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: In laser absorption spectroscopy a fluid sample is irradiated with a beam of coherent optical radiation preferably in the infrared band. A detector such as an acoustic detector or thermal detector is coupled in acoustic or thermal energy exchanging relation, respectively, with the fluid medium to detect the absorption of energy, if any, by the fluid from the beam of coherent radiation. One or more of the physical or chemical parameters of the fluid or substances interacting with the fluid are changed and resultant changes, if any, are detected in the absorption of energy by the fluid to yield information concerning the fluid or substances interacting with the fluid.

Abstract: In an infrared laser absorption spectrometer, an infrared laser beam of predetermined wavelength, in the infrared absorption spectrum, is beamed into a liquid sample under analysis. Components of the liquid sample absorb energy from the infrared beam, as a function of the infrared wavelength of the beam, to produce heating of the liquid. A thermal detector is disposed in heat exchanging relation with the liquid sample for detecting the heating effect in the liquid due to absorption of the infrared radiation. This detection scheme is particularly useful for monitoring the effluent of a liquid chromatograph as it provides specific detection.

Abstract: Sample material of retention time peaks of a chromatograph are exposed to infrared radiation at first and second wavelengths and the absorption of the infrared energy by the sample peak is measured. The measured infrared absorption at the first and second wavelengths is correlated with the retention time of the sample peak as an identification of the sample material. In addition, overlapping retention time peaks are resolved by detecting the change in the ratio of the infrared absorption at the first and second wavelengths as a function of retention time for a given peak.

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.

Abstract: In an infrared laser optoacoustic spectrometer, the optoacoustic cell is acoustically isolated from a flowing stream to be analyzed, such as the output stream of a retention time chromatograph, by means of mufflers disposed upstream and downstream of the optoacoustic cell.