Measuring device including detection of deformations
A measuring device is described which has a metal body deformable in accordance with a value to be measured. A sensor element having a metal carrier and ohmic resistors formed thereon in metal thin-film technique is connected to the metal body by welding and generates a signal adapted to be electrically evaluated which corresponds to the deformation of the metal body. The weld for connecting the metal body and the sensor element completely encloses the metal carrier at its circumference. The metal body has, at the welded connection with the metal carrier, a material thickness t which is completely penetrated by the weld. The value to be measured by the measuring device comprises force, pressure, temperature, torque or combinations thereof.
1. A force measuring device comprising:
a metal body deformable in accordance with a value to be measured, a sensor element having a metal carrier and ohmic resistors formed thereon in metal thin-film technique, the sensor element being connected to the metal body by welding and generating a signal adapted to be electrically evaluated corresponding to the deformation of the metal body, wherein the metal carrier is neutrally clamped by the metal body through a uniformly solidified liquid zone formed during welding between the metal carrier and the metal body across the material thickness t of the metal body, and
at the welded connection with the metal carrier, the material thickness t of the metal joint and the metal carrier, and the welded joint completely encloses the metal carrier at its circumference.
2. The measuring device according to claim 1 , wherein the value to be measured is associated with a force or torque or combinations thereof.
3. The measuring device according to claim 1 , wherein the material thickness t is within the range of from 0.2 to 1.2 mm.
4. The measuring device according to claim 1 , wherein, at its circumference, the metal carrier is provided with a flange the material thickness of which is substantially equal to t, the welded joint being a butt joint.
5. The measuring device according to claim 4 , wherein the metal carrier is cup-shaped and the flange is axially confined by a circumferential groove introduced into the cup wall.
6. The measuring device according to claim 1 , wherein the metal carrier of the sensor element has an outer diameter of 5 to 15 mm.
7. The measuring device according to claim 1 , wherein the resistors of the sensor element are wired with each other for forming at least one Wheatstone full bridge and supply a signal which is proportional to the elongation of the sensor element.
8. The measuring device according to claim 7 , wherein each Wheatstone bridge is provided with four or five electric connecting surfaces on the sensor element for connecting an evaluating unit.
9. The measuring device according to claim 7 , wherein at least two resistors of a Wheatstone bridge are formed by two resistors switched in series between each of which an electric connection is provided to which a variable resistor K can be applied in order to specifically unbalance the Wheatstone bridge.
10. The measuring device according to claim 9 , wherein the signal of the unbalanced bridge is supplied to the evaluating unit which is designed to check itself by way of this signal.
11. The measuring device according to claim 1 , wherein the resistors of the sensor element are wired with each other for forming at least two Wheatstone full bridges and supply a signal which is proportional to the elongation of the sensor element.
12. The measuring device according to claim 1 , wherein the resistors of each bridge are arranged in pairs, respectively, at right angles with respect to each other on the sensor element and, if more than one bridge is provided, the individual bridges are arranged so as to be differently aligned relative to each other.
13. The measuring device according to claim 12 , wherein two bridges are provided which are arranged to be offset by 90° relative to each other.
14. The measuring device according to claim 12 , wherein two bridges are provided which are arranged to be offset by 45° relative to each other.
15. The measuring device according to claim 12 , wherein two bridges are provided which are arranged to be offset by 90° relative to each other and a further bridge is provided which is arranged to be offset by 45° vis-à-vis the two bridges arranged perpendicularly to each other.
16. The measuring device according to claim 12 , wherein two pairs of bridges are provided which include bridges arranged to be offset by 90° relative to each other, wherein the two pairs of bridges are arranged to be offset by 45° relative to each other.