Microprocessor based pH monitoring and transmitting system

The authors show how a microprocessor can be used to provide the accuracy and flexibility that is required for a general-purpose industrial pH measurement system. Important features considered are automatic, precise temperature compensation with a low-cost temperature sensor, automatic compensation for system offsets and drift, and diagnostics from the front panel. A systematic design procedure that includes specifications, a theoretical analysis of error sources, careful consideration of important design criteria, and the system hardware and software design is described. A special technique of multiplexing a digital-to-analog converter for analog-to-digital conversion and output monitoring is used to keep overall cost low. A nonvolatile memory is used to store the calibration constants. A prototype has been built, and the results obtained under simulated and actual conditions are discussed