146 results about "Reference cavity" patented technology

A method and device for measuring the amount of gas adsorbed by powder features that a prssure difference sensor is used to directly measure the pressure difference between gas supplying cavity and reference cavity whose gas amount is constant, and the algorithm for calculating the adsorbed amount is based on the pressure variations of specimen pool and gas supplying cavity or reference cavity. Its advantage is high correctness, precision and resolution.

Methods of bulk manufacturing high temperature sensor sub-assembly packages are disclosed and claimed. Sensors are sandwiched between a top cover and a bottom cover so as to enable the peripheries of the top covers, sensors and bottom covers to be sealed and bound securely together are disclosed and claimed. Sensors are placed on the bottom covers leaving the periphery of the bottom cover exposed. Likewise, top covers are placed on the sensors leaving the periphery of the sensor exposed. Individual sensor sub-assemblies are inserted into final packaging elements which are also disclosed and claimed. Methods of directly attaching wires or pins to contact pads on the sensors are disclosed and claimed. Sensors, such as pressure sensors and accelerometers, and headers made out of silicon carbide and aluminum nitride are disclosed and claimed. Reference cavities are formed in some embodiments disclosed and claimed herein where top covers are not employed.

The invention provides a fiber bragg grating combined optical fiber laser gas detection system with reference cavity compensation. The fiber bragg grating combined optical fiber laser gas detection system comprises an optical fiber laser, an optical isolator, a coupler, a second wavelength division multiplexer, a third wavelength division multiplexer, a first photoelectric detector, a second photoelectric detector, a third photoelectric detector, a fourth photoelectric detector, and a feedback control unit which are sequentially connected, wherein the optical fiber laser comprises a laser diode pumping source, a first wavelength division multiplexer, an active optical fiber, a first fiber bragg grating and a second fiber bragg grating and respectively emits a first wavelength laser beam and a second wavelength laser beam, the coupler is used for carrying out power beam splitting on light beams, the light beams subjected to the beam splitting are respectively introduced into a reference air chamber and a detection air chamber, the second wavelength division multiplexer is connected with the reference air chamber, the third wavelength division multiplexer is connected with the detection air chamber, the first photoelectric detector and the second photoelectric detector are connected to the second wavelength division multiplexer, the third photoelectric detector and the fourth photoelectric detector are connected to the third wavelength multiplexer to generate a first optical intensity signal, a second optical intensity signal, a third optical intensity signal and a fourth optical intensity signal; the feedback control unit receives the first optical intensity signal, the second optical intensity signal, the third optical intensity signal and the fourth optical intensity signal and uses a comparing result as a feedback signal for regulating the optical fiber laser.

A pressure sensor is described with sensing elements electrically and physically isolated from a pressurized medium. An absolute pressure sensor has a reference cavity, which can be at a vacuum or zero pressure, enclosing the sensing elements. The reference cavity is formed by bonding a recessed cap wafer with a gauge wafer having a micromachined diaphragm. Sensing elements are disposed on a first side of the diaphragm. The pressurized medium accesses a second side of the diaphragm opposite to the first side where the sensing elements are disposed. A spacer'wafer may be used for structural support and stress relief of the gauge wafer. In one embodiment, vertical through-wafer conductive vias are used to bring out electrical connections from the sensing elements to outside the reference cavity. In an alternative embodiment, peripheral bond pads on the gauge wafer are used to bring out electrical connections from the sensing elements to outside the reference cavity. In various embodiments, a regular silicon-on-insulator wafer or a double silicon-on-insulator wafer may be used as the gauge wafer, and appropriate micromachining steps are adopted to define the diaphragm. A layer of corrosion resistant material is deposited on the surface of the diaphragm that is accessed by the pressurized medium.