Development of a medical fiber-optic pH sensor based on optical absorption

• Published in: IEEE transactions on biomedical engineering 1992-05, Vol.39 (5), p.531-537
• Main Authors: Wolthuis, R., McCrae, D., Saaski, E., Hartl, J., Mitchell, G.
• Format: Article
• Language: English
• Subjects: Absorption; Azo Compounds; Biological and medical sciences; Biomedical optical imaging; Blood; Blood Gas Analysis - instrumentation; Calibration; Electromagnetic wave absorption; Equipment Design; Evaluation Studies as Topic; Fiber Optic Technology - instrumentation; Humans; Hydrogen-Ion Concentration; Indicators and Reagents; Investigative techniques, diagnostic techniques (general aspects); Laboratories; Light emitting diodes; Medical sciences; Mirrors; Miscellaneous. Technology; Optical fiber sensors; Optical Fibers; Optical pulses; Optical sensors; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Sensor systems; Sterilization; Triazines
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/10.135548

A new fiber-optic pH sensor system has been developed. The sensor uses an absorptive indicator compound with a long wavelength absorption peak near 625 nm; change in absorption over the pH range 6.8 to 7.8 is reasonably linear. The sensor is interrogated by a pulsed, red LED. The return light signal is split into short- and long-wavelength components with a dichroic mirror; the respective signals are detected by photodiodes, and their photocurrents are used to form a radiometric output signal. In laboratory tests, the sensor system provided resolution of 0.01 pH, accuracy of +or-0.01 pH, and response time of 30-40 s. Following gamma sterilization, laboratory sensor testing with heparinized human blood yielded excellent agreement with a clinical blood gas analyzer. Excellent sensor performance and low cost, solid-state instrumentation are hallmarks of this sensor-system design.< >