RU1827013C - Tension measuring device - Google Patents

Abstract

The invention relates to measuring and control equipment, in particular for measuring non-electric quantities. Purpose of the invention. Reducing energy consumption. A strain gauge device comprises a strain gauge, an amplifier, a controlled scale converter and an adder, a power supply unit, the second output of which is connected to the second output of the power supply diagonal, the outputs of the measuring diagonal of the strain gauge are connected to the first and second inputs of the amplifier; the first scale converter; the output of which about connected to the third input of the amplifier, the second scale converter, the output of which is connected to the second input of the adder 4, the summing amplifier 7, the first output of which is connected to the inputs of the first and second scale converters, the second output - with the second input of the control scale converter and the first input - through the first resistor with the first output of the load cell diagonal. the first and second operational amplifiers are the second, third and fourth resistors, the inverting input of the third operational amplifier is connected to the first terminals of the fifth and seventh resistors, and the non-inverting input is connected to the first terminals of the sixth and eighth resistors, the second terminal of the seventh resistor is connected to the output of the third operational amplifier, the ninth resistor, the first output of which is connected to the inverting input of the third operational amplifier, and the second output to the first output of the power supply, the second output of the last connected with the second vertex of the load cell diagonal and is grounded, and the first output is connected to the non-inverting input of the first operational amplifier, the inputs of the first and second scale converters and the second output of the eighth resistor, the first output of the second resistor is connected to the non-inverting input of the first operational amplifier, and the second output to the output the second operational amplifier and with the second terminals of the fourth and sixth resistors, the first terminal of the first resistor is connected to the non-inverting input of the second Operation Nogo amplifier and the first terminal of the power pickoff diagonally and the second output - with an output of the first operational amplifier and to second terminals of the third and the fifth resistors, inverting inputs of the first and second operational amplifiers are connected together and to first terminals of the third and fourth resistors 1 yl. 00 s

Description

The invention relates to a measurement technique, in particular for measuring non-electric quantities under conditions of wide ranges and rapidly varying temperatures.

The purpose of the invention is to reduce energy consumption.

In Fig, 1 shows a diagram of the proposed device.

The device comprises a current sensor 1, an amplifier 2, a controlled scale converter 3, an adder 4, a power supply 5, an electronic ammeter 6, a summing amplifier 7, operational amplifiers 8-10, resistors 11-19, the first and second scale converters 20 and 21.

The measured signal from the output of the measuring diagonal of the load cell 1 is fed to the first and second inputs of the amplifier 2, then to the first input of the controlled power converter 3 and the first input of the adder 4, from the output of which the signal goes to the recorder (not shown in Fig. 2) . The signal from the first output of power supply 5 is fed to the inputs of the first 20 and second 21 scale converters, and from their outputs to the third input of amplifier 2 and the second input of adder 4, and the signal from the first output of power supply 5 is fed to the first input of electronic ammeter b and - second at its second input and the first input of the diagonal of the load cell 1. The electronic ammeter b generates a correction signal, which is fed to the second input of the controlled scale converter 3. The circuit is formed from the first 8, second 9 and third 10 opera of the amplifier, as well as the first 12, second 11, third 13, fourth 14, volume 16, sixth 17, seventh 18, eighth 19 resistor pax generates a signal proportional to the current through the strain gauge 1, and using the ninth resistor 15 is carried out compensation of the initial current value through the strain gauge 1.

Strain gauge device operates as follows:

The load cell 1 is affected by a measurable physical quantity and the accompanying temperature effect t.

The signal Lh at the first input of the controlled scale of the th th converter 3 can be represented:

Ui RKn (1 + am A t) + Ua «e А t K2 + Um - Р) 1J2 (1. +« м Л t) + Um (1 + Ур -% At).

5

5

0 5 0 5 0 5

0

5

where P is the measured physical quantity:

Ki - load cell conversion factor 1:

Kg is the conversion coefficient of amplifier 2;

At is the increment of temperature acting on the strain gauge 1;

U is the output voltage of the power unit;

u is the conversion coefficient of the first scale converter 20;

"M is the coefficient of the multiplicative sensitivity of the strain gauge 1 to the temperature increment Dt;

Ua Oa additive change in the zero output signal of the strain gauge 1 per unit temperature change;

Oa is the temperature coefficient of departure of the zero signal of the strain gauge 1.

The circuit of the electronic ammeter 6 responds to a current flowing through the first and second inputs. This current flows through the strain gauge 1. A distinctive property of the electronic ammeter 6 is that the voltage at its first input is repeated at its second input with an accuracy determined by the bias voltages of the first and second operational amplifiers 8 and 9. Therefore, with Using high-precision operational amplifiers, it can be stated that the voltage U taken from the first output of power supply unit 5 is repeated at the first output of the power supply diagonal of strain gauge 1, and the second input of electronic ammeter b is the source of direct voltage for the load cell 1. In this case, at the input of the electronic circuits of the ammeter 6, the voltage drop is zero and therefore does not lose a portion of the power voltage zhenii load cell 1 and is not reduced sensitivity.

If the values of resistors 11-14 are equal, the conversion function 1 of the electronic ammeter 6 can be written

Ua 2RK3,

where Ua is the output voltage of the electronic ammeter 6;

R is the resistance of the resistors 11-14;

C3 is the conversion coefficient of the summing amplifier 7 at the second inverting and third non-inverting inputs;

 is the current flowing through the feed diagonal of the load cell 1.

A change in the resistance of the diagonal of the power supply of the strain gauge 1 under the influence of temperature i will lead to a change (the supply voltage of the strain gauge remains stable) of the current I only through

strain gauge 1, and the output voltage of the electronic ammeter 6.

In the initial state, the voltage Ua °, caused by the flow of the initial current o through the strain gauge 1, is compensated by the signal U supplied to the first input of the summing amplifier 7. The adjustment is made by adjusting the value of the ninth resistor 15, To the fourth input of the summing amplifier 7 - there is a constant bias voltage U.

Thus, at the output of the summing amplifier, a signal Uz is generated:

U2 U (),

where Ut a. C3 is the change in the signal at the output of the summing amplifier 7 per unit temperature change At;

bKK temperature coefficient of sensitivity to temperature change At, controlled by the conversion coefficient of the summing amplifier 7 Kz at the second and third inputs, controlled by changing the values of the fifth and sixth resistors 16 and 17,

The voltage IJ2 at the second input of the controlled scale converter 3 determines its conversion coefficient K / j:

K4

TO

1 + Ut at KZ At

where K4 ° is the initial conversion coefficient of the controlled scale converter 3, determined by the value U of the initial constant displacement at its second input.

In order to correct both the additive and multiplicative errors of the main information signal Ui using an additional thermally dependent signal U2, the following conditions must be fulfilled:

p - Ua K2 n am-TG m0

Oh m-t t Kz

The values Ua, Ut, OM, "a," t are determined by experiment. Condition (1) is performed by adjusting the conversion coefficient um of the first scale converter 20

m

Ua z

U a

 - K2.

and condition (2) is performed by adjusting the conversion coefficient K3 of the summing amplifier 7 rjo to the second and third inputs.

K, -jy .. "Ut at

Controlled scale converter 3 implements the function

Ui., „PKiK2 (1 + Ohm At U2 1 4

+ (1 + - «(KZD

K2 U um

Uni (1 H-yfЈ2-% At) -K3

(1 + § «t КзДО Р Ki Ка КЗ + U щ К.

20 25

. thirty

35

about

e

fifty

gg

The residual additive bias UniK / j0 in expression (3) is eliminated using the adder 4 by adjusting the transform coefficient n2 of the second scale converter 21

P2 -P1K4 °.

Strain gauge output voltage

Suffer PKl K2 K4 °.

and functionally free from additive and multiplicative errors caused by temperature drift,

The technical and economic advantage of the proposed solution is that it reduces power consumption by simplifying the device.

Claims (1)

SUMMARY OF THE INVENTION A strain gauge device comprising a series-connected strain gauge, an amplifier, a controllable scale converter and an adder, a power supply unit, the second output of which is connected to a second output of the load cell diagonal of the strain gauge, the outputs of the load cell diagonal of the load cell are connected to the first and second inputs of the amplifier, the first scale converter, the output of which is connected to the third input of the amplifier, the second scale converter, the output of which is connected to the second input of the adder, summing the first amplifier, the first output of which is connected to the inputs of the first and second scale converters, the second output is connected to the second input of the controlled scale converter, the first input is connected through the first resistor to the first output of the load cell diagonal, the first and second operational amplifiers, the second, third and fourth resistors, the inverting input of the third operational amplifier is connected to the first terminals of the first and seventh resistors, and the non-inverting input is connected to the first terminals of the sixth and eighth p a resistor, the second output of the seventh resistor is connected to the output of the third operational amplifier, characterized in that, in order to reduce power consumption, it is equipped with a ninth resistor, its first output is connected to the inverting input of the third operational amplifier, and the second output is connected to the first output of the power supply , the second output of the power supply is connected to the second vertex of the load cell diagonal and grounded, and the first output of the power supply is connected to the non-inverting input of the first operational amplifier, the inputs of the first and large-scale conversion eaiel and the second terminal of the eighth resistor, the first terminal of the second resistor is connected to the non-inverting input of the first operational amplifier, and the second terminal is connected to the output of the second operational amplifier and the second terminals of the fourth and sixth resistors, the first terminal of the first resistor is connected to the non-inverting input of the second operational the amplifier and the first output of the load cell power diagonal, and the second output is connected to the output of the first operational amplifier and the second outputs of the third and fifth resistors, inverting - 15 Suitable inputs of the first and second operational amplifiers are connected together and to first terminals of the third and fourth resistors