Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
  • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
  • G01L1/2268—Arrangements for correcting or for compensating unwanted effects
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
  • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
  • G01L1/225—Measuring circuits therefor
  • G01L1/2262—Measuring circuits therefor involving simple electrical bridges
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
  • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
  • G01L9/0051—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance
  • G01L9/0052—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of piezoresistive elements
  • G01L9/0055—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of piezoresistive elements bonded on a diaphragm
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
  • G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
  • G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges

Definitions

• the invention relates to a measuring device for measuring physical quantities, such as force, pressure, temperature,
• Measuring device are detected deformations of a membrane made of metal, in which the size to be measured in any way, by means of deformation-induced changes ohmic resistors.
• Resistors of a bridge in the region of the compression of the loaded membrane are arranged, while the other resistors are arranged in the region of the strain of the loaded membrane.
• Fig. 9 shows a conventional arrangement of a
• Measuring task and the structure of e.g. is specified as DMS.
• High-impedance resistors are expensive components if precision and durability are required.
• the present invention seeks to propose a measuring device that provides reliable high accuracy with simple means.
• the measuring device for measuring a physical quantity has at least one Wheatstone bridge in which at least one bridge resistor contains at least one deformation-sensitive ohmic measuring resistor which generates an electrically evaluable signal in accordance with a deformation.
• a Wheatstone bridge has two voltage dividers, each with two bridge resistors - four
• Bridge circuit are interconnected, wherein one of the two voltage divider connected to the middle tap line is referred to as a bridge branch.
• bridge resistance in this text and in the claims means such a resistance element of the
• the measuring device according to the invention also has a
• a detuning resistance is at least a resistor (a bridge resistor can be several
• Resistors included) in the Wheatstone 'see bridge medium or directly parallel optional switchable are included. According to the invention, a deformation-insensitive resistance is further provided, which with the
• Bridge resistance is connected in series.
• switchable Verstimmwiderstand can be low impedance, i. in the range of about 20 to 200 ohms. These components are long-term and temperature stable, inexpensive and available as a standard commercial components even with high accuracy.
• Measuring device against unwanted influences is less sensitive, e.g. Noise or dirt extending between the taps or contact points on surfaces of the
• At least two bridge resistors of a Wheatstone bridge are each formed by two series-connected resistors, between which an electrical connection is provided, to which the detuning resistor can be applied. In this way you can detune the zero point of the bridge voltage.
• the measuring device can have a plurality of deformation-sensitive ohmic measuring resistors, which are used to form
• At least two Wheatstone 'full bridges are interconnected, it being sufficient if at least one resistor of one of the bridges can be connected to the Verstimmwiderstand.
• the measuring device according to the invention may have a membrane corresponding to a size to be measured
• Membrane may include bending forces, tensile forces, compressive forces,
• the quantity to be measured can thus be a direct or indirect cause of the deformation of the membrane, so that there is a correlation between the deformation of the membrane and its cause (i.e., the quantity to be measured) and the conclusion about the size to be measured.
• the deformation-sensitive ohmic measuring resistors are preferably formed on the membrane in metal thin-film technology and change their value according to the deformation of the membrane.
• Such resistors, whose resistance changes with a deformation, are in the form of
• Resistors are due to the process very firmly with the
• Evaluation unit is provided.
• the evaluation unit is preferably designed such that it can check itself based on the signal of the detuned bridge.
• each bridge is arranged in pairs at right angles to each other and the individual bridges are arranged differently oriented relative to each other. If the bridges are arranged offset relative to each other by 90 °, mutually perpendicular deformations are basically directly detectable. If two bridges are provided which are offset relative to each other by 45 °
• more than two bridges can be provided, so for example.
• Two bridges can be arranged offset relative to each other by 90 ° aligned and another bridge is offset relative to the two mutually perpendicular bridges arranged offset by 45 °.
• Possible is also an arrangement of bridges, in which two pairs of bridges are provided, which have relative to each other offset by 90 ° aligned arranged bridges, wherein the two pairs of bridges are arranged offset relative to each other by 45 °. The detection of the deformations can thus be carried out accordingly.
• Fig. 1 is a sectional view of a first
• Fig. 2 is a sectional view of a second
• Fig. 3 is a usable with the invention
• FIG. 4 shows an external circuit of the bridge circuit from FIG. 3 that can be used with the invention
• Fig. 5 is a usable with the invention
• Fig. 6 shows another exemplary arrangement of two Wheatstone usable with the invention
• Fig. 7 still a usable with the invention
• Fig. 8 is a usable with the invention
• Fig. 1 shows a sensor element 10 in section, which is installed in a metal body 2.
• the sensor element 10 has a pot-shaped metal carrier 1 with a membrane and a recess E on its circumference, so that a flange portion 3 is formed, which is connected by means of a weld 4 with the metal body 2.
• the deformable metal body 2 has a substantially tab-like shape, which in this schematic
• the material thickness or sheet thickness of the deformable metal body 2 is designated in the illustration of FIG. 1 with t and is in the range of 0.2 to 1.2 mm.
• the pot-shaped metal carrier 1 of the sensor element 10 has formed said flange 3, whose axial thickness corresponds approximately to the material thickness t of the deformable metal body 2.
• the weld 4 is mounted so that it covers the entire
• the recess E ensures that the heat developed during welding by means of laser beam does not continue appreciably in the metal carrier 1, so that the weld seam 4 is spatially and thermally separated from the sensor system 5 (not shown) of the sensor element 10, which on the in FIG 1 left cover surface of the cup-shaped
• Embodiment is designed and described a pull tab; however, it could equally well be another measuring system element, e.g. a measuring axis or the like.
• Sensor element 10 is used, which has also formed a flange 3, which by means of a weld 4 with the surrounding metal body 2 is connected.
• the flange 3 is here as a radially extending portion of a cup-shaped
• Metal carrier 1 of the sensor element 10 is formed. Similar to the embodiment in Fig. 1 is also the here
• the adapted deformable metal body 2 so that both have approximately the material thickness t.
• the material thickness t can be between 0.2 and 1.2 mm.
• the sensor 5 of the sensor element 1 is further indicated, which is mounted on the left in Fig. 2 side on the cover surface of the cup-shaped metal carrier 1. The cover surface with the sensor 5 is at a distance h from the facing surface of the metal body 2 and the facing surface of the flange portion 3 of
• Metal carrier 1 is arranged. This distance h is like that
• Deformations of the deformable metal body 2 are optimized. Also in this embodiment, the weld 4 extends in the thickness direction completely through the
• FIG. 3 shows an arrangement of deformation-sensitive and deformation-insensitive ohmic resistors in FIG
• Wheatstone 'shear bridge circuit shown as the sensor 5 on the metal support 1 of the sensor element 10 in
• FIG. 3 shows a Wheatstone bridge with a total of six resistors A, B, C, D, E, F.
• the resistors A and B are mounted at right angles to each other, while the resistance groups D, E and C, F are also arranged at right angles to each other.
• the resistor group D, E is arranged parallel to the resistor B and the resistor group C, F is arranged parallel to the resistor A.
• the resistors A to H shown with connection points 11, 12, 13, 14, 15, 16 are connected.
• the taps 12 and 14 are arranged between the series resistors D, E and C, F, respectively.
• the bridge voltage is tapped between the contacts 13 and 16, while the pads 12 and 14 are used to detune the bridge.
• At least one of the resistors C or D is a deformation-sensitive resistive
• deformation-insensitive ohmic resistors are connected in series with their associated resistor D or C to form the respective bridge resistance.
• FIG. 4 shows the wiring of the Wheatstone bridge circuit shown in FIG. 4 on the left side of FIG. 4, which has already been explained in detail.
• the bridge circuit beyond the dotted line is mounted on the sensor, while to the right of this
• the external circuit is shown schematically.
• the resistors J, I and K are provided.
• K is an adjustable resistor or detuning resistor.
• the resistors I and J are connected in series with each other and in parallel with the resistors E and F.
• a tap 12 ' is provided, which is connectable via a switch a to the one end of the resistor K, the at its other end to the connection point 12 and the resistor I is connected.
• the present embodiment can be interrupted or turned off in series with the resistor J by the switch a, the parallel connection of the resistors I and K, so that only the resistors I and J in series with each other and in parallel with the resistors E and F are connected.
• This measure referred to as targeted detuning of the bridge, can now be used, in cooperation with a suitable evaluation unit, to evaluate the response of individual components to this signal change in such a way that a proper one can be evaluated
• the resistors E, F, I, J and / or K can be low-resistance resistors (approximately 20 to 200 ohms), while the resistors A, B, C and / or D can be high-impedance measuring resistors.
• the resistors A, B, C and / or D can be high-impedance measuring resistors.
• a quarter bridge only one of the bridge resistors is sensitive to deformation; in a half bridge are two bridge resistors
• FIGS. 5, 6, 7 and 8 each show schematized plan views of the cover surface of a sensor element with resistors applied thereto. They merely show the basic arrangement and orientation of the
• Bridge Resistors within each bridge are denoted by A, B, C, D, A ', B', C, D 'or A ", B", C' and D ", respectively.
• a so-called x- and y-directional arrangement of the bridges is shown, that is, the individual resistance pairs AC, A'C '; BD, B'D 'of the respective bridge are perpendicular to each other, with two pairs of bridges AC, A'C'; BD, B'D 'of two bridges are arranged parallel to each other. In this way, deformations or components thereof can be measured directly according to their offset by 90 ° to each other direction.
• Fig. 6 an arrangement is made in which the bridge resistors A, B, C, D of the left bridge are arranged in the same way as the resistors A, B, C, D in the left bridge in Fig. 5.
• FIG. 8 shows a further modification with a third Wheatstone bridge which, starting from the shape in FIG. 7, is arranged perpendicularly in the x-y direction between the bridges arranged at 45 degrees to the main axes x, y. That way is one

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

ID=42244458

Family Applications (1)

Country Status (2)

Cited By (2)

Families Citing this family (1)

Citations (8)

• 2009
  • 2009-09-30 WO PCT/IB2009/054276 patent/WO2011039567A1/de active Application Filing
  • 2009-09-30 CN CN200990100107.6U patent/CN202024769U/zh not_active Expired - Lifetime

Patent Citations (8)

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