SU1679224A1 - Strain-measuring device - Google Patents

Abstract

The invention relates to mass and force measuring equipment and can be used to create precision weights, dynamometers for medical clinical diagnostic equipment. The purpose of the invention is to improve the measurement accuracy and simplify the electrical device (12). The force of the load placed on the load-carrying platform 1 is transmitted through the protrusion 12 of the body of each autonomous strain-gauge unit 2 to its elastic element 4. The deformation of the elastic elements 4, proportional to the load, is measured using strain gauges 5-8. The resulting signal of the measured parameter, obtained by sequential and consonant summing of the signals of autonomous strain gauge nodes 2 in the bridge or half-bridge circuit of the device, comes from the pins of the bridge to an external measuring device. The device provides for the possibility of radial movement of each of the supports 3 with the strain gauge assembly 2 in the plane of the platform 1 by means of the grooves 11 and fixing in a predetermined position with screws 13 to provide correction of the conversion factors of the strain gauge assemblies 2. 6 Il. (L S p | p about h | yu yu 4

Description

9 7

3 8 10

1

The invention relates to mass and weight measuring techniques and can be used, for example, in creating precision scales, dynamometers for medical clinical diagnostic equipment.

The purpose of the invention is to improve the measurement accuracy and simplify the electrical circuit of a multi-support strain gauge device.

FIG. 1 is a schematic diagram of a three-support strain gage mass measurement device; in fig. 2 is the same, top view; in fig. 3 - functional device diagram; Figures 4 and 5 illustrate the connection of the strain gauges of the thermometric nodes into a single pavement and half bridge, respectively; FIG. 6 is a graph of the output signal of the device versus strain for the proposed and known devices.

The strain gauge device (Fig. 1) consists of a cargo-receiving platform and autonomous strain gauge nodes 2 placed on supports 3. Each strain gauge node 2 contains an elastic element 4, for example, in the form of a two-beam spring, on which tensor-resistance converters 5-8 are installed .

In this case, if we take the strain gauges 5 and 6 (Fig. 1 and 3), placed on the working arms 9 and 10, respectively, of each elastic element 4 for the strain gauges with positive resistance deviation, then the corresponding resistance strain gauges 7 and 8 will have a negative resistance deviation when a load is applied to a silo-sensing platform 1.

The supports 3 with autonomous strain gauge units 2 fixed on them are mounted on the periphery of the power-receiving platform 1 (Fig. 2) symmetrically with respect to its geometric center 0 and can be moved in the plane of application of forces (in the plane of platform 1) towards the geometric center O of platform 1 and back, as well as with the possibility of fixation in the desired position.

The possibility of moving the supports 3 with autonomous strain-measuring nodes 2 fixed on them is realized by making in the platform 1 of the guide radial grooves 11 (according to the number of the supports 3) equidistant from the geometric center 0 of the platform 1 and symmetric to it, in which the protrusions of the 12 buildings tensometric nodes 2.

In a device with a three-support platform 1, the grooves 11 are located at the vertices of an equilateral triangle equidistant from the center 0 of the platform 1, and the axes of the grooves 11 are aligned with the direction (the corresponding radii of the platform 1. The length of the grooves 11 is selected taking into account the possible initial technological variation of the characteristics of the elastic elements 4 and strain gauges 5-8 individual strain nodes 2 and lies within 1-2% of the corresponding radius.

The possibility of fixing the position of the supports 3 with autonomous strain gauge units 2 is realized by means of fixing screws 13 (or nuts).

The strain gauges 5-8 of all autonomous strain gauge nodes 2 are connected into a single pavement (half-bridge) circuit (Fig. 4 and 5), and the strain gauges 5 with positive dividing resistance of all autonomous nodes 2 are connected in series to one shoulder of the bridge, the opposite shoulder of which is also connected in series connected resistance strain gauges b with positive deviation resistance of all autonomous nodes 2, and adjacent bridge arms include, respectively, all strain gauges 7 and all strain gauges 8 with the opposite sign devi tion resistance.

Thus, each bridge arm (half-bridge) of the strain gauges of all autonomous teuzouzl 2, and each shoulder have a consistent and equal on resistance sign of the resistance, and the adjacent shoulders of the bridge (half-bridge) are distinguished by the sign of the deviation of the resistance of the strain gages. Bridges or half-bridge circuits operate with a source of 14 power.

When setting up the device during its assembly, the conversion coefficient in each autonomous strain gauge unit 2 is corrected. To do this, the strain gages 5–8 of each autonomous unit 2 are connected to their bridge circuit for the correction time of the conversion factors. Platform 1 is loaded with calibrated weights (.), Providing equal increments of mass. For each specific load, output signals are measured for each of the autonomous units 2 and compared with each other. To obtain the same values of the conversion factors of the autonomous units 2, they are moved together with the support 3 along the geometric radius of the platform 1 by sliding the protrusion 12 in the guide groove 11 to achieve equal values of the increment of the output signals of these nodes during loading. Then the position of autonomous

nodes 2 with supports 3 are fixed with screws 13, and strain gauges 5–8 of all autonomous nodes 2 are connected to a bridge (half bridge) circuit (Fig. 4 and 5).

FIG. 6 shaded the area of the characteristic 5U2 (AI) of a separate tensing node when moving its direction to the geometric center 0 of the board: form 1 and back along the guide groove 11. The width of the region corresponding to the length of 10 not the groove 11. lies within approximately ± 2 % of the nominal value of the slope conversion.

The device works as follows .15

A load (for example, a bed with a patient) is placed on platform 1, trying to locate it closer to the geometric center of the O platform. The force perceived by the platform 1 is transmitted through the protrusion 12 of the housing of each autonomous strain gauge assembly 2 to its elastic element 4.

The deformation of the elastic elements 4, proportional to the load, is measured using strain gages 5-8, which convert 25 the deformation into an electrical signal.

The result of the information on the measured mass (force) for all autonomous units 2, obtained by sequentially and consistently summing the signals of the individual tensor nodes 2 in the bridge (half-bridge) circuit of the device, comes from the AUS bridge (half-bridge) terminals to if necessary, amplifying the output signal and converting it into the required shape.

The resultant marriage signal D formed by successive and consonant summation of 40 voltages AU | separate autonomous measuring nodes 2, equal to -AU,

where t is the number of measuring nodes in the system.

Subject to that. what. DU | n nam (. we get

 -ARi -tJ,

where t.p.50

Considering that the device conversion rate

 whether tag55

Kn

where Im is the magnitude of the linear deformation of the elastic element, the achieved gain A in increasing the conversion coefficient, as the ratio of the conversion coefficients in the proposed Kn (n) and known Kn (and) measurement systems, will be

-) To „(and)

Ic-ari -3 n ari -3 aln

 rn

Thus, the strain gauge device, without the use of additional technical means, provides, in comparison with the known m-fold increase in the resultant conversion factor Kp, with the same amount of elastic deformation and feed current of the resistance strain gages with the possibility of correcting the slope of the characteristic of the measuring unit.

Claims (1)

Invention Formula A strain gauge device containing a multi-support symmetrical power-receiving platform with autonomous strain gauge nodes in the form of elastic elements placed in supports and strain gauges with opposite signs of resistance deviation on each working arm of the elastic element included in bridge circuits, characterized in that, in order to improve the accuracy of measurements and simplify the electrical circuit of the device, strain gauges of autonomous tensometric nodes are connected into a single bridge or half bridge circuits, in each arm of the bridge circuit an equal number of strain gauges of each autonomous strain gauge assembly are connected in series and equally according to the sign of resistance deviation, and adjacent straps of the circuit are placed strain gauges with opposite resistance deviation signs, with each elastic element supported with radial displacement in the plane platform and fixing its position. // 13 eleven 15 15 eleven 1 5 5 // v u Xy 3S  ////BUT X1 / // ///// w /////////13873873 FIG. 2 U Mi S S X1 0to.J FI.5