Scott Technologies, Inc.

L Rodney Bristol

A gas measuring device for measuring a presence of a target gas in a fluid medium includes a sensor having a sensing element and a heating element being configured to heat the sensing element to a predetermined operating temperature. The sensing element is responsive to the target gas such that at least one electrical property of the sensing element varies based on a presence of the target gas, and the electrical property of the sensing element is measured by the gas measuring device. The gas measuring device also includes a control circuit having a heating element controller connected to, and measuring an electrical property of, the heating element. The control circuit also includes a heater power supply supplying power to the heating element, wherein the heating element controller is connected to, and controls the operation of, the heater power supply based on the measurement of the electrical property of the heating element.

Gas measuring device and method of operating the same

A gas detector is provided. The gas detector includes a measurement source of optical radiation, a reference source of optical radiation, a measurement detector configured to provide an output signal indicative of a gas of interest, a reference detector configured to provide an output signal at least partially independent of the gas of interest, a measurement optical path extending from the measurement source to the reference and measurement detectors, and a sample region for receiving a gaseous sample. The sample region is located along the measurement optical path. A window is positioned in the measurement optical path downstream from the measurement source and upstream from the reference and measurement detectors. The window is partially transparent to optical radiation and partially reflective to optical radiation. The window is positioned to either reflect a portion of the optical radiation emitted by the reference source into the measurement optical path or to allow a portion of the optical radiation emitted by the reference source to pass through the window into the measurement optical path.

Optical gas detector

A system and method for measuring fluid flow rate in a system where fluid is pumped, such as a gas monitoring instrument where gas is pumped from a space such as a room or enclosure through a conduit to a sensor. The flow of gas through a pump is determined by measuring motor back-e.m.f. which is proportional to motor speed. In a system where motor speed is regulated by pulse width modulation of the motor drive voltage, the back-e.m.f. is sampled during intervals between the drive pulses applied to the motor, and in a further aspect the sampling is done at selected, spaced-apart or infrequent intervals such as once for every ten or once for every hundred motor drive pulses. Advantageously, in an instrument that uses a microprocessor and analog-to-digital converter to measure gas-concentration, the same microprocessor and converter can provide the PWM control of the pump, in response to the back-e.m.f. generated by the pump motor between the drive pulses. The microprocessor compares the output of the analog-to-digital converter, corresponding to the back-e.m.f., which in turn corresponds to the pump motor speed, to a set-point value, representative of the desired pump motor speed. The processor then adjusts the PWM to control the pump motor to achieve and maintain the desired speed. As a result, in a gas monitor, the gas-flow rate may be maintained close to a desired gas flow rate regardless of the voltage supplied by the battery or other voltage source, regardless of the degree to which the gas is filtered, and under a wide range of operating conditions.

Speed and fluid flow controller

A gas detection sensor system including active and reference elements (R , R ) are arranged in a modified bridge circuit ( ) which allows power (V ) to be supplied seperately to the active and reference element (R , R ). A digal processor ( ) monitors the resistances of the elements (R , R ) to control a pulse-width modulator supplying power to the elements, thereby maintaining nearly constant temperatures in the sensor elements (R , R ) and to translate the decrease in power needed to maintain constant temperature on the catalytic element into an output proportional to the concentration of combutible gas in air. The system periodically measures the resistance of the elements (Rref, Rsense) and enables dual operating modes of catalytic-bead detector. One active or reference element (R , R ) can alternately measure low concentrations of combustible gases up to the lower explosive limit (LEL) or measure high concentrations, up to 100% by volume.

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Chalfont, PA, United States of America

L Rodney Bristol