Manganin thin film sensor for force sensing

For the measurement of force inside inaccessible mechanical parts, a thin film sensor is necessary. Piezoresistive sensors are capable of converting mechanical parameters such as force or pressure into electrical parameters. The alloy manganin is a suitable material for the active zone of a piezoresistive sensor. It has a small temperature coefficient and an adequate pressure coefficient. Also, manganin has been field-tested in conventional strain gauges up to 1500 N mm−2. Aluminium oxide has been used to create two insulating coatings. It has been shown that a sensor with three coatings (aluminium oxide–manganin–aluminium oxide) can be deposited on steel shafts. Physical vapour deposition (PVD) and photolithographic processes were used for plating and sensor structuring of the manganin layer. A multilayer Al–O film deposited by a PVD-process has made it possible to reduce the phenomenon of pinholes which causes short circuits between the steel shaft and the active sensor material manganin.