Review on Wendry Quality Testing Domestic Hydroponics by John Bennett

I am using this with esp8266. It should be noted that you need to calibrate this and do a 2 point calibration, one at 1000ppm, another at 500 or whatever range you expect to measure. Don't calibrate 0ppm at 0 volts with a microcontroller based ADC unless you plan to use a terminal cap and build an isolation circuit for it. 12-bit ADCs are often noisy even with a stable reference voltage. If you calibrate 0 ppm at 0 volts, the entire scale will be linearly distorted. Use a lower non-zero range instead, e.g. B. 50ppm. This keeps your reading noise free. and you can probably still read zero. It took me a day to get to this and it works great. I calibrated at 300, 840 and 1000. At 840 I usually go into my nutrient reservoir.