Abstract: A composite fire sensor comprising a first sensor element sensitive to a change in incident infrared rays, a second sensor element having a variable electric conductivity according to gas absorption/desorption, at least one comparator for combining the outputs of the first and second sensor elements, and a delay circuit for delaying the output of at least one of the comparators. Predetermined reference voltages are supplied to the comparators.

Abstract: A gas detecting apparatus incorporates a number of gas detecting elements which react with a variety of gases and exhibit gas sensitivities differing from one another in dependence on the gas species. The detection patterns obtained by quantitizing the detection outputs of the gas detecting elements are compared with a plurality of standard patterns prepared previously for assumed combinations of gas species and concentrations thereof. On the basis of the standard pattern which is same or most similar to the detection pattern, the gas species is identified.

Abstract: A gas sensor comprising a sintered piece composed of tin oxide, at least one of lanthanide oxides and at least one of IVa group element oxides. The sintered piece may be covered or coated with a porous layer of a ceramic material such as silica, alumina or silica-alumina.

Abstract: A gas detecting apparatus is disclosed in which detection outputs from a plurality of semiconductor gas detecting elements different in gas detection characteristic from each other and previously-obtained characteristic values of the semiconductor gas detecting elements for a mixed gas are subjected to operational processing to detect one or more specified constituent gases contained in the mixed gas, and in which when the specified constituent gas is detected, the detection information is announced by some means, and also the supply of gas is stopped or a supply gas is diluted.

Abstract: A sensor element responding to gases and/or vapors is heated in at least two temperature cycles continuously from a starting temperature value to an upper temperature value in accordance with a predetermined pattern which is optimized for selective gases. The temperature is lowered to the starting temperature value in accordance with the same or a different pattern. During the temperature cycles a signal which depends on the composition of the gas or vapor atmosphere delivered by the sensor element is compared in an electronic evaluation circuit to stored values which are characteristic for the presence of selective components in the gas and/or vapor.

Abstract: A system for sensing and annunciating the presence at any one of a plurality of locations of accumulations of potentially hazardous gaseous and vapor mixtures prior to their reaching a lower explosive limit thereof. The system has particular applicability to aircraft, and has a number of advantageous features such as adjustable annunciator set points which are settable between relatively wide lower explosive level limits, compensation in the sensor circuitry for temperature variations, built in diagnostic and test features, and a circuit design wherein multiple sensors at multiple locations are operable independently of each other.

Abstract: A gas detector for detecting the leak of fuel gases, such as hydrogen gas, methane gas, butane gas, with improved reliability in detecting the gas leak. Said gas detector includes a main gas sensing element showing the change in resistance to target gases, such as methane, butane, hydrogen, as well as to non-target gases, such as alcohol, steam, smoke; an auxiliary gas sensing element showing change in resistance rather to non-target gas than to target gas; the first comparator receiving the output induced by resistance change in main gas sensor, as input; the second comparator with reference voltage set at lower level than that for the first comparator; and a gate circuit for blocking the alarm driving signal of the second comparator by the output induced by resistance change in auxiliary gas sensor. The output obtained from either said gate circuit or the first comparator is used for alarm driving signal of alarm circuit.

Abstract: A two stage process for interrogating a detector of the concentration of combustible gas in an atmosphere. In a first stage, the detector is supplied with a low voltage and the supply is cut and an optional alarm is sounded if a positive signal has been detected. In a second stage, if the signal detected in the first stage is negative or zero, then the detector is supplied with a second, higher voltage. The signal is compared to a predetermined range and, if not within that range, an optional alarm is sounded. A device to apply the process comprising a detector, an amplifier of the signal issued by the detector, a voltage reducing circuit, and a switch that controls the voltage reducing circuit slaved by a discriminator to the sign and/or to the maximum amplitude of the signal output by the amplifier. Application of the process and device to the detection of the concentration of methane.

Abstract: A gas detection device and a method for detecting a gas where gas information including concentrations of gas components in a mixed gas, concentration, presence of specific gas components and the like is detected by measuring, e.g., the output voltages of a plurality of gas sensors having different gas selectivities. The gas selectivities, as a characteristic constant of the specific gas sensor, was previously determined. The measured output voltages and gas selectivities are then used for solving plural simultaneous equations for gas concentrations.

Abstract: A gas detector comprising a main gas sensing element showing the resistance change to both the detection target gases, such as methane, butane, hydrogen gases, and non-target gases such as alcohol steam, smoke; an auxiliary gas sensing element showing the resistance change primarily to non-target gases along; the first comparator to which the output based on the resistance change of main gas sensing element is received as input in parallel form; the second comparator with lower reference electric power than that of the first comparator; a gate circuit to cut off the alarm actuating signal from the second comparator by means of output induced by the resistance change of auxiliary gas sensing element. Either the output from said gate circuit or the output from said first comparator is used for alarm actuating signal of alarm circuit.

Abstract: A metal-oxide semiconductor, which is heated to different temperatures, is used in conjunction with an electronic circuit for reducing false alarms caused by spurious gases in gas warning installations and for determining the composition of a gas mixture. The temperature of the metal-oxide semiconductor, after reaching a predetermined value (T), is altered by an amount (.DELTA.T) either towards the positive or negative side or towards both the positive and negative side, respectively. The thus caused change in the conductivity of the metal-oxide semiconductor is evaluated in a comparator and in circuits for the different peak values of the gas components.

Abstract: Alarm-indicating gas detection apparatus including a first semiconductor gas-sensing element having one electrical property which varies significantly with increasing concentrations of a first undesirable gas and less significantly with increasing concentrations of a second undesirable gas and a second semiconductor gas-sensing element having the same electrical property which varies significantly with increasing concentrations of the second gas and less significantly with increasing concentrations of the first gas. The electrical property of both gas-sensing elements tends to vary similarly with age and with changing conditions such as temperature and relative humidity. A compensation system is used to cancel out errors due to variations in the electrical property. Threshold circuits are used to distinguish between first and second undesirable gases and to generate alarm signals.

Abstract: Improvements in a gas detecting system utilizing a filament-heated gas sensor displaying measurable resistance characteristics which vary with the concentration of selected gases within the atmosphere in the vicinity of the sensor inhibit the production of gas detection indications automatically during the initial activation of the system while the sensor element is stabilizing and further inhibit the production of short staccato alarm indications produced by inherent small changes in the characteristics of the sensor brought about by thermal drift.

Abstract: An improved thick film stannic oxide sensor is disclosed whereby the sensitivity of the sensor to CO is enhanced by the addition of a rare earth oxide to the sensor composition and the catalytic reactivity of the sensor, when contacted by a gas containing a reducing constituent, i.e., H.sub.2 or CO, and oxygen, is enhanced by employing RuCl.sub.3 or PtCl.sub.2 as a catalyst.

Abstract: A gas sensing signaling system is provided in which a plurality of gas sensing units are connected over cables with a central station. To permit establishment of threshold levels such that false alarms are rejected while the system still remains sensitive to dangerous conditions and to permit ready supervision and testing of said system, a central station is provided in which timing circuits are included which start the time interval upon sensing of an alarm condition above a lower, or warning threshold level. If the lower warning level signal persists for the timing interval--for example for about one-half minute, a warning signal is given. A higher level signal generates an alarm signal, either immediately or after a much shorter time delay. The circuit includes self-holding circuitry so that, once a sensing unit transmits a sensing signal which persists beyond the previous predetermined warning or alarm time duration, the central station will indicate the respective conditions until manually reset.

Abstract: A gas leakage detector comprising a solid state gas sensor having a sintered metallic oxide block which changes thermal conductivity by chemical adsorption thereto and a wire for transforming thermal conductivity charges into an electric signal. A suction pump draws gas through a gas intake path to the gas sensor. A voltage-frequency converter generates a pulse frequency that is a function of the gas sensor voltage. An alarm indicator including sound and/or light is controlled to pulse by the output pulse of the voltage frequency converter.

Abstract: A fume detector including a gas sensor having a heater element and a variable impedance element associated therewith whose impedance decreases in the presence of toxic gases or fumes, or a decrease of free oxygen in an atmosphere being monitored. A load resistor in series circuit with the gas sensor and a pair of series connected potentiometers in parallel circuit with the gas sensor and the load resistor form a Wheatstone bridge. A first voltage comparator connected to one of the potentiometers and a reference voltage provides a signal when the supply voltage decreases below a predetermined level. A second voltage comparator connected to the other potentiometer and a junction between the gas sensor and the load resistor provides a signal when the gas sensor fails in the open circuit condition. A third voltage comparator connected across the bridge provides a signal when a toxic gas condition exists.

Abstract: In a gas sensor circuit having a semiconductor gas measuring sensor such as a Taguchi, a variable gain transconductance amplifier is interconnected between the gas measuring sensor and a conventional differential amplifier so that the circuit's output voltage appears as a linear function of the gas concentration being measured.

Abstract: A gas detector (11) provides a comparator (22) having a plurality of inputs to provide a simplistic but yet reliable sensing sequence for detecting a contaminated gas such as carbon monoxide. A first input (55) is supplied from an enable circuit (41) which disables the comparator (22) for a predetermined period of time to prevent operation of an associated alarm (33) to permit a heater (14) of a gas sensor (12) to be initially energized to properly condition the associated gas sensing electrodes (13). A second input (16) is supplied from the gas sensor (12) to continually monitor the carbon monoxide concentration to provide an alarm (33) when sensing a high level of gas contamination. A third input (34) provides a latching circuit to continually activate the alarm (33) until the power input (15) is de-energized. A fourth input (27) provides a predetermined reference voltage to the comparator (22).

Abstract: An alarm system responsive to a predetermined concentration of gaseous hydrocarbon in an area. A gaseous hydrocarbon responsive variable resistance element having a heater has resistance characteristics that are relatively stable upon energization of the heater beyond an initial heating period, decrease from the relatively stable value as a function of the concentration of gaseous hydrocarbons in the vicinity of the sensor, and decrease to an initial action resistance value substantially below the stable value during the initial heating period. First and second switching devices connected in series with a power source produce an audible alarm signal with both in their conductive condition.

Abstract: A methane monitor is disclosed that has at least one removable and replaceable sensor interchangeably inserted into a receptacle located on the outside wall of the monitor. A thumb operated latch attached to the sensor is used for connecting the sensor into the receptacle.

Abstract: A variable resistance gas sensor controls the output frequency of a varia frequency tone generator. A tone decoder monitors the output frequency of the tone generator. When the gas concentration attains a predetermined threshold value, the tone decoder produces an output signal which activates a latch circuit to energize an alarm device. The latch circuit continues to energize the alarm device even after the gas concentration is reduced below the threshold value until manually reset.

Abstract: A combined microwave and electric heating oven comprises a gas sensor disposed in an exhaustion duct for detecting an exhaustion gas concentration, and a thermistor disposed in the exhaustion duct for detecting an exhaustion air temperature. A control circuit is connected to receive output signals derived from the gas sensor and the thermistor for terminating a cooking operation when both of the exhaustion gas concentration and the exhaustion air temperature exceed preseleted reference levels, respectively.

Abstract: A combined microwave and electric heating cooking apparatus comprising a magnetron for microwave cooking purposes, a sheath heater for electric heating cooking purposes, and a cooking control circuit for controlling operations of the magnetron and the sheath heater. A gas sensor is disposed in an exhaustion gas path for detecting the concentration of the gas generated from a foodstuff. When an output signal of the gas sensor indicates that the gas concentration reaches a preselected value, the cooking control circuit develops a control signal for terminating the cooking. Selection switches are provided for determining the above-mentioned preselected value in accordance with the kind of the foodstuff to be cooked.

Abstract: A gas component detector for detecting a gas component in the exhaust gases includes a detector element of a metal oxide whose electrical resistance value varies suddenly depending on the gas component. The detector element is held on an electrically insulating and heat-resistant holding body and furthermore, the detector element is enclosed by a catalyst carrier body which is fixed to the holding body by an inorganic bonding adhesive. Since the catalyst carrier body is of a porous heat-resistant metal oxide, the exhaust gases to be detected are permitted to pass through the catalyst carrier body and the gas component is oxidated by the aid of a catalyst material carried on the carrier body. The environment of the detector element thus becomes a weak reducing environment thereby preventing the detector element from being reduced and deteriorated.

Abstract: A microwave oven includes a magnetron, a blower fan system, and a gas sensor for detecting an exhaustion gas concentration developed from an oven cavity. When the exhaustion gas concentration exceeds a preselected value while an actual cooking operation is conducted, the gas sensor develops a first detection output to complete the actual cooking operation. While the actual cooking operation is not conducted, the gas sensor functions as a gas leak alarm sensor. When an ambience gas concentration shows an abnormal value, the gas sensor develops a second detection output to announce a dangerous gas leakage. While the actual cooking operation is not conducted, the blower fan system is intermittently energized to introduce the ambience air toward the gas sensor for monitoring purposes.

Abstract: A method and apparatus for automatically recalibrating a leak detector. A gaseous impurities is detected by means of a corona discharge. This discharge is sampled and a signal that is a function of the corona discharge level is stored. Subsequent corona discharge levels are compared to the stored signal; and an alarm signal is produced when the subsequent discharge levels exceed the stored value by more than a predetermined amount. To recalibrate the circuit a new signal is stored representative of the corona discharge level at that time. Subsequent corona discharge levels are then compared with the newly stored signal.

Abstract: A failure sensor for a gas detector comprises a direct current amplifier having a feed-back path between its output and its input. The feed-back path includes a negative feed-back circuit. A connection is provided in the feed-back path for connection to a gas detector and is arranged to influence the feed-back factor. There is also provided a sensor for sensing differential voltage between the connection and the feed-back path and the output of the amplifier and for providing an output signal indicative of a fault condition where a predetermined differential value occurs.

Abstract: A gas sensor unit designed to indicate the presence of hydrocarbon vapors but be insensitive to carbon monoxide. The unit comprises two TGS sensors, one covered by a semi-permeable membrane and the other uncovered; the uncovered sensor responds to both crude oil and carbon monoxide, the covered sensor responds only to carbon monoxide. In one embodiment, the two sensors are connected in series; the total response of both sensors and the difference in response between the two sensors are measured, and changes in the parameters indicate the presence of an oil spill. In another embodiment, each sensor's output is compared with its reference voltage; if the uncovered sensor has an output that is higher than its reference while the covered one does not, the presence of an oil spill is indicated.

Abstract: A vapor sensitive resistor, or switch, is connected in a bridge network having the input connected to the battery of a marine engine. A window signal comparator includes a high limit operational amplifier and a low limit operational amplifier, each have a first input connected to the opposite sides of a reference resistor in the bridge network to establish relatively high and low reference voltages and second inputs connected in common to the sensing resistor. The amplifiers include a positive feedback and two outputs are connected to an "OR" logic gate which is connected to drive a two-stage transistor amplifier wholly on or off. An alarm device is connected in series with the amplifier to the battery. A test switch varies the circuit connection of the vapor sensitive resistor to simulate a high or low limit condition and thereby test circuit operation.

Abstract: A gas detecting element having a high gas selectivity which comprises an N-type metal oxide semiconductor, 0.005 to 8% by weight, based on the metal oxide, of at least one noble metal catalyst selected from the group consisting of platinum (Pt), palladium (Pd) and rhodium (Rh) and phosphorus 1.5 to 30 times as much as that of the noble metal or 0.05 to 30 times as much as that of palladium where palladium alone is used as the noble metal catalyst.

Abstract: A recreational vehicle safety system includes two independently operable automatic shutoff valve assemblies. One valve assembly is attached directly to the recreational vehicle's appliance high-pressure fuel tank in such a manner as to be operable in all conceivable crash situations, and the other is connected downstream from the appliance fuel line's high-pressure regulator and is designed to close off the fuel flow when a fuel line breaks or small gas leaks are present, such as when an appliance pilot light goes out. Provided also with these valve assemblies are a gas sensor and warning light and audible alarms located about the recreational vehicle to alert campers to potentially dangerous malfunctions. Electrical and manual resets are provided for the safety system, so that the recreational vehicle's appliances can be made operable again if a malfunction occurs in the wilderness, remote from needed tools and expert mechanical assistance.

Abstract: A sensing system for use in a garage or other similar enclosure having an automatic door operator for automatically opening a garage door responsive to a lack of sufficient oxygen therein including a gas detector located within the enclosure responsive to actuate a detection relay which in turn will close a normally open detection switch, the closing of the detection switch will normally cause operation of the door operator to allow oxygen to enter into the enclosure through the door opening, the detection switch being located in a door opening control circuit which includes therein a first limit switch which is open whenever the door is open in order to prevent actuation of the door operator when the door is already open, the door opening control circuit also including a delay clock and delay switch which will be normally closed to allow operation of the door operator, this system also including a time delay circuit with a second limit switch therein which is adapted to be normally open and to close only whe

Abstract: A sensor for the quantitative determination of reduction of a gas in which a thin tungsten oxide film detector element includes means for providing a specificity for the gas to be detected with respect to other gases. If ammonia is to be detected, a platinum catalyst is utilized. If hydrogen sulfide is to be detected, tungsten trioxide is used in the film.

Abstract: A semiconductor sensor element having two filaments of a noble metal, preferably platinum, embedded in spaced apart relation in a body of titanium oxide. One of the filaments serves as a sensing filament. The other filament is supplied with current at a high voltage, suitably about 100 volts. The resistance of the sensing filament increases sharply in the presence of gaseous chlorine or chlorine compounds, and this change in resistance is used to actuate an alarm or the like.

Abstract: A gas sensor incorporating a sensor element of the heated semi-conductor type has a heater for the element connectible to a variable power source, the output of which is responsive to the concentration of gas under test.

Abstract: A gas leak-detecting apparatus which comprises an alarm circuit; a gas-detecting circuit electrically separated from the alarm circuit and provided with a gas-sensitive element prepared from an oxide semiconductor; and a contactless coupling circuit for operating the alarm circuit by an output from the gas-detecting circuit.

Abstract: The instrument uses a semiconductor gas sensor element energized with a regulated voltage source and placed in the atmosphere to be tested to generate a signal representative of the concentration of natural gas in the air. A meter displays the signal to determine whether the area is hazardous, and a variable repetition rate blocking oscillator feeding a speaker is responsive to the signal for generating an audible tick rate useful in locating a leak. The instrument is light-weight, portable, easy to use and intended to comply with industry standards as an intrinsically safe instrument.

Abstract: A thermochemical combustible gas detector having a resistor bridge including a thermistor which is sensitive to combustible gases and a thermistor which compensates the effects of unmeasured parameters and components upon the former thermistor. The supply diagonal of the bridge is connected to a power source via a compensating voltage stabilizer having an adjusting link and two amplifier-comparator links one of which is auxiliary. The detector further includes two conventional auxiliary resistors which are interconnected in series and form an additional resistor bridge with the thermistors of the main bridge. The input of the first amplifier-comparator link is connected to the measuring diagonal of the main bridge. The input of the auxiliary amplifier-comparator link is connected either to the measuring diagonal of the additional resistor bridge, or to one of the auxiliary resistors.

Abstract: A detector for smoke and/or selected gases includes a sensor means to which the smoke or gas is applied. The sensor is connected at one terminal to ground, the other terminal going through a current meter, through a control potentiometer to a selected positive DC voltage. A potential detector is connected at a selected point in the potentiometer so as to determine when a selected magnitude of current is flowing through the sensor. The output of the detector goes through an alarm control means, and an alarm, which is sounded whenever the current through the sensor is greater than a selected minimum value. The system also includes a scanning detector system where a plurality of separate sensors are used, each in a separate location.

Abstract: In a gas detector circuit a semiconductive detector, such as a Taguchi detector, is disposed in gas communication with the gas to be detected. The detector has a sensing resistor incorporated therein with a value of resistance that changes in accordance with the concentration of the gas constituent being detected. This type of detector provides an output signal with a temperature dependence caused by the temperature coefficient of the resistance of the resistive detector with a negative sign. The temperature dependent output signal derived from the detector is fed to one input of a differential amplifier for comparison against a second input to derive an output signal which is fed to an alarm and/or meter and/or recorder. A feedback signal portion of the output of the differential amplifier is fed back to the second input of the differential amplifier, as a feedback component of the second input, via the intermediary of a gain control resistor.