714
I too would like to know how this equation works. I'll add more details later. I understand how the temperature compensation is calculated. Just that the output from this board is in voltage, which is converted by the ADC.... Unsure how the above equation converts that back to EC for calculation. The reason I want this, is that the provided lib for calibration only works for normal aruino, not ESPs.. (Yes I changed the pin to A0 in the cpp file, ).