Abstract: A gas sampling device including a chamber assembly formed of a chamber base having a chamber top mounted thereto is disclosed. A gas sensor is mounted to the chamber base in fluid communication with a gas flow passage therethrough. A motor is mounted to the lower surface of the chamber base and has a shaft extending through the chamber base. A fan is mounted onto the motor shaft within the chamber housing. An inlet flow passage extends through the chamber top above the center of the fan and an outlet flow passage extends through the chamber top above the gas flow passage. The fan and the chamber top are provided with a particular configuration to provide for efficient and smooth flows of gas through the housing and to the sensor.

Abstract: The present invention is directed towards a low power, solid state gas sensor and method of making the same. The sensor comprises a heating element formed from a wire coiled about an axis, a sensing whisker placed inside the heating coil substantially in plane with said axis, and a metal oxide semiconductor material whose resistance varies with the object gas concentration. The gas sensors of this type operate at less than 150 mA. In addition, gas sensors of the present invention exhibit a substantially linear response over a significant concentration of the object gas.

Abstract: An electrochemical cell for use in gas detection includes a cell body having an electrolyte cavity and a separate sensor cavity. The sensor cavity holds stacked sensor elements including a counter electrode, electrolyte mat, reference electrode and sensing electrode. A wick draws the electrolyte from the electrolyte cavity to the electrolyte mat. The sensing electrode closes off the sensor cavity and seals the counter and reference electrodes therein. The only gas which contacts the counter and reference electrodes is that which passes through the sensing electrode or is generated by the counter electrode and becomes dissolved in the electrolyte.

Abstract: A transmitter circuit adapted to be connected to a sensor and generate a 4-20 milliampere signal proportional to the output of the sensor includes a first amplifier which is connected to the sensor and has an output voltage proportional to the sensor output voltage. A predetermined reference voltage is supplied to a reference input of the first amplifier. A second amplifier housing an output voltage responsive to a difference between its input voltages, has its output connected to the gate of an output transistor, preferably a fluid offset transistor. An output resistor is connected between the positive power supply and the source of the output transistor. The output of the first amplifier is supplied to the positive input of the second amplifier and the voltage at the source of the output transistor is supplied to the negative input of the second amplifier. The output current for the transmitter is generated at the drain of the output transistor.

Abstract: Platinum black is electrochemically plated onto a conductive substrate, such as a platinum electrode, by positioning a counter electrode and the conductive substrate in a platinum(IV) ion plating solution. An electric current is passed through the counter electrode, substrate and plating solution for a predetermined period of time. The plating solution and conductive substrate are subjected to ultrasonic agitation while the plating is carried out. The plating solution preferably includes chloroplatinic acid and lead ion.

Abstract: A trimode gas detection instrument having three operating modes, one which monitors the level of combustible gases, a second which monitors oxygen, and a third which monitors the displacement of air by an unknown gas. Only two sensors are used, a combustible gas sensor and an oxygen sensor. A switch selects the input to a readout so that the user can quickly observe the concentration readings in any of the three modes. In the depletion mode the readout is calibrated in relation to the inverse of the normal concentration of oxygen in air--i.e., zero depletion corresponds to an oxygen concentration of 21%. In the event that an unknown gas displaces air in a sample atmosphere, concentration of the unknown gas appears on the readout, such that zero oxygen corresponds to a concentration of 100% unknown gas.

Abstract: A bias circuit (13) for an electrochemical fuel cell (15) serving for example as a carbon monoxide or hydrogen sulfide detector, including an operational amplifier tied to the anode and reference terminals (21,23) of the fuel cell (15), and a zener diode (50) arrangement for maintaining a predetermined voltage drop between the output and negative inputs of the operational amplifier (33).

Abstract: An apparatus for the detection and measurement of an object gas is disclosed. Such an apparatus comprises a sensing electrode having a catalytic surface, a counter electrode having a catalytic surface, an electrolyte in electrical contact with the sensing electrode and the counter electrode, a reference electrode in contact with the electrolyte and the sensing electrode, a means for supplying an electrical potential between the sensing electrode and the reference electrode and a means for measuring the current flow resulting from the reaction of the object gas with the sensing electrode by way of the sensing electrode substrate to the counter electrode substrate. The substrate, which supports the catalytic sensing electrode and counter electrode materials being electrically conductive carbon or graphite, which allows the electrons generated at the sensing electrode catalytic surface to be removed through the substrate instead of from the surface.

Abstract: The present invention discloses the use of gold oxide as a catalyst for use in a hydrogen sulfide gas detector. The gold oxide catalytic surface being supported on an electrically conductive substrate; thereby allowing the flow of electrons between the anode and the cathode to occur between the substrates of the electrodes instead of the catalytic surfaces. This will reduce the amount of catalytic material required to form the electrode, and will not require that the catalytic surface be an electrical continuum.