This is a KR Project site for a DIY arduino based photometer for pH measurement based on the original OpenSource work of Bo Yang et.al.  The initial goal of this project was to replicate the photometer, methods, and describe results here.

The project goes back to conversations with folks in the academic community interested in affordable DIY instruments to measure and log pH data.  They were especially interested in an optical method published by Yang et.al because of its potential to simplify pH sampling of sea water.  We tried glass bulb designs – which work but are messy, fussy, and fragile. An optical method sounded attractive.

The authors of the original DIY photometer obtained .01 unit pH accuracy.

Let’s build one and see if it works!

I did.  It does work, but the accuracy is barely 0.5 pH units.   After experimenting and troubleshooting the original build,  not surprisingly, accuracy depends greatly on the quality and precision of the physical build.  Physical tolerances are in the thousandths of an inch.  A second area is that the original design is based on a 100 ml sample, which is huge in comparison to the standard 3ml sample used by the lab photospectrometer, and at a dilution of 50 ul to 3 ml

This site will change as we get further into the project.  Initially the focus is on the building the hardware and tweaking software – relatively simple stuff.   After that comes calibration and testing with meta-cresol purple, a dye found to be appropriate for measuring the pH of seawater.  Everything you need to know about the design is described in the original paper below… here we’re just talking about building and implementation.

DIY Photometer published by Bo Yang, Mark C. Patsavas, Robert H. Byrne ⁎, Jian Ma  — 

Seawater pH measurements in the field: A DIY photometerwith 0.01 unit
pH accuracy