Abstract: A stack (10) of fuel cells (11) is to be tested for tightness of the fuel cell membranes. For this purpose, a tracer gas is introduced into the fuel feed channel (15) of the stack (10). The fuel discharge channel (16) is either open or it is closed. A carrier gas is fed to the feed air channel. (17) and led through the exhaust air channel (18) to a gas sensor (28) where a determination is made whether the carrier gas contains amounts of tracer gas. A defective fuel cell (11) can be located by introducing a lance comprising a sniffing probe into the corresponding channel (18) and determining the position of the probe.

Abstract: A test subject, which is filled with test gas, is placed in a testing chamber, which can be evacuated. A carrier gas is conducted into the testing chamber, so that a gas mixture made of carrier gas and test gas forms therein. The gas mixture is suctioned out of the testing chamber by a compressor pump. A testing gas sensor is connected to the outlet of the compressor pump. The test gas is contained in the compressed gas mixture at a partial pressure which is increased by the compression ratio. In this manner, the sensitivity of the test gas recognition is increased and/or the time constant of the measurement is shortened.

Abstract: The helium sensor comprises a housing that encloses a detection chamber. A side of the housing is closed by a permeable wall that is selective for helium. In the detection chamber, there is located an ion getter pump comprising an anode, a cathode and a magnetic field. The cathode, or a cathode leg is made of beryllium. Beryllium has a low atomic mass, whereby the likewise light-weight helium ions can be better incorporated into the cathode material.

Abstract: A gas probe for sampling gas molecules from a fluid. A housing includes an orifice and is adapted to be arranged in gas communication with a test gas sensor. The probe includes a stack of layers, whereby gas sample molecules have to pass through all layers of the stack in order reach the sensor. The stack includes at least a first membrane layer, a first spacer layer, a first filter layer and a second spacer layer. The housing includes an inlet for introducing blocking gas molecules into the second spacer layer and an outlet for discharging blocking gas molecules out of the first spacer layer. The gas probe is connectable to a control unit for controlling the blocking gas flow into the second spacer layer.

Abstract: A gas pressure measuring cell configuration has a thermal conduction vacuum cell according to Pirani (Pi), with a measuring chamber housing enclosing a measuring chamber and with a measuring connection which channels the gas pressure P to be measured into the measuring chamber. The measuring chamber has a heatable measuring filament connected to an electronic measuring circuitry. The electronic measuring circuitry is in thermal contact on one side of an insulating carrier plate and the carrier plate forms on the opposite side a component of the measuring chamber housing, wherein the measuring filament in series with a measuring resistor (Rm) is supplied directly by the electronic measuring circuitry in feedback and wherein the electronic measuring circuitry directly determines the resistance of the measuring filament.

Abstract: A hydrogen sensor includes a housing, which is closed off by a membrane that is made of palladium and selectively only pervious to hydrogen. The housing is evacuated and contains a Pirani pressure sensor. The membrane and the Pirani pressure sensor are each attached to a carrier. Both carriers are joined directly next to one another or kept at a distance by a connection piece. The hydrogen sensor has a high sensitivity and a low response time due to the relatively large membrane surface and the low housing volume. It can be produced in a small size and integrated in the handle of a sniffer-type leak indicator.

Abstract: The refrigeration compressor is a double-acting refrigeration compressor, comprising a piston which is freely guided on two cylinder sections that are opposite each other and that cannot be moved relative to each other, and which has a flow channel that extends internally through the piston, wherein each cylinder section and the piston have at least one check valve along the flow channel, wherein the check valves are arranged in such a way that the flow directions thereof are oriented in the same direction.

Abstract: The sniffing leak detector comprises a sniffing probe, a suction device and gas detector. An operator-activated switch initiates the beginning of a measuring operation. The switch starts a time measurement, wherein an alarm signal is generated by a signal transmitter at the end of a predetermined measuring period. The sniffing leak detector allows for an operator guidance from measuring point (MP) to measuring point, wherein the measuring period is predetermined and an adherence to the measuring period is monitored.

Abstract: A sniffing leak detector comprises a handle with a sniffing tip. Located at the sniffing tip is a measurement gas suction opening and a reference gas suction opening. The reference gas suction opening is intended for suctioning ambient gas. The reference gas suction opening is aligned substantially the same as the measurement gas suction opening such that both suction openings are sensitive in the same direction.

Abstract: The invention relates to a leak detector comprising a first sensor for detecting a gas component (helium) in a gas taken in. Because the sensor is susceptible to saturation or contamination, a second sensor is provided. The sensor is a thermal conductivity sensor. The thermal conductivity sensor has a lower detection sensitivity, yet, at a high concentration of the gas component, it does not risk being contaminated. The two sensors together allow for a large detection range, from extremely sensitive measurements to instances with high concentrations of the gas components as those which can occur with gross leaks.

Abstract: The leak detection appliance has a test inlet to which a test chamber containing the test specimen can be connected. A high-vacuum pump produces a high vacuum in a test gas detector. A preliminary vacuum pump contains two pump stages. In order to evacuate the test chamber, the pump stages are operated in parallel mode, with their suction capabilities being added. When the necessary vacuum has been achieved, the pump stages are operated in series in order to produce the necessary high vacuum—which is required for high detection sensitivity—on the test gas detector.

Abstract: In order to test water-bearing components for leak tightness, a coating (19) is provided, which comprises a mixture made of a water-soluble base substance and a generator substance. Upon contact with water, the coating (19) releases an indicator gas. The indicator gas is detected by a sensor (13).

Abstract: The present invention relates to gas sensor housing (1), comprising: a gas sensor (3) held by a housing body (11) below a primary gas permeable membrane (2); at least one connector element (10) moulded into the housing body (11) such that the respective ends thereof enable connectivity to the gas sensor (3) such that signals may be carried from the gas sensor (3) to the connector element (10); a sensor envelope (9) providing an enclosure for the housing body (11); means for retaining the primary gas permeable membrane (2) in place above the gas sensor (3); a spacer section (7) providing a separation distance (X) between the gas sensor (3) and the primary gas permeable membrane (2).

Abstract: A sound velocity sensor is defined by a hermetic multi-chambered enclosure for containing flowing gases and mixtures of gases. The contained flowing gases are acoustically excited and the acoustic energy is measured over a fixed distance between a first sending end of the enclosure and a receiving end. The speed of sound of the gases are determined by comparing the energy transmitted through the flowing gases at various frequencies so as to precisely determine the resonant frequency of the gases flowing through the enclosure. In accordance with the present design, the chambers of the enclosure include internal transition shapes therebetween for optimizing the transmission of acoustic energy through the flowing gases and also enhancing one or more additional resonant modes at higher useful frequencies. The transition shapes used in connection with the sensor can be at least one of parabolic, hyperbolic, linear and exponential in nature.

Abstract: A method for accurately calculating the thickness of deposited thin film layers onto a piezoelectric crystal blank in which dissimilar materials can be utilized, enabling determinations for various applications employing exotic materials. Additionally, the specific acoustic impedance (or equivalent z-ratio) of an unknown deposited material can be determined. The exact analytical solution nearly eliminates thickness errors when several layers of different materials are sequentially deposited on the same monitor quartz crystal.

Abstract: A membrane selectively permeable to light gases comprises a membrane body formed by a first plate and a second plate. The second plate comprises a thin layer that is selectively gas-permeable. In the region of windows, this layer is exposed. There, support is provided by a porous bottom wall in the first plate or by narrow bores in the second plate. A heating device causes a radiation heating of the windows.

Abstract: Calibrating a measuring cell arrangement having a diaphragm vacuum measuring cell having a programmable heater for heating the diaphragm vacuum measuring cell to a constant presettable temperature. The heater encompasses the measuring cells and is encompassed by an insulation jacket. The method includes setting a first heating temperature on the measuring cell to a constant preset value, performing a first calibration step by generating at least one preset pressure in a vacuum volume and obtaining vacuum measuring signals of the measuring cell and at least one reference measuring cell, storing pressure values in the memory, determining compensation values from the difference values of the measuring cell and the reference measuring cell, intermediately storing these difference values in a calibration data memory and gauging the measuring cell by transmitting the determined compensation values to the measuring cell data memory.

Abstract: An illumination device is provided at the handle-piece of a sniffing probe, in which the illumination device illuminates the region to be inspected. This incorporation considerably facilitates handling of the sniffing probe in difficult-to-access and poorly illuminated regions, for sniffing probes used for detecting gases, for example, for detecting a gas leakage in a cooling device of a motor vehicle.

Abstract: A cathode configuration for emission of electrons has a reaction zone connected to an entrance opening for the supply of neutral particles. The opening communicates with the cathode configuration for the ionization of the neutral particles and an ion extraction system communicates with the reaction zone. Ions from the extraction system are sent to a detection system and a mechanism for the evacuation of the mass spectrometer arrangement. The cathode configuration includes a field emission cathode with an emitter surface, wherein at a short distance from this emitter surface, an extraction grid is disposed for the extraction of electrons, which grid substantially covers the emitter surface. The emitter surface encompasses herein at least partially a hollow volume such that a tubular structure is formed.

Abstract: A membrane selectively permeable to light gases comprises a membrane body formed by a first plate and a second plate. The second plate comprises a thin layer that is selectively gas-permeable. In the region of windows, this layer is exposed. There, support is provided by a porous bottom wall in the first plate or by narrow bores in the second plate. A heating device causes a radiation heating of the windows.