An ion chamber provides a current representative of its characteristics as affected by external conditions, e.g., clean air or smoke. A direct current (DC) voltage is applied to the ion chamber at a first polarity and the resulting current through the ion chamber and parasitic leakage current is measured at the first polarity, then the DC voltage is applied to the ion chamber at a second polarity opposite the first polarity, and the resulting current through the ion chamber and parasitic leakage current is measured at the second polarity. Since substantially no current flows through the ion chamber at the second polarity, the common mode parasitic leakage current contribution may be removed from the total current measurement by subtracting the current measured at the second polarity from the current measured at the first polarity, resulting in just the current through the ion chamber.

Disclosed is a photoionization gas sensor including an ultraviolet generating module having a first substrate, a second substrate, and a third substrate sequentially coupled in a vertical direction, and configured to generate ultraviolet by applying an electric field to a noble gas filling a first cavity, the first cavity formed in a central portion of the second substrate, and a measuring module configured to collect an electrical signal, the electrical signal being generated such that an electric field is applied to a passage, through which gas ionized by ultraviolet passes, so as to allow the ionized gas to come into contact with an electrode, thereby having a small volume and being operated at a low voltage.

Disclosed is a photoionization gas sensor including an ultraviolet generating module having a first substrate, a second substrate, and a third substrate sequentially coupled in a vertical direction, and configured to generate ultraviolet by applying an electric field to a noble gas filling a first cavity, the first cavity formed in a central portion of the second substrate, and a measuring module configured to collect an electrical signal, the electrical signal being generated such that an electric field is applied to a passage, through which gas ionized by ultraviolet passes, so as to allow the ionized gas to come into contact with an electrode, thereby having a small volume and being operated at a low voltage.

Provided is a discharge ionization current detector that is highly durable and yet can be produced at a low cost. An electrode structure 19 consisting of a dielectric-coated metal tube 16, with an insulator-coated metal wire 18 included therein, is inserted from above into a first gas passage including a dielectric tube 10. The metal tube 16 is connected to the ground on the upstream side of the first gas passage. One end of the metal wire 18 is extracted from the upstream side of the first gas passage to the outside and connected to a bias power source 33. An area which is not covered with the insulator is provided at the other end of the wire 18. This area is arranged in a second gas passage, which extends from the downstream end of the first gas passage. A metal electrode consisting of a flanged metal tube 28 is placed in the second gas passage and connected to an ion current detecting circuit 34. In the present configuration, the second gas passage, which should be heated to high temperatures, has fewer portions at which metallic parts are in contact with insulating members. This is advantageous for improving the durability of the device and reducing the used amount of expensive, highly heat-resistant sealing members and/or insulating members.

A gas-equilibrated, volatile-in-water detector comprises a gas-sensing chamber having an orifice closed by a hydrophobic, vapour-porous membrane, typically PTFE, sealed to the periphery of the orifice. Membrane is also sealed to an external wall of a surrounding enclosure and forms an entry point to a second gaseous enclosure external of the gas-sensing chamber. A PID or similar sensor generates a measurable current or voltage in response to the partial pressure of the analyte within the gas-sensing chamber without the sensor significantly altering such equilibrium partial pressure.

A gas-equilibrated, volatile-in-water detector comprises a gas-sensing chamber having an orifice closed by a hydrophobic, vapour-porous membrane, typically PTFE, sealed to the periphery of the orifice. Membrane is also sealed to an external wall of a surrounding enclosure and forms an entry point to a second gaseous enclosure external of the gas-sensing chamber. A PID or similar sensor generates a measurable current or voltage in response to the partial pressure of the analyte within the gas-sensing chamber without the sensor significantly altering such equilibrium partial pressure.

A detector for, and a method of, detecting analytes in gases in described. The detector comprises a sorbent for sorbing therein and/or thereon and/or desorbing therefrom, an analyte included in a gas exposed thereto, at a zeroth temperature, pressure (T.sub.0,P.sub.0), a controller arranged to change the zeroth temperature, pressure (T.sub.0,P.sub.0) to a first temperature, pressure (T.sub.1,P.sub.1) according to a first equation, to desorb and/or sorb at least some of the analyte; and a sensor arranged to sense at least some of the analyte and to output a response corresponding to the sensed analyte. The response comprises and/or is a characteristic response of the analyte. The first response is modified based on a first baseline response at the zeroth temperature, pressure (T.sub.0,P.sub.0).

An electrode stack assembly includes an electrically insulative substrate having a cavity therethrough extending, a first counter electrode on a top surface thereof and extending through the substrate, a second sensing electrode on a bottom surface thereof and extending through the substrate, and a third electrode having a top body portion on a top of the substrate, a bottom body portion on a bottom of the substrate, and a coupling pin passing through the substrate and electrically coupling the top and bottom body portions. The third electrode electrically separates the pin of the sensing electrode from the counter electrode.

An electrode stack assembly includes an electrically insulative substrate having a cavity therethrough extending, a first counter electrode on a top surface thereof and extending through the substrate, a second sensing electrode on a bottom surface thereof and extending through the substrate, and a third electrode having a top body portion on a top of the substrate, a bottom body portion on a bottom of the substrate, and a coupling pin passing through the substrate and electrically coupling the top and bottom body portions. The third electrode electrically separates the pin of the sensing electrode from the counter electrode.

An ion generation apparatus according to the present invention includes an electron emission device, an opposite electrode, and a controller, the electron emission device includes a lower electrode, a surface electrode, and an intermediate layer provided between the lower electrode and the surface electrode, the opposite electrode is provided to be opposite to the surface electrode, and the controller is provided to apply a voltage to the surface electrode, the lower electrode, or the opposite electrode such that a potential of the surface electrode becomes higher than a potential of the lower electrode and a potential of the opposite electrode in a positive ion mode.