Abstract: The detector region of a gas analyzer is interfaced to a source of gas under analysis, such as the atmosphere, by means of an adsorber type preconcentrator, which preferentially adsorbs the gaseous constituent of interest, such as relatively heavy hydrocarbons, while permitting the other lighter hydrocarbons, water vapor, and permanent gases to pass thereby without appreciable adsorption. After a substantial volume of gas to be analyzed has passed through the adsorber stage, the adsorbed materials are desorbed from the surface of the adsorber into the input stage of a membrane separator. As a consequence, the partial pressure of the constituent of interest is greatly increased at the input stage of the membrane separator. The gaseous constituent of interest is then passed through the membrane separator, and further separated therein from water vapor, the permanent gases and some of the lighter hydrocarbons and then passed into the detector region of the gas analyzer.

Abstract: A capacitive force transducer, particularly suited for use as a microphone or as a phonograph needle pick-up cartridge, comprises a diaphragm electrode insulatively held to a lip portion of a recess in a second electrode, thereby forming a capacitive detector. The lip structure of the second electrode structure has a capacitive face region diverging from a virtual pivot region at the lip where the diaphragm is pivotably affixed to the recessed electrode. In this manner, the quiescent capacitance is defined predominantly by the capacitance near the lip, which is relatively small and defined and the change in capacitance for a given deflection of the diaphragm is relatively large, thereby improving the sensitivity of the transducer. In the case of a phonographic pick-up cartridge, the pick-up needle is coupled to the diaphragm so that vibrations induced in the needle produce corresponding vibrations of the diaphragm.

Abstract: In the thermal gas pressure gauge, a foil heater has a heater surface disposed in gas communication with the gas to be measured and the heater surface is thermally cycled at first and second reference frequencies to produce cyclical heating of the gaseous material adjacent the heating element. A directional microphone is disposed facing the heating element to derive signals of an amplitude determined by the amplitude of the cyclical heating effect of the gaseous material at the first and second reference frequencies. The detected signals are synchronously detected to produce a pair of dc outputs indicative of pressure in two respective pressure regimes. In an overlap pressure regime the two dc outputs are converted to digital signals which are correlated with pairs of values tabled in a read only memory for reading out a digital signal indicative of the pressure. In a low pressure regime from approximately 10.sup.

Abstract: The force transducer includes a composite spring structure having first and second folded cantilever leaf spring portions coupled to the region to receive the force to be measured. The first and second leaf spring portions extend outwardly from, and are angularly displaced with respect to each other, around an axis of sensitivity. Each folded cantilever leaf spring portion includes first and second generally parallel elongated leg portions extending outwardly from the axis of sensitivity with each of said leg portions being coupled together at the outer end by a coupling structure which is free to move both parallel to and perpendicular to the axis of sensitivity in response to displacement of the inner end of one of said leg portions relative to the other along the axis of sensitivity in response to application of the force to be measured to the inner ends of the leg portions.

Abstract: Solid state folded leaf spring force transducers are fabricated by batch photolithographic and etching techniques from a monocrystalline material, such as silicon. The folded leaf spring structure includes elongated gaps separating adjacent leaf spring leg portions, such elongated gaps being oriented parallel to a crystallographic axis of the monocrystalline material. In a preferred embodiment the monocrystalline material is of diamond cubic type and the leaf spring gaps extend in mutually orthogonal directions parallel to the <011> and <011> crystallographic axes, respectively. In a preferred method of fabricating the spring structure, the structure is etched from a monocrystalline wafer by means of an anisotropic etchant so as to more precisely define angles and dimensions of the resultant spring structure.

Abstract: An infrared laser absorption spectrometer is disclosed wherein a pair of detector cells are disposed serially along the laser beam path. The laser beam is modulated to produce a modulation of the absorption by the sample materials in the two cells. Modulated absorption by the samples produces an acoustic wave in each cell which is detected by a suitable microphone and subtracted so as to produce a difference signal corresponding to the difference in infrared absorption between the two cells so that undesired background effects common to both cells are cancelled. A pressure controller, which is responsive to the pressure difference between the sample pressure in the two cells at a frequency substantially below the beam modulation frequency is employed for controlling the pressure differential. In one embodiment the pressure controller includes a compliant membrane partitioning the two cells so that the membrane may move so as to equalize the pressures.