SU1368621A1 - Integral strain-measuring bridge and method of adjustment thereof - Google Patents

Abstract

The invention relates to strain gauges and can be used to create sensors of mechanical quantities based on temperature-compensated integral strain gauge bridges. The purpose of the invention is to increase the accuracy under the conditions of non-uniform temperature field by reducing the additive temperature error, which is achieved by performing each arm of a bridge of two resistors with different sign temperature coefficients of resistance and the corresponding setting.

Description

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bridge at two different temperatures, with one of the strain gauges in one of the arms refined to obtain temperature compensation for the bridge and two other strain gauges in the adjacent shoulder to obtain the required balancing of the bridge with a laser beam. The integral strain gauge bridge contains strain resistors 2–9, contact pads 10–1.5 to them, breaks and re-installed jumpers 16 and 17, instead of which, for the tuning time, connect variable resistors 18 and 19. Each pair of strain gages 2 and 3, 4, 5, 6 and 7 , 8 and 9 are made of materials with temperature coefficients of resistance of opposite signs. The integral strain gauge bridge and the method of its adjustment allows to reduce the temperature error and reduce the sensitivity of the bridge to thermal shock. 2 sec. f-ly, 1 ill.

one.

The invention relates to a measurement technique and can be used to measure mechanical quantities by electrical methods.

The aim of the invention is to improve the accuracy under the conditions of non-uniform temperature field by reducing the additive temperature error, which is achieved by performing each arm of a bridge of two resistance strain gages made of materials with temperature coefficients of resistance of opposite signs and corresponding adjustment of the bridge at two different temperatures with one of the strain gauges in one of the arms until a temperature compensation is obtained for the bridge and two other strain gauges in the adjacent leg required to balance the bridge with a laser beam.

The drawing shows the electrical circuit of the integral strain gauge bridge.

Integral strain gauge bridge formed on membrane 1 contains two identical chains of four series-connected resistance strain gages 2, 3, 4 and 5, 6, 7, 8 and 9, six contact pads 10. 15 located respectively at the ends and in the middle point of each chain and two torn and newly installed jumpers 16 and 17 in the process of adjustment, each of which connects the respective free ends of both circuits. Each pair of strain gages 2iZ, 4i5, 6i7, 8i9,

included between two adjacent pads 10 and 11, 11 and 12, 13 and 14. 14 and 15, made of two different materials with temperature coefficients of resistance of opposite signs. At the time of tuning the bridge, instead of switching 1 16 and 17, variable resistors 18 can be connected

and 19.

Integral strain gauge bridge works in the following way.

When loading the strain gauges formed on the membrane 1, a mechanical parameter and when connecting the power to the pads 11 and 14 on the output diagonal with closed jumpers 16 and 17, an output signal appears that is proportional to

the value of the mechanical parameter.

Since each of the 2 and 3, 4 and 5, 7 and 8, 8 and 9 tensor coupler pairs is chosen in such a way that the increment of resistance from the temperature of one is equal to the increment in the absolute value of the other and has the opposite sign, this allows

30 self-compensation of the temperature change of resistances in the arms of the strain-gauge bridge, and consequently, reduce the additive temperature error when the sensor is operated under conditions of an uneven temperature field.

The method for setting up an integral strain gauge bridge is implemented as follows.

35

The resistances of the strain gauges 2–9 and their temperature coefficients of resistance are determined. Connect pads 15 and 10, 12 and 13 with jumpers 16 and 17. Apply a supply voltage to the measuring bridge and record the initial value of the output signal at a certain temperature, for example, in normal topics - | Q level of the output signal of the bridge.

Peruational conditions. The temperature on the substrate is integrally modified by the strain gauge bridge to a predetermined value and by the sign of the change in the initial output signal of the bridge from the temperature of 15 arms using the formulas that determine the resistance strain gauge with a temperature resistance coefficient which decreases with increasing resistance of the strain gauge and changes the adjustment resistor value 19 and disable it. Calculate the resistance values of each strain gauge 5 and 4 in

R.

lkt- o .;

and

 - lkt-o ;;

outside, for example, a strain gauge 2.

The jumper closest to the detected strain gauge, for example, 16, is broken, and a variable resistor, for example, resistor 18 is connected to the same bridge arm instead. Under normal conditions, the resistance of the variable resistor 18 is changed to obtain an output signal equal to the initial output signal for a given temperature This resistance is measured and the variable resistor is disconnected. Calculate the resistance value of the modified strain gauge 2 according to the formula

R, i ARr

iv ()

where r

Xi

magnitude of resistance, which increase the strain gaugeJ

L R - the magnitude of the change in resistance of the variable resistor i

T - initial temperature

(normal temperature conditions)

T is the predetermined temperature to which the temperature of the substrate of the integral strain gauge bridge is changed.

The detected strain gauge 2 is modified by removing a portion of the strain gauge material 2, for example, with a laser beam. Repair jumper 16

and the magnitude and sign of each 55 additive temperature error of the bridge is measured. By the sign of the signal, you determine a pair of strain gages of one of the bridge arms, which, with an increase in the total resistance, reduces the magnitude of the initial output signal, for example, a pair of tensors 4 and 5.

Break the jumper closest to the identified pair, for example jumper 17, and switch on a variable resistor 19 instead. Change the resistance of the variable resistor 19 to a given arm by the formulas

The value of the adjusting resistor 19 is measured and disconnected. Calculate the resistance values of each strain gauge 5 and 4 in the detected

15 shoulders by formulas

R.

lkt- o .;

and

0

R

 - lkt-o ;;

25

Xi

V; -Y;

five

where and r

Ki

 Xi

0

resistance of the strain resistors in the identified shoulder of the bridgeJ oi; and oij are the temperature coefficients of resistance of the strain gauges. The extracted pair of strain gauges 4 and 5 is refined by removing some of the material of the strain gauges, for example, with a laser beam, and the jumper 17 is restored.

The proposed strain gauge bridge and its adjustment method allow to increase the measurement accuracy in a wide range of irregular temperatures. In addition, this technical solution makes it possible to reduce the sensitivity of the integral tensometric bridge to thermal shock.

Claims (2)

1. Integral strain gauge 5 bridge, containing two identical chains of three series-connected strain gauges, each of which is made, with contact pads at both ends of the first strain-0 torus and the free end of the third strain gauge, which distinguishes x: under conditions of non-uniform temperature field due to diminution, it is equipped with two additional strain gauges, each of which is connected in series with the first strain gauge in the corresponding 5 The connecting circuit between the free end of this strain gauge and its contact pad, and each pair of strain gauges connected between two adjacent contact pads, is made in the form of two strain gauges with temperature resistance coefficients of opposite signs. 2. The method of setting up an integral strain-gauge bridge, which consists in measuring the initial output signal of the bridge for two different temperatures and changing the resistance of the modified resistor in one of the arms of the bridge, which is different in that before measuring the initial output signal of the bridge the extreme points of both circuits by jumpers, according to the sign of the change in the initial output signal of the bridge from the temperature, determine the modified strain gauge with a temperature coefficient of resistance which, when the resistance of the resistor increases, reduces this change at one of these temperatures, breaks the jumper closest to this strain gauge and turns on ten 686216 At the same bridge bridge, the variable resistor changes its resistance until the output signal of the bridge is equal to the initial output signal at the second temperature, this resistance is measured and the resistor is disconnected, the resistance of the resistance strain gauge is calculated and its resistance is increased to the calculated value by removing some of the material the strain gauge, restore the jumper, measure the magnitude and sign of the output signal of the motor, and determine the sign of the pair of strain gauges by the sign, which the mm resistance reduces this value, breaks the jumper nearest to this pair and includes 2Q instead of it, the variable resistor is changed at the same arm, its resistance is changed to a given level of the output signal of the bridge, the resistance is measured and the resistor is disconnected, the resistance values of each resistance strainer in the pair are calculated, the resistances of these strain resistances are increased to the calculated values by removing part material and rebuild the jumper again.