UA11599U - Strain gage device - Google Patents

Abstract

The proposed strain gage device contains a bridge strain gage measuring circuit, a switching unit, an amplifier, an analog-to-digital converter, a computing unit, a power-supply unit, and a halfbridge reference circuit. The halfbridge reference circuit alternately replaces the halfbridge sections of the strain gage measuring circuit by the use of the switching unit.

Description

Description of the invention

The utility model belongs to the technique of measuring mechanical quantities and can be used for 2 measurement of mass, force, pressure, deformation and torque in various industries.

The closest to the proposed one is the strain gauge device, which consists of a series-connected first strain gauge and an amplifier, a first power source connected to the diagonal power supply of the first strain gauge, a series-connected second strain gauge, a switching circuit, a second amplifier, a "contactor" analog- differential converter and data processing unit, as well as the second power source and reference voltage unit 70. (A.s. Mo1814365, 50187/16).

The disadvantages of the device are its complexity, due to the use of an additional measuring channel and the need to control its performance, and the impossibility of separate control of the performance of the tension bridge of the main measuring channel.

The useful model is based on the task of simplifying the prototype device while maintaining the necessary 12 reliability of measurements and implementing a separate control of the tension bridge's performance.

To achieve the specified goal, a strain gauge device is proposed, which is a strain gauge, a switching circuit, an amplifier, an analog-to-digital converter, a data processing unit and a power supply, and in which, according to a useful model, an exemplary half-bridge is connected to the power supply parallel to the supply diagonal of the strain gauge, the output of which is connected to the first input of the switching circuit, to the second and third inputs of which the measuring diagonal of the strain gauge is connected.

The use of an exemplary half-bridge makes it possible to achieve a significant simplification of the scheme in comparison with the prototype device and to implement a separate control of the performance of the tension bridge.

Figure 1 shows the structural diagram of the strain gauge device.

Fig. 2 shows an example of the implementation of the switching scheme. 29 The tensometric device consists of a strain bridge 1, which is built on four tensor resistors glued to a sensitive element or research object. The power supply diagonal of the strain bridge is connected to the output of the power source 2, to which an exemplary half-bridge C is also connected, which consists of precision resistors 4 and 5 and a variable resistor 6. The output of the exemplary half-bridge is connected to the first input of the switching circuit 7, to the second and third inputs to which the measuring diagonal of the tension bridge is connected 1. Output Me. of the switching circuit is connected to the input of the amplifier 8, the output of which is connected to the input of the analog-to-digital Ge»! converter 9. The output of the analog-to-digital converter is connected to the input of the data processing unit 10, the control output of which is connected to the control input of the switching circuit 7.

The switching circuit 7 consists of electronic keys with normally open contacts 11, 12 and 13, and electronic keys with normally closed contacts 14 and 15. The input and output of the key 11 are connected to the second 32 and third inputs of the switching circuit. The inputs of the keys 12, 13 are connected and connected to the first input of the circuit - switching, the input of the key 14 is connected to the input of the key 11, the input of the key 15 is connected to the output of the key 11. The outputs of the keys 12, 14 and 13, 15 are paired with interconnected and connected to the outputs of the switching circuit. The control inputs of keys 11-15 are connected to the control input of the switching circuit, and the control inputs of keys 12, 14 and 13, 15 are connected in pairs. WITH

The device works as follows. Strain gauge 1 converts the measured mechanical value into an electrical signal. The voltage on the measuring diagonal of the tension bridge is equal to: ;з» Mykh - Мне щ- ' where Пн - OUTPUT voltage of power source 2; - that AR is the change in the resistance of the strain gauge resistors under the influence of the measured mechanical quantity; - K - the nominal resistance of the tensor resistors of the tension bridge.

The measuring diagonal of the tension bridge together with the output of the exemplary half-bridge Z is connected to circuit (9) of switching 7, which implements various combinations of their inclusion in order to control the performance of the tension bridge with 50. The output signal of the switching circuit is amplified by the amplifier 8 and fed to the analog-to-digital converter 9, where it is converted into a digital code, which is fed to the input of the data processing unit 10. The data processing unit processes measurement information, forms the output digital code of the device, and also controls the operation of the switching circuit 7 by applying a three-bit binary code to its control input and concludes about the operability of the tension bridge 1. During the operation of the device, the following states of the switching circuit are used: 1. "logic 0" is applied to the control inputs of all keys. In this case, the measuring diagonal of the strain gauge 1 is connected to the output of the switching circuit 7 s, and the voltage at the output of the switching circuit is equal to n, .- 2. The control inputs of keys 12 and 14 are supplied with a "logical 1", the control inputs of the other keys are supplied with a "logical 0 ". In this case, one of the half-bridges of the tension bridge 1 is replaced by an exemplary tension bridge 3, and at the output of the switching circuit 60 there is an additional voltage З". 3. A "logical 1" is applied to the control inputs of keys 13 and 15, and a "logical 0" to the control inputs of the other keys. In this case, the second half-bridge of tension bridge 1 is replaced by an exemplary tension bridge 3, and at the output of the switching circuit there is an additional voltage Ш". where For an operational tension bridge, the absolute values of the additional stresses are equal to each other:

Ч-- ЧИ Ak - I see t

RT NMA lived with

However, as a result of the deviation of the initial resistance and sensitivity of tensor resistors from the nominal values, as well as the time and temperature drift of these parameters, the absolute value of the difference l of additional voltages can be 0.05V.

Possible failures of the tension bridge are - a break in the connecting conductors; - destruction of the strain gauge; 70 - detachment of the tensor resistor from the sensitive element or research object.

The first two failures are easily identified, because the output voltage of the tension bridge in this case exceeds the limits of possible values during normal operation. Exfoliation of the tensor resistor, which leads to a complete or partial loss of its sensitivity, cannot be determined without applying a sample value of the measured value to the input of the device. t With a complete loss of sensitivity of one of the tension resistors, the voltage on the measuring diagonal of the tension bridge is equal to m -t ZAKO.

EMYZH 7 U ZIE aa

The values of the additional voltages in this case are 'AN,

ИШи - Mt Z иш - AK . 4-2 -

The absolute value of the difference between them is equal

M - MA. zva in t them

AKA

(22)

The control of the working capacity of the tension bridge is carried out as follows. During device calibration, a sample half-bridge is balanced. For this purpose, the control inputs of the electronic keys 11, 12 and 14 are supplied with a "logical 1", i.e., at the output of the switching circuit - an additional voltage U, and the measuring diagonal of the tension bridge 1 is shortened. By adjusting the variable resistor 6, the zero value of M is reached". The nominal resistances of the precision resistors 4, 5 and the variable resistor 6 should be selected in such a way that - k4-k5nO.5Kv, "- kb-0.02ka4.

During the operation of the device, the data processing unit 10 periodically monitors the operability of the tension bridge, changing the state of the switching circuit 7 in such a way that at its output there are additional voltages В and 0". After amplification and analog-to-digital conversion of the additional voltages, the data processing unit 10 calculates a digital "

The code corresponding to the difference in the absolute values of the additional voltages. If the received code exceeds the permissible c value, which corresponds to |d|- 005, the data processing unit makes a decision to peel off the tensor "» and issues the corresponding signal. The advantages of the presented device compared to analogues are: "- significant simplification of the circuit; - the possibility of separate control of the working capacity of the tension bridge.

Claims (1)

- Formula of the invention - o Strain gauge device, which includes a strain gauge, a switching circuit, an amplifier, an analog-to-digital s 50 converter, a data processing unit and a power source, which is distinguished by the fact that an exemplary half-bridge is connected to the power source parallel to the power supply diagonal of the strain gauge, the output of which 'united with the first Me) by the input of the switching circuit, to the second and third input of which the measuring diagonal of the tension bridge is connected. with 60 b5