Phidget pH / ORP adapter

Interfacing the Phidgets pH / ORP adapter with the Arduino is fairly simple.   I wanted to post the formulas and Wiki link here.

http://www.phidgets.com/docs/1130_User_Guide

Make sure you switch the adapter to the correct mode, pH or ORP.

pH formula for the Arduino sketch:    PHLevel = (0.0178 * (PHprobe) - 1.889);   This assumes 25 degree C.


ORP formula for the Arduino sketch:   mV = ((2.5 - ORPprobe / 200) / 1.037)* 1000;

Words of Caution from Phidgets

The pH Adapter Board should be used to measure solutions that are 'electrically quiet'. Measuring pH in electrically noisy environments such as tanks with mixing pumps, and even other measuring devices is not recommended.

I have had some noise interference from the hot tub jets when the filter cycle is running, but overall the Phidgets adapter has worked well in the hot tub environment.