SU1303851A1 - Device for measuring temperature and strain - Google Patents

Abstract

This invention relates to measurable. technology and improves measurement accuracy. The device contains a stabilized current source 1, an exemplary resistor 2, thermocouples 3 and 4, a switch 5 with a control unit 6, operational amplifiers 7-10 and resistors 1-1-18. The introduction of new elements and the formation of new connections between the elements of the device allows reduce the impact on the measurement result of the resistance of the connecting wires. With this switching circuit of operational amplifiers 7-10, they have a high input impedance, so the measurement result does not depend on the resistance of the wires through which the operational amplifiers 7-10 are connected to the reference resistance 2 and thermopower transducers 3 and 4, and the transient resistances of the switch 5. 1 silt § (L with about 00 00 ate

Description

This invention relates to a measurement technique and is intended to measure temperature and strain.

The aim of the invention is to increase the measurement accuracy by reducing the influence on the measurement result of the resistance of the connecting wires.

The drawing shows a diagram of the device.

The device contains a stabilized current source 1, an exemplary resistor 2, the first 3 and the second 4 thermal thermocouples, a switch 5 with a control unit 6, four operational amplifiers 7-10, each of which is covered by one hundred percent negative feedback, and eight resistors 11-18 with the same resistance R. Thermocouples 3 and 4 must have the same initial resistance, the same temperature coefficients and the same strain-sensitivity coefficients. At the same time, they should be fixed on the object in such a way that, when subjected to deformation, the resistance of one of them increases by the value of LCd, and the resistance of the other decreases by the value of LC.

The device in the temperature measurement cycle operates as follows.

In the conditional conditional zero temperature state, each of the thermal converters 3 and 4 has the resistance value RQ. The resistance value of the reference resistor 2 is chosen to be 2R. The findings of these

The terminals are connected to the operational terminals 40 from the output of the amplifier 8, and to the noninventers 7, 8, and 10 by means of a switching input - voltage from the sample 5, to which the corresponding resistor 2 is fed the signal from block 6 of controllers 3 and 4 and connecting ports are as follows: potentials 23–25, resulting in no. pins 19 and 20 of exemplary resistivity; its output is formed by the voltage, the torus 2 is respectively non-ventilation linearly related to the measured temperature

operating inputs of operational amplifiers 7 and 8, the first potential output of thermal strain gauge 3 to the non-ventilation input of the operational amplifier 10. By the potential 24 volt output of the voltage converter 4 is permanently connected to the noninventing input of the operational power 9. In connection with the resistance of the thermotentonoconverter 3 experiencing tensile deformation changes by the value - & Rj ,, and the resistance of the thermothene transducer 4,

and,

 -41.

U R.

50 where i

st

 EXIT T

- stable current generated by a stable source of 2 current.

In the tact of measuring the deformation with the power of switch 5, only potential terminals 21, 26 and 27 are connected to the operational amplifiers 7, 8 and 10, respectively. In this case, the output of the operational amplifier 9

five

0

experiencing compressive deformation - on iRjjj, then the total resistance of thermocouples 3 and 4 does not depend on the deforming effect. With a change in temperature, the resistance of each of the thermocouple transducers changes by the value of UR. With this switching circuit of the operational amplifiers, they have a high input resistance, so the measurement result does not depend on the resistance of the wires through which the amplifiers are connected to the reference resistance and thermal strain transducers, and the contact resistances of the switch. Operational amplifier 10 operates according to the scheme of a non-ventilating amplifier with a gain of 2. Its input is supplied with voltage from a thermottender 4 and a connecting wire 23. The input amplifier of the third operational amplifier 9- is affected by the voltage from the output of the operational amplifier 10, and non-inverting input is a voltage proportional to the resistance of the connecting wire 23, as a result of which a signal is generated at its output proportional to the resistance of the thermal strain gage 4. It is a voltage It goes to the noninventing input of the second operational amplifier 8, to the inverting input of which voltage is applied to the thermocouples 3, 4 and connecting wires 23-25. The voltage input is fed to the input input of the first op amp.

five

and,

 -41.

U R.

I

st

 EXIT T

- stable current generated by a stable source of 2 current.

In the strain measurement cycle with the POWER of switch 5, only potential terminals 21, 26 and 27 are connected to operational amplifiers 7, 8 and 10, respectively. In this case, the output of operational amplifier 9 generates a signal proportional to the resistance of thermal to voltage converters 4, and output of amplifier 7 is a signal linearly related to the measured strain.

-41

st

uR,

and independent of the resistance of the connecting wires 23-25.

Claims (1)

Invention Formula A device for measuring temperature and strain, containing a series-connected model resistor, the first and second thermal strain gages connected to the first and second outputs of the current source, two operational amplifiers, four resistors, characterized in order to improve the measurement accuracy by reducing the effect on the result of measuring the resistances of the connecting wires, two additional amplifiers, a resistor circuit, a control unit and a switch, the control input of which o connected to the control unit, the first and third inputs are connected to potential leads of the reference resistor, the second and fourth inputs are connected to the first potential output of the first thermo Editor E. Sligan Compiled by V.Kulikov Tehred A. Kravchuk Order 1298/41 Circulation 777 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 fO f5 20. 30 25 transducer, the second potential output of which is connected to the fifth input of the switch, the first and second outputs of the switch are connected to the non-ventilation input of the first operational amplifier, the third and fifth outputs are connected to the non-ventilation input of the second operational amplifier, the sixth input of the switch is connected to the first potential output of the second thermotensoprotector, the second potential output of which is connected to the noninventing input of the third operational amplifier, and the fourth and sixth outputs are connected With a noninventing input of the fourth opamp, the output of the first opamp is connected via a chain of all resistors connected in series to a zero-potential busbar and to a second output of the current source, to the inputs of the first, second, third, and fourth op-amps, respectively, to dots connections of the first and second, third and fourth, fifth and sixth, seventh and eighth resistors, and the outputs of the second, third and fourth operational amplifiers us, respectively, with connection points of the second and third, fourth and fifth, sixth and seventh resistors. Proofreader A.Zimokosov