Sensors and Actuators最新文献

The piezoelectric and pyroelectric properties of oriented films possessing dipole moments are increasingly being used in pressure, acoustic, thermal and optical devices. The performance of these devices in many applications may be enhanced by thin-film technology.The developing Langmuir-Blodgett thin-film deposition technique offers the opportunity to obtain highly oriented and uniform organic-based films in the 10–5000 nm thickness range. Special techniques must be used, however, to assemble these molecules in such a way as to result in polar multilayer films. Several possible deposition techniques are investigated, with one resulting in a polar and pyroelectric film about 50 nm thick.

A sensor system to detect and locate a tag for an automatic transport vehicle, e.g., a forklifter, is described. It consists of a laser scanner that scans a tag.

Due to an individual coding of each tag, a typical pulse train can be derived from the reflected light. This pulse train contains information about the tag identity and the tag position relative to the scanner. Data processing is done by a microcomputer within the scanner system, which transfers the data to the control system of the forklifter. Thus, the basis is given for a real-time computation of an optimized driving strategy.

An additional laser scanner detects even extremely faintly reflecting obstacles in a well-defined range in front of the vehicle and prevents collisions with persons and objects in the working area of the forklifter.

The application of four different conducting polymers (polypyrrole, poly-N-methylpyrrole, poly-5-carboxyindole and polyaniline) as sensors for organic vapours has been investigated.

The sensors are formed by the electrochemical polymerization of the appropriate monomers across a 12 μm gap between two gold microband electrodes. Upon exposure to vapours the polymers show conductivity changes that are rapid and in general reversible at room temperature.

Of the four polymers investigated, under the deposition conditions employed and for the vapours used (methanol, ethanol, acetone, ether and toluene), poly-5-caboxyindole is found to give the most stable, reproducible behaviour and to be the most promising material for sensor applications. The use of these materials in intelligent gas sensors is discussed.

SnO_2—x thin films with added platinum are studied. The SnO_2—x thin films are prepared by reactive electron beam evaporation of sintered pellets of SnO₂ powder. The deposited films are dipped into an aqueous solution of H₂PtCl₆·6H₂O and heat treated. The surface structure and composition of the prepared films are investigated by electron spectroscopy for chemical analysis, Auger electron spectroscopy and X-ray diffractometry. The electrical properties of the thin films and the effect of Pt addition on the gas-sensing characteristics have also been investigated.

The applied potential of amorphous silicon as a strain gauge material has been investigated. Measurements of the gauge factor, K, were carried out on a-Si/a-SiN_x thin-film structures deposited from a glow discharge plasma on polished stainless steel substrates. The conductance changes of phosphorus-doped a-Si under uniaxial strain lead to room temperature K values between −20 and −40, depending on the potential applied to the substrate. The control of K by the field effect makes it possible in principle to compensate for the temperature coefficients of the gauge factor.

The performance of a magnetic field sensor is described. The device is an improvement of an earlier magnometer reported by this group. It is based on the measurement of the elongation of a metallic glass ribbon (which has been annealed to give a high magnetomechanical coupling) by a tunneling tip. It operates in air and at room temperature. The present device is capable of detecting a field as small as 60 μOe and has a ribbon response of 1.7μm Oe^-1 (at a bias field of 0.85 Oe), which produces a signal response of 30 V Oe^-1. Methods of further improving the sensitivity are discussed.

A theory of the decrease in the sensitivity and the Hall angle in silicon magnetic sensors is pre- sented. The mean collision-free time decreases in the presence of a strong electric field, which results in a smaller Hall angle. The total deflection of the charge carriers in a vertical dual-collector bipolar magnetotransistor is the sum of the contributions of the deflection in the collector-base depletion layer and the deflection in the ohmic collector region. The sensitivity of a magnetotransistor de- creases due to the decrease in the Hall angle in the depletion layer and the increased power dissipa- tion and temperature of the device. The sensitivity decreases by 25% when the collector-base voltage is increased by 10 V.