Abstract: A method and instrument capable of producing an audible tick that increases with detected gas concentrations, is suitable for indicating relatively low levels of gas concentrations, and enables the adjustment of the tick rate to provide an accurate audible indication of gas levels at higher concentrations. The method and instrument entail sensing the presence of the gas and generating an analog sensor output based on a concentration of the gas in the environment, and then processing the analog sensor output through an audio circuitry to generate therefrom an audible tick having a frequency in proportion to the analog sensor output. The processing step includes the use of an analog control loop signal to selectively increase and decrease the frequency of the audible tick.

Abstract: A method and instrument capable of producing an audible tick that increases with detected gas concentrations, is suitable for indicating relatively low levels of gas concentrations, and enables the adjustment of the tick rate to provide an accurate audible indication of gas levels at higher concentrations. The method and instrument entail sensing the presence of the gas and generating an analog sensor output based on a concentration of the gas in the environment, and then processing the analog sensor output through an audio circuitry to generate therefrom an audible tick having a frequency in proportion to the analog sensor output. The processing step includes the use of an analog control loop signal to selectively increase and decrease the frequency of the audible tick.

Abstract: A method and instrument capable of accurately detecting the presence of a gas and accurately measuring the concentration of the gas in, for example, the environment. The method and instrument sense the presence of a gas with a sensing element whose output is linear to the concentration of the gas in the environment, and process the output of the sensing element through a nonlinear amplifier having a higher gain at lower levels of the output than at higher levels of the output so that the nonlinear amplifier amplifies the output of the sensing element at the lower levels thereof and avoids signal saturation at the higher levels thereof. The method and instrument then deliver the amplified output of the nonlinear amplifier to an audio circuit that produces an audio output having a property in proportion to the amplified output of the nonlinear amplifier.

Abstract: A method and instrument capable of accurately detecting the presence of a gas and accurately measuring the concentration of the gas in, for example, the environment. The method and instrument sense the presence of a gas with a sensing element whose output is linear to the concentration of the gas in the environment, and process the output of the sensing element through a nonlinear amplifier having a higher gain at lower levels of the output than at higher levels of the output so that the nonlinear amplifier amplifies the output of the sensing element at the lower levels thereof and avoids signal saturation at the higher levels thereof. The method and instrument then deliver the amplified output of the nonlinear amplifier to an audio circuit that produces an audio output having a property in proportion to the amplified output of the nonlinear amplifier.

Abstract: A thermal gas sensing apparatus for a gas detector is provided with a gas compartment containing a gas, a gas sensor exposed to the gas in the gas compartment, and a temperature sensor exposed to the gas in the gas compartment. The gas sensing apparatus includes a circuit for generating a gas signal having a magnitude which relates to the heat capacity of the gas and a circuit for generating a temperature signal having a magnitude which relates to the temperature of the gas. The apparatus includes a circuit for supplying a variable magnitude of electrical current through the gas sensor to cause the resistance of the gas sensor to remain substantially constant. The apparatus also includes a difference amplifier for generating a gas concentration signal based upon the temperature signal and the gas signal.

Abstract: A refrigerant gas leak detector for detecting the location of leaks of refrigerant gas such as halogen has a sensing tip with a pair of electrodes across which a relatively high voltage is generated to cause a corona current to pass through the electrodes. The voltage applied across the electrodes is varied to maintain the corona current through the electrodes at a substantially constant magnitude. The leak detector includes a gas sensing circuit that detects changes in the concentration of refrigerant gas by sensing the voltage applied to the electrodes. The sensitivity of the gas sensing circuit is automatically varied based on the concentration of refrigerant gas present. The leak detector includes a signal generating circuit that causes a number of audible and visual indications to be generated based on the concentration of refrigerant gas sensed as well as other operating conditions.

Abstract: A gas leak detector that operates on the corona principle having a sensing tip with a pair of electrodes across which a high voltage is provided to generate a corona current through the electrodes. The sensing tip includes a first electrode having a conductive housing with a first end having a gas inlet formed therein and a second end and a flow passage formed therein. The flow passage has a first bore provided between the gas inlet and the second end of said conductive housing and a second bore having a diameter smaller than that of the first bore. The second bore is provided between the first bore and the gas inlet of the conductive housing and abuts the first bore to form an edge in the interior of the housing. The flow passage also has a third bore of a diameter smaller than that of the second bore provided between the second bore and the gas inlet. The gas leak detector also includes a second electrode provided in the interior of the conductive housing.

Abstract: A battery-powered gas detector comprises a gas sensor coupled to a current source and a power supply. The power supply generates a relatively high voltage when the gas sensor is warming up and a relatively low voltage after the sensor has warmed up. The gas sensor, which is responsive to the presence of a gas, is coupled to an amplifier having a variable sensitivity circuit. The amplifier is connected to a microprocessor that determines the concentration of the sensed gas and provides a visual indication of the concentration on a display. The gas detector can sense the presence of a variety of different gases. The gas concentration of the sensed gas is determined based upon the magnitudes of a gas sensing signal generated by the amplifier, a calibration signal generated during a calibration routine when the detector is in a controlled environment, and an error signal generated when the detector is in a no-gas environment.