Showing papers on "Gauge factor published in 1992"

Polysilicon as a material for microsensor applications

Abstract: Important characteristics of boron-doped LPCVD polysilicon layers with regard to sensor applications are presented. Properties such as the resistivity, temperature coefficient of the resistance, gauge factor and long-term stability are described. A pressure sensor utilizing polysilicon piezoresistors with a measurement range of 1 bar and a sensitivity of roughly 11 mV/V FS, a laser-trimmed polysilicon temperature sensor with a sensitivity of −3.4 × 10 −3 K −1 and non-linearity of less than 0.5% and a pressure sensor with polysilicon-based on-chip calibration and temperature compensation are described.

Piezoresistivity in vapor-deposited diamond films

Abstract: We report the observation of a very large piezoresistive effect in both polycrystalline and homoepitaxial chemical‐vapor‐deposited diamond films. The gauge factor for polycrystalline p‐type diamond at 500 microstrains was found to be only 6 at room ambient, but increased rapidly with temperature, exceeding that of polycrystalline silicon (30) at 35 °C, and that of single‐crystal Si (120) at 50 °C. For strain and current flow in the [100] direction, the gauge factor of a (100)‐oriented homoepitaxial diamond film was found to be at least 550 at room temperature. Although the origins and unexpected temperature dependence of piezoresistive effect in diamond are not yet understood, these findings may suggest diamond‐based sensors with performance significantly superior to that of their Si counterparts.

Etched fibers as strain gauges

Abstract: A class of optical fiber intensity sensors that do not require the use of external structures to impose perturbations on fibers is presented. The topological structures are formed directly onto the fiber cladding. The geometry of the features is defined photolithographically and the structures are formed by chemical etching. The etched fiber sensing elements have been fabricated and tested as strain sensors. Depending on the amount of the cladding material removed and the symmetry of the etched structure, the measured gauge factor of the etched fiber strain sensors may be larger than 100. The responses of the optical fiber strain gauges are linear, repeatable, have a high cyclic endurance and no measurable hysteresis. These sensors can be used to monitor a strain as large as 0.4%. >

Laser-recrystallized polysilicon layers in sensors

Abstract: The process of laser recrystallization of polysilicon layers deposited on thermally oxidized silicon wafers and the structure of the obtained layers have been studied. The recrystallization is carried out by CW YAG laser radiation. The piezoresistive properties of n- and p-type poly-Si layers with different carrier concentrations have been investigated. The longitudinal gauge factor for p-type layers changed from 26 to 55 with a decrease of carrier concentration from 10 20 to 10 17 cm −3 . The temperature coefficients of resistivity and the gauge factor for the investigated layers have been determined. Miniature piezoresistive pressure and force sensors with polysilicon resistors have been constructed.

Applicability of discontinuous palladium films as strain gauges

Abstract: Discontinuous palladium films were prepared by evaporation and sublimation. The variation of the direct current resistance of the as-deposited films with time was investigated in air at room temperature. Films prepared by sublimation exhibited better stability as compared with that of films prepared by evaporation. The piezoresistance of the discontinuous palladium films was measured at different strains and the gauge factor, v, was deduced. It was found that v of films prepared by sublimation was higher than that of films prepared by evaporation. Palladium films prepared by sublimation are thus good candidates as sensors for measuring extremely small strain.

Strain gauge measurement

Abstract: Strain gauge model testing is commonly applied in mechanical and civil engineering to complement analytical, numerical and finite element models and to assess the relative behaviour of components. In biomechanics comparative investigation of product performance in vitro is often obtained by testing models fitted with different prostheses in a commercial testing machine. Appropriate measures need to be taken to ensure that the data obtained from such tests represents a comparison of the products in vitro, as opposed to bias inadvertently introduced into the test by the techniques and procedures used by the experimenter.

Calibration systems for strain gauges to be used at cryogenic temperatures

Abstract: The dependence of apparent strain (AS) on temperature down to 4.2 K has been studied for different types of strain gauges applied on several materials (AISI 316 LN, Cu, Al). The determination of the gauge factor and its variation with temperature made it necessary to develop calibration systems designed to ensure adequate measurement reproducibility for a comparison between results obtained in different laboratories.

Piezoresistivity of Polycrystalline Diamond Films

Abstract: Polycrystalline diamond film (PDF) is known for its high power, high temperature, and radiation hard potential. The interest in piezoresistivity of PDF is that it is a candidate for high temperature sensing (e.g., pressure sensor). Piezoresistivity measurements were taken of boron-doped PDF grown by microwave-plasma chemical vapor deposition(CVD). Three substrates, silicon, aluminum nitride and tungsten were used. Films were detached from these substrates, then attached to a ceramic substrate. The piezoresistivity varies, dependent on the original host substrate. For example, at room temperature, the PDF film from tungsten has a greater gauge factor, around 75. The carrier activation energy of this film, determined from log R(1/T), was nominally 0.25eV. Combining thick film technology and CVD processes, patterned B-doped PDF has been achieved monolithically on AIN substrates. The characteristics of this configuration is being investigated and will be presented.

Properties of discontinuous gold thin films deposited on a silicon substrate

Abstract: Experimental results on the dependence on deposition conditions of the electrical resistance and gauge factor of discontinuous gold films in the vicinity of the percolation threshold are reported. The three-dimensional nature of the films is emphasized. The gauge factor reveals anomalous behaviour.

Metallic thin film resistor strain gauge

Abstract: PURPOSE:To improve the stability and to obtain a highly reliable metallic thin film resistor strain gauge by using a thin film of Fe-Cr-Co-W alloy having a high melting point as a resistance body of the metallic thin film resistor strain gauge CONSTITUTION:An alumina substrate is used for a substrate 1 and, Fe-Cr-Co-W (Cr 3-35%, Co not more than 40%, W not more than 9% and Fe the remaining in weight ratio) is used as an ingot 3 A bell jar 4 as a deposition apparatus is vacuumized to 3X10 torr thereinside The ingot 3 is heated for vacuum deposition As a result, a thin film of Fe-Cr-Co-W, approximately 1mum thick, is formed on the alumina substrate 1 Then, an Ni layer 7 and an Au layer 8 as metallic electrodes are formed on both sides of the substrate with the thin film Accordingly, a metallic thin film resistor strain gauge with a high gauge factor can be obtained The gauge is highly reliable and indicates a high value