Abstract: A hush mode disabling device for a smoke alarm having a self-test function, a hush mode that engages upon activation of the self-test function to silence or desensitize the smoke alarm for a predetermined period of time, and a remote self-test controller. An improvement includes a hush mode disabler for determining whether the self-test function has presently been activated by the remote self-test controller and for disabling the hush mode if the self-test function has presently been activated by the remote self-test controller.

Abstract: A permeable protective coating for a single-ship hydrogen sensor. A hydrogen-permeable coating is applied to a semiconductor wafer containing hydrogen sensor dies, prior to dicing of the wafer. The permeable coating is preferably an organic spin-on polymer, and the hydrogen sensors preferably include hydrogen-sensing elements composed of a palladium nickel alloy.

Abstract: A production system comprises a plurality of fabrication apparatuses arranged in series for performing a sequential processing of work units applied to the system. All or some of the fabrication apparatuses are respectively equipped with sets of lamps each of which visually indicates fabrication states of the corresponding fabrication apparatus by energizing or de-energizing different colored lamps. A lamp control signal monitor is provided in each fabrication apparatus having the set of lamps. The lamp control signal monitor receives lamp control information used to energize or de-energize the colored lamps, and stores therein data indicative of start and finish time points and time durations of energization and de-energization of the colored lamps.

Abstract: A low power local alarm indicating system for interconnectable detectors enables a viewer to, after the fact, determine which detector or detectors had previously gone into a local alarm. An alarm latch, such as a bistable multi-vibrator circuit, is set each time the respective detector goes into a local alarm. Subsequently, if the detector's test switch is activated, a local alarm visual indicator is provided. In a disclosed embodiment, the indication is provided by blinking a light emitting diode on the detector, for a predetermined interval. Where multiple detectors are interconnected, each detector that goes into alarm not only sets its local alarm latch and emits a local alarm, it also generates an interconnect alarm signal to the remaining interconnected detectors. The interconnected detectors go into alarm at least for as long as the interconnect signal is present.

Abstract: A gas detector-alarm comprises a hot-wire gas sensor 1 having an actuating power control 7 that supplies pulsed actuating power with a cycle T0 when the concentration of gas detected by the hot-wire gas sensor is lower than a first reference level, with a cycle T1 that is shorter than said cycle T0 at least once when the concentration of gas exceeds a second reference level, and with a cycle T0 again after an alarm has been triggered.

Abstract: The current invention discloses a wireless monitoring system. The system has one or more monitoring devices. Each device can transmit data and receive messages from an output center or alarm system. The output center can also transmit and receive messages. Both the output center and each device preferably have a transceiver that enables both the transmission and receipt of messages. No remote terminal units or hardwiring is required for the system to function. The system is truly a wireless gas monitoring system. The system may use low earth orbit satellite technology, or licensed radio frequencies or any other means to wirelessly transmit and receive messages.

Abstract: A smoke detection system comprises a manifold (4) connected to a series of sampling pipes (2). A fan (6) which draws a large volume of sampling air through the sampling pipes is connected to the inlet manifold and a small proportion of that air is directed to the inlet of a smoke detector (12), the outlet of which is connected to the manifold. The configuration obtained by the connection of the outlet from the detector into the inlet manifold provides a large pressure drop across the flow path through the detector. As a result of the large pressure drop, a filter (10) for removing dust and other contaminants can be incorporated in the flow path and the filter can also incorporate a fine filtering stage to produce a secondary clear air flow which can be directed into the detector to prevent smoke particles from settling on critical components of the detector.

Abstract: A method enables digital, serial communication over an interface between an electronic device (102) and a battery (103) attached thereto. The digital, serial communication comprises transmission of bytes (300) consisting of a number of bits. The method comprises the steps of transmitting a byte from a first one of said electronic device and said battery, receiving said byte in the other of said electronic device and said battery, and retransmitting said received byte unchanged. Hereby, it is possible to compare the contents of the returned byte with the contents of the byte originally transmitted, and thus ensure that the byte was transmitted correctly. This simple procedure makes other error handling procedures such as parity bits unnecessary.

Abstract: An alarm system for portable chemical monitors comprising a housing configured for attachment to the portable chemical monitor having a twist lock mechanical connector capable of connecting to the portable chemical monitor, at least three pins mounted within the housing that are capable of inserting into the portable chemical monitor, a circuit board electrically connected to the pins and capable of receiving electrical signals from the chemical monitor, and a ceramic disk supported within the housing having an indicator means for generating vibrational movement that provides a audible sound. A method for monitoring for the presence of chemical agents is disclosed.

Abstract: A vapor sensing device that is sufficiently small and lightweight to be handheld, and also modular so as to allow the device to be conveniently adapted for use in sensing the presence and concentration of a wide variety of specified vapors. The device provides these benefits using a sensor module that incorporates a sample chamber and a plurality of sensors, located on a chip releasably carried within or adjacent to the sample chamber. Optionally, the sensor module can be configured to be releasably plugged into a receptacle formed in the device. Vapors are directed to pass through the sample chamber, whereupon the sensors provide a distinct combination of electrical signals in response to each. The sensors of the sensor module can take the form of chemically sensitive resistors having resistances that vary according to the identity and concentration of an adjacent vapor.

Abstract: The present invention provides a device for measuring air quality. The device includes at least one sensor with a sensor resistance which is converted via signal processing into an output signal, the gas sensing or air content sensing device having its sensor(s) with electrical resistance that is a function of the air quality, such sensors being connected in an astable flipflop circuit arrangement with a first feedback resistor, a second feedback resistor, a capacitor and a comparator--where the first resistor is coupled between the inverting input and output of the comparator, and the second resistor is coupled between the noninverted input and the output of the comparator, and the sensor(s) is/are coupled between a reference potential and the noninverting input of the comparator. The output signal has a period which is related to the sensor resistance.

Abstract: In a biosensor system for detecting trace compounds resulting from a fire or from plants damaged by destructive insects, a live chemoreceptor is provided for sensing the trace compounds, and a semiconductor component is connected to the chemoreceptor for providing sensor signals when the chemoreceptor senses the presence of trace compounds.

Abstract: An atomic absorption photometer includes a microprocessor which is programmed so as to affirmatively create an unsafe condition by lowering the pressure inside the flow route of a combustion improving gas and to check if the gas switch in this flow route indicates this unsafe condition. If it is found that this unsafe condition is not being indicated by the switch, a warning signal is outputted and the use of flame by the photometer is prevented.

Abstract: A gas detector is disclosed which includes a CO sensor and a processor. The CO sensor senses an environmental CO concentration and provides a variable electrical output in response. The processor receives digitized samples of the sensor's electrical output and computes, with each measurement sample, a COHb level of a hypothetical person exposed to the CO concentration sensed. The computation involves determining an equilibrium COHb level for each measurement sample, which is compared with a previously computed COHb level associated with previously measured samples. The previously computed COHb level is updated based on the comparison. When the computed COHb level is above a predetermined danger threshold, the processor preferably causes an audible and visual alarm to be activated to alert any persons present. The gas detector can further include a CH.sub.4 sensor coupled to the processor for independently sensing CH.sub.4 levels such that an alarm is activated when the CH.sub.

Abstract: A polymeric gas sensor utilizes a variety of electrode geometries to generate varied responses to selective gases. The characteristic response to various gases of each electrode geometry permits the construction of a gas sensor having desirable and reproducible characteristic responses to specific gases. The gas sensor array of the invention produces characteristic responses from a plurality of sensors. These responses collectively produce a characteristic response pattern that can be used for the identification of specific gases with pattern recognition techniques.

Abstract: A CO concentration monitoring device operating under the control of a processor periodically checks the CO sensor to insure its ongoing integrity and to issue a distinctive audio signal to a user if sensor integrity has become suspect. The periodic integrity check procedure places a predetermined DC voltage across the sensor. Then, the voltage source is removed leaving the sensor charged as a capacitor such that reading the voltage remaining across the sensor, reading the temperature of the sensor and comparing a temperature adjusted representation of the voltage appearing across the sensor to at least one predetermined representation of a voltage representing a threshold at which sensor integrity becomes suspect. If this condition is determined, a sensor condition alert signal responsive is issued to drive a horn in a distinctive audio sequence (e.g., three 10 millisecond duration pulses spaced at about 500 millisecond intervals).

Abstract: A gas leak and cut-off device is provided including a gas-powered hot water heater having a cylindrical configuration with a circular top face, a circular bottom face, and a cylindrical periphery formed therebetween. The bottom face has a plurality of stanchions coupled thereto and extending downwardly for engaging a recipient surface. A gas input pipe is provided having a first end connected to a gas supply and a second end connected to the periphery of the hot water heater for supplying gas thereto to heat water. A plurality of monitors are each mounted in spaced relationship on the recipient surface with the outboard ends in line with the periphery of the water heater. Each monitor is adapted for generating an activation signal only during the detection of fluid.

Abstract: A new Combination Carbon Monoxide Sensor and Furnace Shut-Off System for automatically terminating natural gas flow to a malfunctioning boiler or furnace which is producing dangerous levels of carbon monoxide. The inventive device includes a carbon monoxide sensor system for detecting carbon monoxide, and a control valve electrically connected to the carbon monoxide sensor system and connected within a gas pipe for controlling the flow of natural gas within the gas pipe. When the carbon monoxide sensor system detects a dangerous level of carbon monoxide surrounding the boiler or furnace, a solenoid is electrically activated for closing the control valve for stopping the flow of natural gas into the malfunctioning boiler or furnace.

Abstract: A gas detector is disclosed which includes a CO sensor and a processor. The CO sensor senses an environmental CO concentration and provides a variable electrical output in response. The processor receives digitized samples of the sensor's electrical output and computes, with each measurement sample, a COHb level of a hypothetical person exposed to the CO concentration sensed. The computation involves determining an equilibrium COHb level for each measurement sample, which is compared with a previously computed COHb level associated with previously measured samples. The previously computed COHb level is updated based on the comparison. When the computed COHb level is above a predetermined danger threshold, the processor preferably causes an audible and visual alarm to be activated to alert any persons present. The gas detector can further include a CH.sub.4 sensor coupled to the processor for independently sensing CH.sub.4 levels such that an alarm is activated when the CH.sub.

Abstract: A gas detection and alarm system and a method thereof for monitoring a predetermined dose of carbon monoxide and other gases in the atmosphere which can be harmful to humans, having a gas detection/alarm device comprising a detection circuit which detects a predetermined dose of a gas such as carbon monoxide, an indication circuit which visually and audibly indicates the dose detection to the user based on the detection circuit, a microprocessor for digitally operating the detection circuit and the indication circuit, a power conversion circuit which converts AC power to DC power without using any transformers and which supplies the converted constant power to the detection circuit, indication circuit and microprocessor, and a housing which compactly houses the detection circuit, indication circuit, power conversion circuit and microprocessor.

Abstract: A binary sensor including a binary sensing circuit, a logic circuit and an adaptive interface card adapted to matingly engage the binary sensor. The binary sensing circuit and logic circuit are operatively coupled for communication with external circuits. The adaptive interface card includes bus network interface circuitry that disables the logic circuit and enables the bus network interface circuitry upon matingly engaging the interface card with the binary sensor. The bus network interface circuitry also becomes operatively coupled with the sensing circuit upon matingly engaging the adaptive interface card with the binary sensor. The bus network interface circuitry of the adaptive interface card provides a means for the binary sensor to communicate with bus networks.

Abstract: A biomedical sensor (20) is formed on a semiconductor substrate (22). Insulated dielectric layers (23, 24) are formed on the face and backside of the semiconductor substrate (22). Metal leads (26, 28) contact the substrate (22) through openings in the dielectric layer (23). The leads (26, 28) are also each connected to a set of interleaved longitudinal contact fingers (27, 29). A pair of contacts (30, 32) are formed on the opposite side of the substrate (22) from the contact figures (27, 29). A conductive biologic sample is placed over the interleaf fingers (27, 29), electrical measurements can be made through backside contacts (30, 32) so resistance measurements can be taken.

Abstract: P-type semiconductor 15 and n-type semiconductor 16 are formed as thick films or spray-coated onto electrodes 13 and 14 on top of substrates 11 and 12, with films of p-type semiconductor 15 and n-type semiconductor 16 being formed in such manner that they are in mutual contact. If a gas to be detected is introduced to the contact region while a bias voltage is being applied between the two electrodes, an output will be obtained in accordance with the concentration of flammable gas components in the gas being detected. In addition, if a film is formed from a material comprising a mixture of particles of p-type semiconductor and particles of n-type semiconductor, the bias voltage can be an AC voltage.

Abstract: Method and apparatus for the detecting hazardous conditions including the hazardous leakage of carbon dioxide gases by detecting spontaneously a plurality of the conditions which are encoded with a different response for each condition; for the detection of hazardous conditions associated with combustion or potential combustion, the detection is of a plurality of gaseous conditions having different chemical and thermal characteristics and the presence of each such condition is indicated; when the detection is of the leakage of fuel gases, a plurality of catalytic units is used, each having a platinum wire extending to a junction with a comparator and bridged by a detector provided with bridge balance and threshold adjustment; periodic heat cleansing is by a multi-terminal bistable oscillator; smoky carbon particles are detected by an ionization chamber connected to alarm circuitry.

Abstract: A low-cost and quick-response type gas-density sensing element is free from positioning error of sensing ambient temperature and gas density and can accurately sense the gas flow even if the environmental conditions sharply change. An output voltage V.sub.1 proportional to an ambient temperature is obtained by heating a sensing element at low temperature and an output voltage V.sub.2 proportional to the ambient temperature and humidity is obtained by heating the sensing element at a high temperature. An output voltage which is proportional to the humidity is obtained by subtracting the voltage value V.sub.1 from the voltage value V.sub.2.

Abstract: A gas detecting method and apparatus for selectively detecting a fuel gas having methane as a main component thereof and an incomplete combustion gas having carbon monoxide as a main component thereof. A low heat capacity, hot-wire semiconductor type gas sensor used has an oxide semiconductor formed mainly of valency-controlled tin oxide and acting as a sensitive section thereof. An inactive to gas combustion, heat resistant, quadrivalent metallic oxide is mixed into the sensitive section. The sensitive section is alternately switched between a fuel gas detecting temperature and an incomplete combustion gas detecting temperature.

Abstract: A CO detector, utilizing periodical temperature change of a metal oxide semi-conductor gas sensor, is equipped with a backup battery. When power cut of a commercial power supply is detected, the detector will be driven by the battery, and the gas sensor will be heated at 50.degree.-100.degree. C. for from 30 seconds to 1 minute and will be kept at room temperature for about 30 minutes. CO is detected by the minimum sensor output after the heating.

Abstract: The invention relates to a gas sensor comprises a precious metal electrode, a semiconductor layer entirely or partly covering the precious metal electrode, a barrier layer having a high potential formed at an interface between the precious metal electrode and the semiconductor layer.

Abstract: A tower light controller comprises logic circuitry that easily connects with equipment used in the production of semiconductor wafers. The tower light controller uses the existing signals in the production equipment, namely a process signal, an alarm signal, left and right cassette present signals, and left and right atmosphere signals, to appropriately drive a light tower comprised of a yellow lamp, a red lamp, and a green lamp. The logic circuitry turns on the green lamp when a product is being run. A yellow lamp is continuously driven when the equipment has wafers that are ready to be unloaded and the yellow lamp is flashed when the equipment is ready to be loaded with wafers. The red lamp is flashed during alarm conditions and is driven continuously when the equipment is placed in a repair or in a preventative maintenance mode. The logic circuitry also comprises an oscillator formed by a series connection of three inverters.

Abstract: A gas monitoring system for use with a gas-fired boiler in a house or the like. The boiler is supplied with flammable gas. The system comprises a transducer, a visible and audible alarm circuit, a digital access terminal, an exhaust fan, and alarm systems, which may be audible or visual. Leaked gas is detected by a gas transducer which produces a voltage indicative of the presence of gas. An electronic circuit, which comprises a comparator, buffer, and power transistor, receives the voltages from the transducer and, when a predetermined level of voltage is received, turns on and closes two switches. One switch enables an audio alarm and provides power to a second switch. The second switch, when closed, joins a source of power to a visual alarm (a bulb), turns on an exhaust fan, and closes a normally open solenoid valve. The solenoid valve is in the gas-conveying conduit. Closing the valve shuts off the unwanted flow of gas. The first switch is provided with a manual reset switch for resetting the system.

Abstract: A sensor device for gaseous hydrocarbons includes two semiconductor oxide-based sensitive elements, one of which is a sensitive reference element and the other a sensitive measuring element, this measuring element being covered with a layer of electrically insulating porous material containing a dispersed noble metal. The two sensitive elements are formed by silk-screen processes, are connected to an electronic signal comparison system, and are maintained at different temperatures when in operation. The sensor has improved selectivity in determining gaseous hydrocarbons, in particular methane, even if high concentrations of interfering gases such as ethanol are present.

Abstract: A fire sensing method and apparatus for detecting a fire based on the detection of a hydrocarbon gas produced before fire ignition and the detection of a second fire indicating phenomenon. Such other phenomenon may comprise the detection of temperature, radiation or combustion product gases. The detection of hydrocarbon gas may generate a pre-alarm condition which permits the use of higher sensitivity conditions for the second fire indicating phenomenon.

Abstract: A new and improved gas detection, concentration and warning apparatus is disclosed which includes a tin dioxide semiconductor gas sensor operated with a load resistor of a preselected value and power source for producing reliable and consistent gas concentration voltage output for either a voltmeter having a dial calibrated to read the voltage and indicate corresponding gas concentrations for a portable work site apparatus or to trigger and threshold inputs to a 555 timer where first and second state outputs are connected to either a sound alarm for a home apparatus or to light or sound or both alarms located in a vehicle dashboard for a natural gas fueled vehicle. For vehicle use, multiple gas sensor circuits are used with their probes located under the vehicle hood and in the supply tank compartment (trunk).

Abstract: The present invention relates to a device for indicating toxic substances in air that is supplied to accommodation used for personnel, preferably the cab of a motor vehicle, this having error compensation for humidity and temperature in one or a plurality of semiconductor gas sensors that are used, in which connection the sensor heating voltage is controlled to provide constant heating output and the sensor temperature pick up as well as the necessary amplifier (control stage) used to generate the temperature-varied heating voltage are arranged in a common housing, and that in the area of the sensors this housing is perforated.

Abstract: A method for the direct presentation of a differential measured quantity, in particular, a differential gas concentration measurement, in terms of its correct physical unit is disclosed. A characteristic curve representing the output of a gas sensor detector as a function of gas concentration is obtained in an absolute coordinate system. A reference level at which the differential measurement is to occur is defined on this characteristic curve by a defined input or, respectively, output value. This reference level defines the origin of a differential coordinate system from which the differential measurement may be directly ascertained.

Abstract: A reactive gas detection system provides early warning of gas emissions that often occur in developing fire conditions in environments such as telephone system central offices where halogenated substances, for example polyvinyl chloride wire insulation and brominated fire retardant materials, are prevalent. Multiple microbalance detectors (122) comprising quartz crystal oscillators coated with a layer of zinc or zinc compound are distributed about a premises and the rate of change of crystal oscillation frequency is cyclically monitored by a frequency counter (130) under control of a data processor (112). The detectors are specifically reactive to the halogen acid gases emitted during pyrolysis of the noted substances and exhibit a significant differential frequency change in the presence one or more of these gases well in advance of the outbreak of flame, smoke, or other normally detectable combustion products.

Abstract: A circuit for the evaluation of a signal produced by a semiconductor gas sensor provides a reliable control for manipulating a recirculated air valve in motor vehicles and their air-conditioning systems and includes a voltage divider connected with an integrator having a time constant bigger than time needed for reaching a peak of noxious gases outside of the motor vehicle.

Abstract: Chemical microsensors are fabricated by applying dithiolene transition metal complexes as thin films to chemiresistor devices using the Langmuir-Blodgett technique. The thin films interact with ambient gases and change electrical conductivity upon exposure to a particular gas or vapor. The film material determines the chemical sensitivity and selectivity. The degree of current change depends on the particular gas or vapor and its concentration. These compounds are different in structure and electrical conductive response to gas or vapors than previous materials used for chemical microsensors. This invention is particularly suited for hydrazine detection.

Abstract: The present invention is a safety system for a gas operated appliance in a vehicle. The system includes means for generating an electrical signal, such as a pre-determined voltage. The system also includes means for interrupting this electrical signal. One such means is a gas sensing means which is designed to interrupt the electrical signal in response to sensing gas. Another such means is an inertia switch means which interrupts the electrical signal in response to detecting a rapid changes in vehicle inertia or vehicle orientation. Yet another such means is a high temperature switch means which interrupts the electrical signal in response to detecting an elevated temperature in an area near said appliance. Finally, the system includes an emergency kill switch means for manually interrupting the electrical signal. The system further includes a fuel tank and a gas line between the fuel tank and the appliance.

Abstract: A gas sensing thick film is positioned on an insulating substrate in contact with a pair of electrodes. A non-porous glass layer surrounds the film to stabilize it on the substrate. A heating element maintains the film at a preselected elevated temperature. The gas sensing thick film has a response characteristic for a preselected target gas to be detected which is enhanced by impregnating the film with platinum or palladium chlorine free compounds. The response characteristic of the gas sensing film is further increased by promoting combustion of interference gases on an outer filter layer fabricated of either conductive or nonconductive material. The incorporation of an insulating material between the gas sensing film and the outer filter layer also serves to increase the relative response of the gas sensing film to a preselected target gas.

Abstract: A tin oxide carbon monoxide sensor is operated in a manner to exclude effects of ambient temperature and humidity. Resistance of the sensor is measured at a lower temperature and again at a higher temperature. The target gas concentration is determined as a function of the first and second resistances, thereby cancelling the effects of humidity and ambient temperature.

Abstract: An element for detecting internal faults in an insulating gas charged electrical apparatus comprises a substrate disposed in the electrical apparatus charged with an insulating gas, a pair of electrodes disposed on the substrate, and a thin metal film covering the pair of electrodes and the exposed surface of the substrate. This film is capable of producing fluorides with low conductivity upon reacting with a decomposed gas produced by internal faults of the electrical apparatus. Since the thin metal film exhibits high response characteristics readily in reaction with even a trace amount of a decomposed gas, it is possible to promptly detect faults occurring in the electrical apparatus, such as a partial discharge or local heating. In addition, a device for detecting internal faults in an insulating gas charge electrical apparatus using the internal fault detection element utilizes an optical signal for transmitting signals.

Abstract: A vapor or gas detector (12) that forms an element of a vapor or gas detecting and alarm system (30). The detector in one of its embodiments is configured as a three-section dynamic junction (16) consisting of a resilient substrate (22) having a resonant mechanical element (18) attached to its back and an absorbate (20) to its front. When no toxic vapors or gases are present, the element (18) is under a no-strain, no deformation condition and emits a first frequency signal. When a toxic vapor or gas is present, the absorbate (20) absorbs the gas or vapor which causes the substrate (22) to deform and, in turn, causes the element (18) to deform and emit a second frequency signal. This second frequency signal is applied to the system (30) where the signal, through a series of electronic circuits is processed. The processed signal activates a lamp (44a) and an audible alarm (44a) indicating that the detected vapor or gas has exceeded a preselected toxicity level.

Abstract: A combustible gas detector having a transformer, a gas detector, a buzzer, a capacitor connected in parallel with the buzzer, an electronic switch, and two resistors. The gas detector has a resistive element which varies in the presence of a combustible gas. The resistive element and one of the resistors form a voltage divider which produces a potential triggering the electronic switch to energize the buzzer upon the detection of a combustible gas. The capacitor modifies the wave form across the buzzer causing it to produce a unique cricket-like sound.

Abstract: Lightweight, compact apparatus for detecting sudden changes in the concentration of at least one selected gas provides a warning when said gas concentration increases suddenly. In one embodiment, a chemically sensitive field effect transistor provides a sensing signal two amplifiers having different overall gains and widely different time constants. Detection of sudden gas concentration changes causes the relative magnitudes of the amplifier output signals to be inverted triggering a warning. The apparatus may occupy less than 1.25 cubic inches and weigh less than 4 ounces so that it may be worn by an individual throughout his work place.

Abstract: A preferred semiconductor gas sensor of this invention features a gas interaction site comprising a gas sensitive semiconductor thin film and means for heating the film to an operative temperature. The thin film and heating means are carried upon a region of a substrate that is etched opposite the site to reduce the thickness of the region and thereby reduce heat flow from the region into a surrounding region.

Abstract: An alarm and control system for semiconductor factories or the like includes, at locations where poisonous and inflammable gases such as silane gas are used as in the manufacturing process of semiconductors, gas detectors to detect the leakage of the treatment gases and fire detectors to detect products of combustion of the treatment gases, and these detectors are adapted to cause, upon any changes in the output state of either of them, an alarm to issue and a protection device such as a fire distinguishing device as well as the manufacturing process to be controlled.

Abstract: A method is disclosed for forming a chemically sensitive field-effect transistor having a suspended gate which enables the uniform and reproducible manufacture of such devices. Controlled uniformity and device response is provided by this method which makes the field-effect transistors suitable for use as sensors, alarms and analyzers for gases. A method of regenerating a chemically sensitive field-effect transistor having a suspended gate is also disclosed.

Abstract: An alarm and control system for semiconductor factories or the like wherein poisonous and inflammable treatment gases such as silane gas are used as in the manufacturing process of semiconductors, etc. is disclosed. Gas detecting means are provided at locations where the treatment gases are used, the gas detecting means utilizing metal oxide semiconductors containing platinum black as a detecting element for detecting the leakage of the treatment gases.

Abstract: Gas sensor consisting of a housing which is divided into two compartments 3 and 4 by means of a fluid filter 2, e.g. a bed of activated charcoal. Compartment 3 has an inlet channel 5 and contains a first gas-sensitive semiconductor 6, the measuring device. Compartment 4 has an outlet channel 7 and contains a second gas sensitive semiconductor 8, being used as a reference device. The value of the electric resistances of devices 6 and 8 will increase or decrease when the compartments 3 and 4 contain either an oxidizing or a reducing gas. The sensor is used in a gas detection system in which an electronic circuit which follows determines the ratio between said resistances and the ratio of the reference device and a reference resistance. These ratios are subsequently compared to certain limiting values, and when these values are exceeded, a detection signal will be produced.