RU2507477C1 - Method to tune strain-gauge sensors with bridge measurement circuit by multiplicative temperature error with account of positive non-linearity of temperature characteristic of output signal of sensor - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: at load resistance R_L≥500 kOhm they determine a temperature sensitivity coefficient (TSC) of a bridge circuit α⁺ _do and α^- _do at temperature t⁺ and t^-, corresponding to upper and lower limit of the working temperature range, and non-linearity of bridge circuit TSC (Δα_do=α⁺ _do-α^- _do). If the produced value Δα_do is positive, they convert the positive non-linearity of the bridge circuit TSC into the negative one by inclusion of a heat-independent resistor R_i into a diagonal of power supply and simultaneous shunting of inlet resistance with a heat independent shunt, which is formed by serial inclusion of a heat-independent resistor R_αinp and a heat-independent resistor R_dinp. For this purpose they determine input resistance and TSC of input resistance, and also TSC of resistance strain gauges α⁺ _d and α^- _d at temperature t⁺ and t^-, and they calculate non-linearity of bridge circuit TSC (Δα_d=α⁺ _d-α^- _d). If α⁺ _d and Δα^- _d are in the field of conversion of positive non-linearity of bridge circuit TSC into the negative, then they take the nominal value of the heat independent shunt equal to input resistance, and the nominal value of the resistor R_i. as equal to 100 Ohm. They calculate nominal values of resistors R_αinp and R_dinp. They connect resistors R_i, R_αinp and R_dinp into the diagonal of bridge circuit power supply. The TCS of the bridge circuit is defined at the temperature t⁺ and t^-, non-linearity of the bridge circuit TCS is calculated as Δα_do. If Δα_do takes the negative value, then compensation of multiplicative temperature error is carried out with account of negative non-linearity of bridge circuit TSC by inclusion of a heat independent resistor R_αoutp, shunted with a heat independent resistor R_doutp, into the output diagonal of the bridge circuit under the resistance of the load R_L≤2 kOm.

EFFECT: higher accuracy of compensation.

2 tbl, 2 dwg

Description

The invention relates to measuring equipment and can be used to configure the strain gauge sensor equipment with a bridge measuring circuit for a multiplicative temperature error.

There is a method of tuning strain gauge sensors with a bridge measuring circuit for a multiplicative temperature error taking into account the non-linearity of the temperature characteristic of the sensor output signal (see Patent for invention RU 2443973 C1, G01B 7/16 "Method for setting strain gauge sensors with a bridge measuring chain for a multiplicative temperature error, taking into account nonlinearity of the temperature characteristics of the sensor output signal ", published on February 27, 2012 in Bull. No. 6), adopted as a prototype, in which to compensate tiplikativnoy temperature error at load resistance R _n> 500kOm determine TCF bridge circuit and _do α ⁺ α ^- _up to the temperature range Δt ⁺ = t ⁺ -t ₀ and Δt ^- = t ^- -t _0, where t ₀ ⁺ t, t ^- - normal temperature, upper and lower limits of the operating temperature range, respectively. Calculate nonlinearity TCF bridge circuit (Δα = α ⁺ _{do do} -α ^- _w). If Δα _to takes a negative value, then the sensor is connected to a load of R _n ≤2kOhm. Determine the output resistance of the bridge circuit, TCS output resistance of the sensor. Check if the _DC link bridge circuit and its nonlinearity are found in the field of application of the method, if these sensor parameters are in the field of application, calculate the required value of the thermally dependent resistor R _αout and the thermally independent resistor R _two , install the resistor R _αout , shunted by the thermally independent resistor R _two , in series with the load.

The reasons that impede the achievement of the technical result indicated below when using the known method include the fact that the non-linearity of the DC circuit of the bridge circuit can take both negative and positive values, as shown in the description of the prototype. The prototype allows for full compensation of the multiplicative temperature error, taking into account the negative nonlinearity of the DC circuit of the bridge circuit, satisfying the inequality Δα _to ≤2 · 10 ^-6 1 / ° С. In the description of the prototype it is also shown that the lack of consideration of the non-linearity of the TCF bridge circuit allows compensation of the multiplicative temperature error at one extreme point of the operating temperature range, for which the values of the compensation resistors R _αout and R _{two were calculated} , which allows to obtain a multiplicative sensitivity of the sensor to a temperature within ± 1 · 10 ^-4 1 / ° С at a given point of the operating temperature range. At the other extreme point of the operating temperature range, the multiplicative sensitivity of the sensor to temperature is about ± 2 · 10 ^-4 1 / ° С and more, exceeding the permissible value, which is ± 1 · 10 ^-4 1 / ° С.

The invention consists in the following.

The task to which the claimed invention is directed is to develop a method for tuning strain gauge sensors with a bridge measuring circuit by a multiplicative temperature error, which would improve the accuracy of compensating for a multiplicative temperature error in the setup process with a positive non-linearity of the DC-circuit TCD.

The technical result consists in increasing the accuracy in the process of tuning strain gauge sensors with a bridge measuring circuit by a multiplicative temperature error with a positive nonlinearity of the DC circuit of the bridge circuit.

The specified technical result in the implementation of the invention is achieved by preliminarily converting the positive nonlinearity of the DTC of the sensor bridge circuit into negative and subsequent compensation of the multiplicative temperature error in accordance with the prototype.

This is achieved by the fact that in real sensors, to adjust the sensitivity, a thermally independent resistor R _{i is} included in the diagonal of the bridge circuit power. To convert the positive nonlinearity of the DC current bridge circuit to the negative parallel to the input resistance of the bridge circuit, include a thermally dependent resistor Rα _in and a thermally independent resistor R _dvx , which are connected to each other in series, which gives a shift in the nonlinearity of the _{DC current} circuit of the sensor bridge to negative values. The ratio of the values of the thermally dependent resistor Rα _in and the thermally independent resistor R _{dvx is} chosen based on the need to ensure the negative nonlinearity of the DC-link circuit Δα _to ≤2 · 10 ^-6 1 / ° С, at which it becomes possible to use the prototype. To do this, if the non-linearity of the DC current factor of the bridge circuit is positive, for R _n > 500 kOhm, the TCD of the strain gages α ⁺ _d and α ^- _{d are} determined for the temperature range Δt ⁺ and Δt ^- respectively, and the nonlinearity of the TFC of the strain gages Δα _d = α ⁺ _d- α ^- _d . Determine the value of the input resistance R _I , TCS input resistance α ⁺ _I , α ^- _I for the temperature range Δt ⁺ and Δt ^- respectively. Check the affiliation of α ⁺ _d and Δα _{d of} the transformation region of the positive nonlinearity of the DC coupler of the bridge circuit into negative. If α ⁺ _d and Δα _d satisfy the domain of converting the positive nonlinearity of the DC-link circuit of the bridge circuit into negative, then by analogy with the prototype, the value of the thermally independent resistor is taken to be 100 Ω, since the value of the thermally independent resistor R _i in real sensors is from 10 Ω to 200 Ω. The resistance of the shunt formed by the serial connection of the thermally dependent resistor Rα _in and the thermally independent resistor R _dvc is taken to be the input resistance of the bridge circuit, since lower values of the shunt will lead to an excessive decrease in sensitivity, which will complicate the subsequent adjustment of the sensor for sensitivity. The value of the thermally dependent resistor Rα _in and the thermally independent resistor R _{dvh are calculated} . Install the resistor R _i in the diagonal of the power supply of the bridge circuit. In parallel with the input resistance include resistors Rα _in and R _dvh , connected to each other in series. The DC circuit of the bridge circuit and its nonlinearity are calculated after the inclusion of the resistors R _i , Rα _in and R _dvh in the diagonal of the power supply of the bridge circuit. If the nonlinearity of the DC-circuit TCD takes a negative value, then further compensation of the multiplicative temperature error is made in accordance with the prototype.

The invention is illustrated by drawings, where Fig. 1 shows the domain of conversion of the positive nonlinearity of the DC coupler of a bridge circuit into a negative one, Fig. 2 is a diagram of the connection of resistors R _i , Rα _in , R _dvh , R _αout , R _two .

The method is as follows.

As shown in the description of the prototype, the nonlinearity of the DC circuit bridge circuit includes two components:

1. non-linearity introduced by strain gauges mounted on an elastic element, which can take both negative and positive values;

2. non-linearity introduced by the measuring circuit, which is always negative when using a bridge circuit.

In accordance with paragraph 2, it is possible to obtain a negative non-linearity of the DC-link circuit of the bridge circuit by changing the non-linearity component of the DC circuit of the bridge circuit introduced by the measuring circuit.

In accordance with the description of the prototype in the presence of a thermally independent resistor R _i included in the power supply bridge

circuit, the dependence of the supply voltage will take the form:

where U _o is the output voltage of the bridge circuit when exposed to temperature;

U _pit is the supply voltage of the bridge circuit;

k = R ₁ / R ₂ = R ₃ / R ₄ is the symmetry coefficient;

R _I - input resistance of the bridge circuit of the sensor;

α _I - TCS input resistance;

Δt = tt ₀ - temperature change; - TKH strain gages;

R _i is the nominal value of a thermally independent resistor included in the power circuit;

t is the acting temperature;

t ₀ - normal temperature;

ε _j is the relative change in shoulder resistance R _{j of the} bridge circuit.

Analysis of the denominator of dependence (1) allows us to conclude that, after turning on the resistor R _i , the dependence of the supply voltage on temperature will have a component inversely proportional to the temperature increase, which will lead to a shift in the nonlinearity of the DC-link circuit of the bridge circuit to negative values, which increases with the growth of TCS input resistance, which is confirmed by the prototype.

To increase the TCS of the input resistance, you can turn on a temperature-dependent shunt parallel to the input resistance of the bridge circuit. The value of the shunt should be taken not less than the input resistance of the bridge circuit, as shown above. In the future, we assume that the resistance of the thermally dependent shunt is equal to the input resistance of the bridge circuit (Rα _in + R _dvh = R _in ).

Let us derive the dependence of the nonlinearity of the DC-link circuit of the bridge circuit. When exposed to temperature, the resistance of the shunt will be:

where R _Wt is the resistance of the shunt formed by sequentially turning on the resistor Rα _in and R _dvh , when exposed to temperature;

α _to - TCS of the thermally dependent resistor Rα _in ;

Δt = tt ₀ - temperature change;

t is the temperature at which the measurement is made;

t ₀ - normal temperature.

Shunt resistance when exposed to temperature can also be represented as follows:

where α _W - TCS thermally dependent shunt.

Equating the right-hand sides of equation (2) and (3), taking into account (1), we can derive the dependence of the TCS shunt on the value of the resistor Rα _in and R _dvh :

The value of the input resistance of the bridge circuit after shunting, taking into account the equality of the input resistance of the bridge circuit and the resistance of the temperature-dependent shunt, will be:

The input resistance of a shunted bridge circuit when exposed to temperature can be represented as follows:

The input impedance of a shunted bridge circuit can also be represented as follows:

where α _vhsh - TCS input resistance of a shunted bridge circuit.

Equating the right-hand sides of equation (6) and (7), taking into account (5) and equality of the resistance of the shunt and the input resistance of the bridge circuit, we can derive the dependence of the TCS of the input resistance of the shunted bridge circuit:

The output voltage of the bridge circuit after shunting the input resistance, taking into account dependencies (1) and (5), can be represented as follows:

When exposed to temperature, the output voltage of the sensor after turning on the resistor R _i and a temperature-dependent shunt formed by the series connection of the resistors Rα _in and R _dvh , taking into account (1) (5), (8), can be represented as follows:

As shown in the description of the prototype, TFC can be expressed through the output signals of the sensor:

Substituting (9) and (10) into expression (11), we can obtain the dependence of the DC-link circuit of the bridge circuit:

The nonlinearity of the DC circuit of the bridge circuit will be:

where Δt ⁺ = t ⁺ -t ₀ , Δt ^- = t ^- -t ₀ - positive and negative temperature range;

t ₀ - normal temperature;

t ⁺ , t ^- - upper and lower limit of the operating temperature range;

α ⁺ _to , α ^- _to - TFC of the sensor bridge circuit at t ⁺ and t ^- respectively;

α ⁺ _d , α ^- _d - TFC of strain gauges at temperature t ⁺ and t ^- respectively;

α ⁺ _vhsh , α ^- _vhsh - TCS of the input resistance of the shunted bridge circuit of the sensor at t ⁺ and t ^- respectively;

Δα _to is the nonlinearity of the DC coupler of the bridge circuit.

The prototype allows compensation of the multiplicative temperature error taking into account the non-linearity of the temperature characteristic of the output signal of the sensor, when the non-linearity of the DC-link circuit of the bridge circuit meets the condition Δα _to ≤-2 · 10 ^-6 1 / ° С. For this reason, it is necessary to ensure Δα _to ≤-2 · 10 ^-6 1 / ° C, choosing the TCS of the temperature-dependent shunt, defined by the ratio of the nominal value Rα _in and R _dvh . Thus, to find the required ratio of the resistor values Rα _in and R _dvh , the equation should be solved:

To convert the positive nonlinearity of the DC current factor of the sensor bridge circuit into negative in equation (14), substitute expression (8) and (4), solve the resulting equation with respect to the value of the thermally dependent resistor Rα _in . The value of the resistor R _{dvc is} calculated by the formula:

To determine the area of transformation of the positive nonlinearity of the DC link bridge TTC to negative, it is necessary to solve equation (14) taking into account (8) and (4), with respect to Rα _in , and also calculate the value of the resistor R _dvh according to formula (15) with the following initial data:

1. The input impedance of the bridge circuit: R _I = 1000 Ohm;

2. The nominal value of the thermally dependent shunt: Rα _in + R _dvh = 1000 Ohm;

3. The resistance of the resistor to adjust the sensitivity: R _i = 100 Ohm;

4. TKH strain gages takes values: α _d = (0 ... 10) · 10 ^-4 1 / ° C;

5. the non-linearity of the TFC of the strain gauge takes the values: Δα _d = (0, ... 10) -10 ^-6 1 / ° С;

6. TKS input resistance: α _I = (0 ... 10) · 10 ^-4 1 / ° C;

7. nonlinearity TCR of the input resistance: Δα _in = 5 · 10 ^-6 1 / ° C;

8. TCS of a thermally dependent resistor Rα _in : α _к = 4 · 10 ^-3 1 / ° С;

When evaluating the transform domain positive nonlinearity TCF bridge circuit in the negative considered one of the limiting values of nonlinearity TCR of the input resistance (Δα _in = -5 · 10 ^-6 1 / ° C) as a numerical experiment was conducted previously, which revealed that the effect of nonlinearity TCS of the input resistance to the limiting value of the nonlinearity of the DCS bridge circuit, at which it is possible to convert the positive nonlinearity of the DCS bridge circuit to negative, in the entire range of possible values of TCS input with disobedience and its nonlinearity is small (less than 2%).

The calculation results for Δα _d = (0, 1, 5, 10) · 10 ^-6 1 / ° C are summarized in table 1.

Table 1 The limits of the region of transformation of the positive nonlinearity of the DC circuit of the bridge circuit into negative α _in · 10 ^-4 , 1 / ° С Δα _in · 10 ^-6 , 1 / ° С Δα _d · 10 ^-6 , 1 / ° С α _d · 10 ^-4 , 1 / ° С Rα _in , ohm R _dvh , Ohm 0 -5 0 0,000 80,500 919,500 10,000 295,101 704,899 0 -5 one 0,000 102,849 897,151 10,000 307,444 692,556 0 -5 5 0,000 164,190 835,910 10,000 349,669 650,331 0 -5 10,000 0,000 217,677 782,323 10,000 392,624 607,376 one -5 0,000 0,000 78,624 921,376 10,000 317,181 682,819 one -5 1,000 0,000 101,927 898,073 10,000 328,216 671,784 one -5 5,000 0,000 164,527 835,473 10,000 366,972 633,028 one -5 10,000 0,000 218,535 781,465 10,000 407,463 592,537 5 -5 0,000 2,223 No roots 2,224 47,704 952,296 10,000 362,982 637,018 5 -5 1,000 1,283 No roots 1,284 32,327 967,673 10,000 372,190 627,810 5 -5 5,000 0,000 118,123 881,877 10,000 405,655 594,345 5 -5 10,000 0,000 190,208 809,792 10,000 441,990 558,010 10 -5 0,000 6,507 No roots 6,508 132,873 867,127 10,000 351,817 648,183 10 -5 1,000 6.066 No roots 6,067 121,046 878,954 10,000 362,122 637,878 10 -5 5,000 4,293 No roots 4,294 79,149 920,851 10,000 398,838 601,162 10 -5 10,000 1,916 No roots 1,917 47.315 952,685 10,000 437,792 562,208

Analysis of the results (table 1) allows us to draw the following conclusions:

1. Shunting the bridge circuit with a thermally dependent resistor Rα _in and a thermally independent resistor R _dvh allows you to convert the positive nonlinearity of the DC-link circuit of the sensor to negative in a limited area (Fig. 1, table 2).

2. With an increase in the non-linearity of the TCD strain gages, the area of transformation of the positive non-linearity of the TFC of the bridge circuit to the negative is expanded (Fig. 1).

3. With the increase of the DC coupling factor of the bridge circuit, the scope of the circuit method for converting the positive non-linearity of the DC coupling circuit of the bridge circuit into negative is expanded (Fig. 1).

Based on the results of solving equation (14), we obtained the areas for converting the positive nonlinearity of the DC-link circuit of the bridge circuit into negative, given by Table 2.

table 2 The area of transformation of the positive nonlinearity of the DC circuit of the bridge circuit into negative The non-linearity of the TSC strain gage Δα _d · 10 ^-6 , 1 / ° C

TCS input impedance

The minimum value of the TCC strain gauge αmin · 10 ^-4 , 1 / ° C 0 0,000 ... 10,000 -300.175 · α _in ² + 1.344 · α _in -4.033 · 10 ^-4 one 0,000 ... 10,000 -453.191 · α _in ² + 1.668 · α _in -6.079 · 10 ^-4 2 0,000 ... 10,000 -554.642 · α _in ² + 1.911 · α _in -7.945 · 10 ^-4 3 0,000 ... 10,000 -661.533 · α _in ² + 2.169 · α _in -9.892 · 10 ^-4 four 0,000 ... 10,000 -774.878 · α _in ² + 2.442 · α _in -11.932 · 10 ^-4 5 0,000 ... 10,000 -895.654 · α _in ² + 2.734 · α _in -14.091 · 10 ^-4 6 0,000 ... 10,000 -1011.958 · α _in ² + 3.026 · α _in -16.299 · 10 ^-4 7 0,000 ... 10,000 -1138 · α _in ² + 3.340 · α _in -18.648 · 10 ^-4 8 0,000 ... 10,000 -1261.565 · α _in ² + 3.658 · α _in -21.067 · 10 ^-4 9 0,000 ... 10,000 -1213,603 · α _in ² + 3,669 · α _in -22,140 · 10 ^-4 10 0,000 ... 10,000 -1292.238 · α _in ² + 3.910 · α _in -24.263 · 10 ^-4

To verify the correctness of the proposed solution, we will calculate the compensation elements and the multiplicative sensitivity of the sensor after compensation.

Example

Compensate for the multiplicative temperature error and determine the temperature sensitivities of the sensor with an equal arm bridge measuring circuit at temperatures corresponding to the limits of the operating temperature range, taking into account the following initial data:

- input impedance of the bridge circuit R _I = 1000 Ohm;

- the output resistance of the bridge circuit R _o = 1000 Ohm;

- the resistance of the resistor R _i included in the power circuit: R _i = 100 Ohm.

- TCS of the thermally dependent resistor R _αin and R _αout is α _к = 4 · 10 ^-3 1 / ° С;

- TCS output resistance at temperatures corresponding to the limits of the operating temperature range: α ⁺ _out = 10 ^-3 1 / ° C, α ^- _out = 1,005 · 10 ^-3 1 / ° C;

- TCS input resistance at temperatures corresponding to the limits of the operating temperature range: α ⁺ _bx = 10 ^-3 1 / ° C, α ^- _bx = 1,005 · 10 ^-3 1 / ° C;

- TKH strain gages at temperatures corresponding to the limits of the operating temperature range: α ⁺ _d = 6.06 · 10 ^-3 1 / ° C, α ^- _d = 6 · 10 ^-4 1 / ° C;

;- the total relative change in the resistance of the strain gages at the nominal value of the measured parameter

;

- temperature range of operation of the sensor: 20 ± 100 ° C;

- supply voltage U _pit = 10V.

Since the non-linearity of the DC current factor of the bridge circuit Δα _d = α ⁺ _d -α ^- _d = 6 · 10 ^-6 1 / ° С and the resistance of the power source is negligible, to ensure the negative non-linearity of the DC current factor of the bridge circuit of the sensor, a thermally independent resistor R _i must be included in the power circuit and to shunt the input resistance with a thermally dependent shunt formed by a thermally dependent resistor Rα _in and a thermally independent resistor R _dvh . To verify the applicability of the proposed circuit method, it is necessary to verify the affiliation of the DC link bridge and its nonlinearity of the region specified in table 2. In accordance with table 2 and taking into account the fact that Δα _d = 6 · 10 ^-6 1 / ° C, α ⁺ _out = 10 ^-3 1 / ° С and α ^- _д = 6.0 · 10 ^-4 1 / ° С, the inequality that defines the region of transformation of positive nonlinearity into negative takes the form:

Fulfillment of this inequality allows us to conclude that it is possible to obtain the required negative non-linearity of the DC current factor of the bridge circuit Δα _to ≤-2 · 10 ^-6 1 / ° С, bypassing the input resistance of the sensor bridge circuit with a temperature-dependent shunt. The resistance of the shunt should be taken equal to the input resistance of the bridge circuit of the sensor:

R _αin + R _dvh = R _in = 1000 Ohm.

The input resistance of a shunted bridge circuit, taking into account (5), will be:

.

.

To determine the value of the thermally dependent resistor R _αin included in the shunt, we will solve equation (14) taking into account (4) and (8):

,

,

where in accordance with (4) and (8):

;

;

;

;

.

.

The solution to the equation is the value of the nominal _temperature- dependent resistor R _αin = 247,097 Ohm. The resistance of the thermally independent resistor R _dvh included in the shunt in accordance with (15) will be:

.

.

To determine the DC current of the bridge circuit after turning on the temperature-dependent shunt, the sensor output voltages should be calculated under normal conditions and at temperatures corresponding to the limits of the operating temperature range. Under normal conditions, the output voltage in accordance with (9) will be:

;

;

TCS of a thermally dependent shunt in accordance with (4) will be:

.

.

The TCS of the input resistance of the bridge circuit after turning on the temperature-dependent shunt at temperatures corresponding to the limits of the operating temperature range, in accordance with (8), will be:

;

;

.

.

In this case, the sensor output signals at temperatures corresponding to the limits of the operating temperature range, in accordance with (10), will be:

;

;

.

.

The TCF of the bridge circuit at temperatures corresponding to the limits of the operating temperature range, in accordance with (14), will be:

;

;

.

.

Thus, the nonlinearity of the DC circuit of the bridge circuit will be:

.

.

Check the affiliation of the DC circuit bridge and its non-linearity of the scope of the prototype specified by the system:

Given the resistance values of the output TCR (α ⁺ _O 1 = 10 ^-3 / ° C) TCF bridge circuit (α ⁺ _do = 7.683 · 10 ^-4 1 / ° C) and its nonlinearity (Δα = _d · 10 -2 ^{- 6} 1 / ° С) system (16) will take the form:

The fulfillment of this inequality allows us to conclude that it is possible to make further compensation for the multiplicative temperature error using the prototype. To determine the values of the compensation resistors, you must solve the system of equations:

The solution to this system of equations is the following values of the compensation resistors: R _αout = 405.324Ohm and R _double = 289084.900Ohm. After turning on the resistors R _i , R _αinx , R _dvh , R _αout and R _{two, the} electrical circuit of the sensor will take the form shown in _figure 2.

The resistance of the resistor R _αout , shunted by the resistor R _two , will be:

.

.

In this case, the voltage of the output signal in accordance with the description of the prototype will be:

.

.

At a temperature t ⁺ = 120 ° C, the resistance of the resistor R _αout , shunted by the compensation resistor R _two , will be:

.

.

Thus, the output voltage of the sensor will take the following value:

.

.

At a temperature t ^- = -80 ° C, the resistance of the resistor R _αout , shunted by the compensation element R _two , will be:

.

.

Thus, the output voltage of the sensor will take the following value:

.

.

With the received values of the output voltage of the sensor

the multiplicative sensitivity of the sensor to temperature in accordance with the prototype will be:

;

;

.

.

Thus, the sensitivity obtained after compensation is much less than the maximum permissible temperature sensitivity (S _ktdop = 10 ^-4 1 / ° С).

The proposed method for full compensation of the multiplicative temperature error showed a high accuracy of compensation, which depends only on the accuracy of manufacturing compensation resistors and the accuracy of determining the physical characteristics of strain gauges.

Claims (1)

A method for tuning strain gauge sensors with a bridge measuring circuit by a multiplicative temperature error, taking into account the positive non-linearity of the temperature characteristic of the sensor output signal, namely, when the load resistance R _n > 500 kOhm, the temperature sensitivity coefficient (TCR) of the bridge circuit is determined α ⁺ _to and α ^- _up to a temperature range Δt ⁺ = t ⁺ -t ₀ and Δt ^- = tt _0, where t ₀ ⁺ t, t ^- - normal temperature, the upper and lower limit of the operating temperature range, respectively, calculated nelineynos s TCF bridge circuit _to Δα = α ⁺ _to -α ^- _before, if the nonlinearity TCF bridge circuit takes a negative value, the load resistance R k _n ≤2 determine the output resistance bridge circuit, the output TCR resistance bridge circuit for temperature range ⁺ Δt and Δt ^- , check the presence of the _{DC-link TCD} and the non-linearity of the DC link of the bridge in the field of application and, if the sensor parameters are in the field of application, calculate the value of the resistors R _αout and R _two , set the _temperature- dependent resistor R _αout , shunted termon by an independent resistor R _two , into the output diagonal of the sensor bridge circuit, characterized in that if the non-linearity of the TFC of the bridge circuit takes a positive value, then after determining the non-linearity of the TFC of the bridge circuit and before determining the output resistance of the bridge circuit, as well as the TCS of the output resistance of the bridge circuit, the positive nonlinearity of the DC circuit of the bridge circuit into negative by shunting the input resistance of the bridge circuit with a temperature-dependent shunt, which is formed by sequentially switching on the temperature-dependent of a resistor R _αin and a thermally independent resistor R _dvh , when a thermally independent resistor R _{i is} included in the power circuit, for which, for R _n > 500 kΩ, the DC-to-current ratio of the strain gages α ⁺ _d and α ^- _d for the temperature range Δt ⁺ and Δt ^, respectively, calculate the nonlinearity TCF gages _d Δα = α ⁺ _d -α ^- _d, is determined resistance value R of the input _Rin, TCR of the input resistance _Rin α ^+, α ^- _Rin for temperature range ⁺ Δt and Δt ^- respectively, reveal presence and α ⁺ _d Δα _d in defined by the table
The non-linearity of the TSC strain gage Δα _d · 10 ^-6 , 1 / ° C TCS input impedance $${\alpha }_{\mathrm{at}x}^{+}\cdot \mathrm{one}{0}^{-\mathrm{four}},\mathrm{one}{/}^{\circ }\mathrm{FROM}$$

The minimum value of the TCI of the strain gauge α _dmin · 10 ^-4 , 1 / ° C 0 0,000 ... 10,000 -300.175 · α _in ² + 1.344 · α _in -4.033 · 10 ^-4 one 0,000 ... 10,000 -453.191 · α _in ² + 1.668 · α _in -6.079 · 10 ^-4 2 0,000 ... 10,000 -554.642 · α _in ² + 1.911 · α _in -7.945 · 10 ^-4 3 0,000 ... 10,000 -661.533 · α _in ² + 2.169 · α _in -9.892 · 10 ^-4 four 0,000 ... 10,000 -774.878 · α _in ² + 2.442 · α _in -11.932 · 10 ^-4 5 0,000 ... 10,000 -895.654 · α _in ² + 2.734 · α _in -14.091 · 10 ^-4 6 0,000 ... 10,000 -1011.958 · α _in ² + 3.026 · α _in -16.299 · 10 ^-4 7 0,000 ... 10,000 -1138 · α _in ² + 3.340 · α _in -18.648 · 10 ^-4 8 0,000 ... 10,000 -1261.565 · α _in ² + 3.658 · α _in -21.067 · 10 ^-4 9 0,000 ... 10,000 -1213,603 · α _in ² + 3,669 · α _in -22,140 · 10 ^-4 10 0,000 ... 10,000 -1292.238 · α _in ² + 3.910 · α _in -24.263 · 10 ^-4
if α ⁺ _d and Δα _d satisfy the conditions given in the table, the resistor value R _{i is} equal to 100 Ohms, and the resistance of the shunt formed by the series connection of the resistors R _αin and R _dvh equal to the input resistance of the sensor bridge circuit (R _αin + R _dvh = R _in ), determine the value of the value of the thermally dependent resistor R _αin , solving the following equation with respect to the value of R _αin :
$$\begin{array}{c}\frac{0,5R_{\mathrm{at}x}{\alpha }_d^{+}\left(\mathrm{one}+{\alpha }_{\mathrm{at}xw}^{+}\Delta t^{+}\right)+R_i\left({\alpha }_{\mathrm{at}xw}^{+}+{\alpha }_d^{+}+{\alpha }_{\mathrm{at}xw}^{+}{\alpha }_d^{+}\Delta t^{+}\right)}{0,5R_{\mathrm{at}x}\left(\mathrm{one}+{\alpha }_{\mathrm{at}xw}^{+}\Delta t^{+}\right)+R_i}-\\ -\frac{0,5R_{\mathrm{at}x}{\alpha }_d^{-}\left(\mathrm{one}+{\alpha }_{\mathrm{at}xw}^{-}\Delta t^{-}\right)+R_i\left({\alpha }_{\mathrm{at}xw}^{-}+{\alpha }_d^{-}+{\alpha }_{\mathrm{at}xw}^{-}{\alpha }_d^{-}\Delta t^{-}\right)}{0,5R_{\mathrm{at}x}\left(\mathrm{one}+{\alpha }_{\mathrm{at}xw}^{-}\Delta t^{-}\right)+R_i}=-2\cdot \mathrm{one}{0}^{-6},\end{array}$$

Where $${\alpha }_{\mathrm{at}xw}=\frac{R_{\mathrm{at}x}\left[{\alpha }_w\left(\mathrm{one}+{\alpha }_{\mathrm{at}x}\Delta t\right)+{\alpha }_{\mathrm{at}x}\left(\mathrm{one}+{\alpha }_w\Delta t\right)\right]}{R_{\mathrm{at}x}\left(2+{\alpha }_{\mathrm{at}x}\Delta t+{\alpha }_w\Delta t\right)}$$

- TKS input resistance of the bridge circuit, shunted with resistors R _αin and R _dvh ;
$${\alpha }_w=\frac{R_{\alpha \mathrm{at}x}\cdot {\alpha }_{\mathrm{to}}}{R_{\alpha \mathrm{at}x}+R_{d\mathrm{at}x}}$$

- TCS shunt formed by the series connection of resistors R _αin and R _dvh ;
calculate the value of the thermally independent resistor R _dvh according to the formula:
$$R_{d\mathrm{at}x}=R_{\mathrm{at}x}-R_{\alpha \mathrm{at}x},$$

include a thermally independent resistor R _i in the diagonal of the power supply of the sensor bridge circuit, resistors R _αin and R _dhx connected in series with each other, bypass the input resistance of the bridge circuit, determine the TCD of the sensor bridge circuit and its nonlinearity after turning on the resistors R _αin , R _dvh and R _i .

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