As a Water Quality professional working in the drinking water field, I know how important it is to accurately monitor the disinfectant levels in the drinking water that gets served to the public. Usually, that means taking weekly grab samples in the distribution system and measuring free chlorine or total chlorine residual via a DPD colorimetric test. Sometimes, however, it would be nice to know what’s going on with the disinfectant residual when you’re not out there to take a sample. It would be nice to log the residual over time. That’s why I wanted to put together an inexpensive data logger that would measure and log pH, oxidation-reduction potential (ORP), and temperature. From those three parameters, the disinfectant residual can be approximated, not to mention that they are interesting parameters to measure and log in their own right. In my research for this project, I also came across some other uses in which this device might come in handy. It seems that aquarists regularly measure these parameters to keep their aquariums healthy, and it can also be used to keep track of oxidant levels in apool or spa. These are three very commonly measured parameters in water system security devices that are being used more and more to make sure that a water system is not being tampered with. And, it can be used in the lab for testing oxidant dosing, or measuring reaction kinetics.
My criteria for the project were that it had to be fairly easy to make; relatively inexpensive; and pretty accurate. I think what I’ve created meets those criteria, and I hope you do, too!
Step 1: Parts and Supplies