Optical Replacement of pH Electrode

The development of a noninvasive, self-contained optical pH sensor probe intended as a direct replacement for a pH electrode is presented. It uses a fluorescent excitation-ratiometric pH sensing dye in a patch. The patch is excited by light emitting diodes of differing wavelengths which are controlled by a microcontroller (MCU). The emission levels are measured by analog circuitry and their ratio is converted by the MCU into a linear output which mirrors that of a conventional pH electrode. The optical sensor readings were consistent with readings from a glass pH electrode with average difference .061 pH. This sensor allows noninvasive, low-cost optical pH sensing with the ability to interface with existing pH monitoring equipment.