Semiconductor gas sensor having linearized indications
First Claim
1. A combination which includes semiconductor elements for measuring atmospheric concentrations of reducing gases comprising a gas sensor whose conductivity varies in accordance with variations in the concentration of ambient reducing gases, resistance means in series with said gas sensor for establishing a reference voltage, circuit means interconnecting said resistance means with the non-inverting inputs of a plurality of voltage comparators, an adjustable resistance means of a magnitude substantially equal to the response of said sensor at its maximum value, a thermistor in parallel with a fixed resistance and in series with said adjustable resistance means and with a voltage divider comprising a plurality of fixed resistors respectively connected with the inverting inputs of said plurality of voltage comparators, and a light emitting diode in series with the output of each of said comparators for selectively indicating a particular degree of ambient reducing gas concentrations.
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Abstract
Atmospheric concentrations of reducing gases are measured and indicated by a gas sensor whose conductivity varies in accordance with variations in the concentration of ambient reducing gases, a resistance in series with the gas sensor for establishing a reference voltage, a circuit interconnecting the resistance with a linearizing circuit including the non-inverting inputs of a plurality of voltage comparators and with the inverting input of a fault detecting comparator, an adjustable resistance of a magnitude substantially equal to the response of the sensor at its maximum value, a thermistor in parallel with a fixed resistance and in series with the adjustable resistance and with a voltage divider including a plurality of fixed resistors respectively connected with the inverting inputs of the plurality of voltage comparators together with a light emitting diode in series with the output of each voltage comparator, each light emitting diode indicating a concentration of an ambient reducing gas in terms of parts per million, and the non-inverting input of the fault detecting comparator is connected with a reference voltage to indicate an open circuit condition.
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Citations
14 Claims
- 1. A combination which includes semiconductor elements for measuring atmospheric concentrations of reducing gases comprising a gas sensor whose conductivity varies in accordance with variations in the concentration of ambient reducing gases, resistance means in series with said gas sensor for establishing a reference voltage, circuit means interconnecting said resistance means with the non-inverting inputs of a plurality of voltage comparators, an adjustable resistance means of a magnitude substantially equal to the response of said sensor at its maximum value, a thermistor in parallel with a fixed resistance and in series with said adjustable resistance means and with a voltage divider comprising a plurality of fixed resistors respectively connected with the inverting inputs of said plurality of voltage comparators, and a light emitting diode in series with the output of each of said comparators for selectively indicating a particular degree of ambient reducing gas concentrations.
Specification