Kristal Instrumente Ag

Kistler Instrumente Ag

Kistler Instruments Ag

Kristal Instruments Ag

Hans-Conrad Sonderegger

Reto Calderara

Peter Wolfer

Hans-Ulrich Baumgartner

Alfred Wenger

Paul Engeler

Peter Weber

Max Vollenweider

Rene Tanner

Eugen Lutz

Reto Calderra

Hans-Rudolf Derrer

A multi-component dynamometer for measuring forces and torques includes two force introduction plates and pre-oriented transducer elements without housing arranged between them. Each transucer element comprises typically a rectangular plate and two pre-oriented piezoelectric elements fixed thereon, one of these being sensitive to shear in a direction parallel to one edge of the carrier plate and the other being sensitive to pressure in a direction parallel to the normal of the carrier plate. The pre-oriented transducer elements enable the number of piezoelectric elements and electrical connections to be reduced substantially when assembling measuring platforms, as well as the amount of orientation and testing work. The platforms can be made flatter and more rigid, thereby raising the natural frequency. The electronic measuring and evaluation parts can be integrated partially or wholly into the dynamometer.

Multi-component dynamometers

A piezoresistive force-measuring element comprises at least two force-introduction plates with an electrical conductor subjected to plastic deformation arranged between them. The force-introduction plates transmit the forces acting on them without mechanical shunting onto the conductor between them. The change of electrical resistance caused by the force sustained can be used to measure force, accompanied by plastic as well as elastic deformation of the conductor. The typically annular or rectangular force-introduction plates can be fitted inside a housing which may include a bridge circuit for determining the resistance change as well as other electronics enabling the device to be used as a transmitter. By placing the conductor in grooves or anchoring it in the pores of the adjacent plates, an essentially hydrostatic loading of the conductor is obtained, bringing an enormous extension of the measuring range while the measuring accuracy is enhanced owing to the reduced hysteresis. The sensitivity and the measuring range can be adjusted by appropriate prior deformation of the conductor. Permanent deformation of the conductor resulting from high loads makes possible subsequent determination of the magnitude of the peak forces acting on the measuring element.

Piezoresistive force-measuring element and its use for determining

A transducer, particularly for ballistic high pressure measurements, comprises an assembly body, with a shoulder sealing section and a sensor member, which can be received in a recess in the assembly body. The assembly body can be screwed into a component, e.g. a gun barrel, the measurement area on the sealing section being sealed. The assembly body has a tubular extension extending beyond the sealing section, which extension encompasses the sensor member on a cylindrical fitting face. The high sealing forces required for sealing the measurement area are kept remote from the sensor member. The measuring sensitivity of the transducer is therefore independent of the prevailing tightening torques. A cylindrical gap between the sensor member and assembly body provides additional insulation between the sealing forces and the prestress forces prevailing in the sensor member. The cylindrical gap is sealed against the pressure medium by a force fit or weld between the assembly body and the sensor member. A reception space can be provided ahead of the diaphragm section of the sensor member, which reception space can be formed by an annular section projecting from the diaphragm section, and can be provided with replaceable thermal and erosion protection devices.

High pressure transducer

The invention relates to a force transducer with at least 100 pC/N sensitivity. The piezo elements of this force transducer are connected rigidly to the force introducing elements, and therefore require no mechanical prestressing. A diaphragm may be provided and is then the only force shunt with a maximum proportion of 5%. The main force flow runs in these transducers through the piezo elements themselves, thereby keeping the pseudo-pyro effect, which is frequently brought about by mechanical shunting, within very narrow limits. Because of bottlenecks in the heat guide path to the piezo elements and the symmetrical construction of the supports, heat transients are also prevented from exerting an appreciable effect on the position of the zero point. This provides zero point stability, which allows accurate measurements in the 0 . . . 1 N range, even where the ambient conditions are unfavorable from the point of view of temperature.

Piezoelectric transducer for low forces

A transducer insert for installing in sensors for measuring mechanical variables includes a semi-conductor body with a measuring diaphragm part of which has diffused-in strain-sensitive resistance paths or capacitor electrodes and also connecting contacts on one side. The semi-conductor body is connected to a base body of insulating material, preferably by an anodic method, through which electrically conductively coated channels pass. The channels open at a recess in the base body which is bridged by the measuring diaphragm part. The electrically conductive layers of the channels extend along the recess to the vicinity of the connecting contacts of the semi-conductor body and are directly connected thereto in an electrically conductive manner by the so-called corner drop method, e.g. by glueing, soldering or thermo-compression. A central projection can be provided in the recess of the base body which creates a deflection limit for the measuring diaphragm part. The transducer insert can be manufactured according to the so-called batch method.

Transducer inserts; methods of making them and sensors for measuring

A piezoresistive transduction element for incorporation into a pressure transducer includes a plate defining a diaphragm zone and preferably of silicon with piezoresistances diffused into it, an insulating plate of a glass material and a base plate. The plates are preferably connected to each other by anodic connections in a series of steps. The base plate is made of a material having substantially the same coefficient of thermal expansion as that of the material of the plate which defines the diaphragm zone. Furthermore, the dimensions of the base plate are matched to those of the diaphragm plate. By these measures the deformation forces exerted by the base plate and diaphragm plate on the insulating plate upon changes in temperature are of substantially the same magnitude and therefore there is minimum bending of the diaphragm plate. A symmetrical transduction element is created which has minimum zero point displacement and minimum sensitivity changes in use. Pressure transducers equipped with such piezoresistive transduction elements are therefore appropriate for high measuring accuracy, particularly in combination with an improved, elastically extensible securement of a holder which carries the transduction element within the transducer housing.

Pressure transducer utilizing a transduction element

A high pressure transducer, especially for ballistic pressure measurements, with a body member and a sensor part, the body member can be screwed into a threaded mounting bore provided in a structural component, whereby the body member comes into sealing contact with its sealing surface against a seating surface of the mounting aperture. The body member is provided with a recess, into which projects an extension on the sensor part to be secured along its end-face on the body member. An annular gap is provided between the extension of the sensor part and the recess in the body member, which causes the force flux lines produced by the sealing forces not to pass through the sensor part so that the latter remains unaffected by changing conditions of the force flux lines, i.e. by the prevailing tightening torques.

A piezoelectric strain/force transducer is described, which is attached preferably by only one locking screw to a test specimen or machine part. The force transmitting member of the transducer comprises two bearing surfaces at a distance apart, which bear frictionally on the surface of the machine part and experience a change in spacing in the case of a change in length of the machine part. Due to this, a resilient member, which can be adapted to a desired sensitivity of the gauge, is tensioned and a set of piezoelectric plates held under precompression in the force-transmitting member are subjected to a corresponding shearing force. The piezoelectric plates are cut or polarized so that they respond piezoelectrically solely to shearing forces. The resulting piezoelectric charge is a measurement of the strain or mechanical stress of the machine part and can be used for monitoring or controlling machines or components, in particular those which are subjected to cyclic loads.

Growing community of inventors

Neftenbach, Switzerland

Hans-Conrad Sonderegger