Apparatus for controlling environmental conditions, especially suitable for use underwater

Abstract

Abstract The disclosure illustrates a self-contained closed circuit type underwater breathing apparatus for diver use. A plurality of three or more oxygen sensor cells, each thermistor temperature compensated, are exposed to the gas stream in the system, each providing a current resulting in voltage drop across the thermistor, directly related to oxygen concentration, which voltages then are electronically processed to operate oxygen supply means, whereby oxygen partial pressure is maintained within a predetermined range. In the processing, amplified signal voltages are electronically mathematically averaged and processed to deliver a single control signal to an oxygen solenoid valve. The system is adjusted at atmospheric pressure to provide one half atmosphere oxygen partial pressure at a selected voltage level, e.g., about 2.4 volts average amplified cell voltage. As the quantity of oxygen thereafter varies in use by the diver, the average voltage varies linearly and the solenoid acts responsively thereto. Each amplified cell output is also connected into separate alarm and visual indicator circuitry so that should any cell provide a voltage corresponding to oxygen partial pressure below or above a predetermined safe oxygen range, an audible alarm is sounded and the diver may observe the individual indicators provided for each of the sensor cells and, thereupon, determine emergency remedial steps. Normally, the diver will presume any two similar partial pressure indicators to be correct. The design of the system is such that the electronic circuitry responds to limit, or stabilize, the effect of a spurious voltage input upon the average voltage via transistor clipping circuitry and an associated regulated voltage source. Thereupon a non-varying voltage, which is not outside the selected saft range constantly appears in the average voltage. Accordingly, the new effective average voltage continues effectively to maintain a suitable oxygen partial pressure as long as the signals from the remaining cells themselves are a correct measure of the oxygen partial pressure actually in the system.

Inventors

• 👤 J Kanwisher
• 👤 W Starck

Bibliographic Details