An investigation of a condenser microphone as a pressure transducer
Schwartz, Robert, 1950-
Pfeiffer, Paul E.
Master of Science
The device described is a preasure-sensitive transducer. commercially available condenser microphone, a Stephens model C-1 was used as a capacitor manometer. The instrument was developed for use in breath velocity studies where pressures encountered are thousandths of pounds per square inch. A study of the literature indicated that a number of methods have been used to obtain information breath velocity studies of which the capacitor manometer is one of the most promising. Its use makes possible high sensitivity and short rise-time which is important in providing useful information in respiratory studies. The method employed is based on the um of the microphone as a variable load impedance in a cathode follower driven by a crystal controlled oscillators The voltage impressed across the microphone in the range of 8 is then detected and emplified. A dummy channel, an electrical equivalent of the microphone and its cable, is used in a balancing arrangement to develop a variable d-e centering voltage for the pen recorder used with this instrument and to provide the means for an output balanced to ground. A voltage-regulator power-supply is used to assist in attaining high useful sensitivity by reducing drift and ripple attibutable the power supply. A number of pen recorded trace of breathing are included. The circuitry, its development, testing, and operation is discussed addition to suggestions for additional work and further study. ,