Abstract: A closed path infrared sensor includes an enclosure, a first energy source within the enclosure, at least a second energy source within the enclosure, at least one detector system within the enclosure and a mirror system external to the enclosure and spaced from the enclosure. The mirror system reflects energy from the first energy source to the at least one detector system via a first analytical path and reflects energy from the second energy source to the at least one detector system via a second analytical path. Each of the first analytical path and the second analytical path are less than two feet in length.

Abstract: A closed path infrared sensor includes an enclosure, a first energy source within the enclosure, at least a second energy source within the enclosure, at least one detector system within the enclosure and a mirror system external to the enclosure and spaced from the enclosure. The mirror system reflects energy from the first energy source to the at least one detector system via a first analytical path and reflects energy from the second energy source to the at least one detector system via a second analytical path. Each of the first analytical path and the second analytical path are less than two feet in length.

Abstract: A closed path infrared sensor includes an enclosure, a first energy source within the enclosure, at least a second energy source within the enclosure, at least one detector system within the enclosure and a mirror system external to the enclosure and spaced from the enclosure. The mirror system reflects energy from the first energy source to the at least one detector system via a first analytical path and reflects energy from the second energy source to the at least one detector system via a second analytical path. Each of the first analytical path and the second analytical path are less than two feet in length.

Abstract: A closed path infrared sensor includes an enclosure, a first energy source within the enclosure, at least a second energy source within the enclosure, at least one detector system within the enclosure and a mirror system external to the enclosure and spaced from the enclosure. The mirror system reflects energy from the first energy source to the at least one detector system via a first analytical path and reflects energy from the second energy source to the at least one detector system via a second analytical path. Each of the first analytical path and the second analytical path are less than two feet in length.

Abstract: A photoacoustic sensor includes a sensor system for photoacoustic detection, at least one noise canceling pressure sensor and a control system in operative connection with the noise canceling pressure sensor to actively cancel the effects of noise in the environment on the sensor system. Another photoacoustic sensor includes a measurement volume, a source of light energy, a photoacoustic pressure sensor, and at least one vibration canceling sensor (for example, a microphone or an accelerometer). A further photoacoustic sensor includes a measurement volume, a source of light energy and a photoacoustic pressure sensor. The measurement volume has an inner surface that is continuously curved over substantially the entire inner surface other than where a window in optical connection with the source of light intersects the measurement volume.

Abstract: A gas sensor includes a light source, a power source in operative connection with the light source and a control system in operative connection with the light source and the power supply. The control system is adapted to control power input from the power source to the light source such that the time period of the control frequency is shorter than the thermal time constant of at least one of (i) the infrared light source, (ii) the gas within the sensor, or (iii) a detector of the sensor. The time period of the control frequency can, for example, be no greater than ? of the thermal time constant, no greater than 1/10 of the thermal time constant, or even no greater than 1/20 of the thermal time constant. A feedback signal can be provided to the control system assist in achieving control.

Abstract: A gas sensor includes a light source, a power source in operative connection with the light source and a control system in operative connection with the light source and the power supply. The control system is adapted to control power input from the power source to the light source such that the time period of the control frequency is shorter than the thermal time constant of at least one of (i) the infrared light source, (ii) the gas within the sensor, or (iii) a detector of the sensor. The time period of the control frequency can, for example, be no greater than ? of the thermal time constant, no greater than 1/10 of the thermal time constant, or even no greater than 1/20 of the thermal time constant. A feedback signal can be provided to the control system assist in achieving control.

Abstract: A photoacoustic sensor includes a sensor system for photoacoustic detection, at least one noise canceling pressure sensor and a control system in operative connection with the noise canceling pressure sensor to actively cancel the effects of noise in the environment on the sensor system. Another photoacoustic sensor includes a measurement volume, a source of light energy, a photoacoustic pressure sensor, and at least one vibration canceling sensor (for example, a microphone or an accelerometer). A further photoacoustic sensor includes a measurement volume, a source of light energy and a photoacoustic pressure sensor. The measurement volume has an inner surface that is continuously curved over substantially the entire inner surface other than where a window in optical connection with the source of light intersects the measurement volume.

Abstract: The present invention relates to a photoacoustic gas sensor utilizing diffusion having a sensing volume and an acoustic pressure sensor volume containing an acoustic pressure sensor such that the fluid connection between the sensing volume and the acoustic pressure sensor volume restricts the flow of analyte gas therethrough but does not restrict the transmission of the photoacoustic signal therethrough.

Abstract: The present invention relates to an electronic circuit for measuring small amounts of charge or small electrical currents. One embodiment of the present invention provides an electronic circuit for measuring current or charge that can be used with a variety of sensing media (including high impedance sensing media) that produce a signal by either charge or current production or induction in response to physical phenomena occurring within the sensing media. In another embodiment, the voltage level (bias) of either the sensing or reference electrode can be switched relative to the other upon receipt of a triggering pulse. This changes the polarity of the electric field to cause charge of the opposite polarity to be driven to the sensing electrode, thereby eliminating the need to electrically connect a discharge path to the sensing electrode to clear the charge accumulated at the sensing electrode.

Abstract: The present invention relates to an electronic circuit and an array of such circuits for precisely measuring small amounts or small changes in the amount of charge, voltage, or electrical currents. One embodiment of the present invention provides an electronic circuit for measuring current or charge that can be used with a variety of sensing media (including high impedance sensing media) that produce a signal by either charge or current production or induction in response to physical phenomena occurring within the sensing media. In another embodiment, the voltage level (bias) of either the sensing or reference electrode can be switched relative to the other upon receipt of a triggering pulse. This changes the polarity of the electric field to cause charge of the opposite polarity to be driven to the sensing electrode, thereby eliminating the need to electrically connect a discharge path to the sensing electrode to clear the charge accumulated at the sensing electrode.

Abstract: Generally, the present invention provides a recirculating filtration system for use with a transportable ion mobility spectrometer in gas chromatography applications. The transportable recirculating filtration system comprises a pump and a set of filters and flow sensors connected to an ion mobility spectrometry sensor having a gas chromatograph column at its inlet. The IMS sensor's outlet flow is cleaned by the filters and recirculated by the pump back into the IMS sensor as the carrier fluid stream flow. A portion of the IMS sensor's outlet flow equal to the amount of flow introduced into the sensor as the sample is exhausted from the filtration system to maintain a constant total flow volume through the system as the sample is being analyzed. Preferably, the multicapillary column is sealed to a heated transfer line leading to the sample stream inlet of the IMS sensor. The transfer line is preferably maintained at a temperature 10.degree. C.-40.degree. C.