As I look back over my experience with pH and conductivity measurements, the following opportunities stand out.
(1) Selecting the best sensor technology for a wide range of process conditions
(2) Eliminating measurement noise
(3) Predicting sensor demise
(4) Developing process temperature compensation
(5) Developing inferential measurements of process concentrations
(6) Finding the optimum sensor location
You really can’t ship most chemicals to the electrode manufacturer and electrodes sent back after a problem often don’t tell the whole story including handling, maintenance, and process conditions. The manufacturer’s application support people are often at a loss as to what was really the problem. Then there are the insidious spikes that come and go with no sense of the source or the fix.
The biggest source of continual pH noise is fluctuations in acid and base concentration at the electrode. Operating points on the relatively steep portion of the titration curve require a degree of mixing that goes way beyond the norm. Electrodes are moved to a location that is the best compromise between noise and measurement delay and lag.
Users can install a test setup in the plant to compare the performance of various electrode technologies but this is time consuming and does not allow experimentation. Tests in the lab usually involve “dumb” lab meters with the data ending up in a spreadsheet oblivious to the historian and the tools in the DCS for neural networks and data analytics.
To see if the opportunities are more than a dream and if the problems can become just a bad memory, check out the InTech web exclusive article “Opportunities for Smart Wireless pH, Conductivity Measurements“