JP2003021550A - Temperature compensation device of torque tube type meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure accurately a temperature in the vicinity of a torque tube. SOLUTION: This temperature compensation device is equipped with a first temperature sensor for measuring the temperature in the vicinity of the torque tube, a second temperature sensor for measuring an environmental temperature of a gauge part, a temperature presuming part which obtains a value having a linear relation by calculation from a first temperature T1 measured with the first sensor and a second temperature T2 measured with the second sensor, and sets a presumed temperature by adding an environmental constant to the linear relation, and a measuring part for obtaining a measured value by temperature compensation of a detected output of an angle sensor which is based on the presumed temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensation device for a torque tube type measuring instrument.

[0002]

2. Description of the Related Art FIG. 6 is a front view showing a usage state of a torque tube type level gauge, which is one of torque tube type gauges to which an angle sensor is applied, in which a part of a storage tank is cut away, and FIG. 7 is a float. And FIG. 8 is a front view showing the relationship between the torque arm and the torque arm, and FIG. In the figure, 101 is a storage tank for storing a process fluid, 1
Reference numeral 02 is a guide pipe that is vertically inserted into the storage tank 101 and has its upper portion exposed to the outside. Reference numeral 103 is a float. It is a hanging rod which is hung on the hook to hang the float 103. The torque arm 106 is provided with a V-shaped notch 106a provided on the other end side on the knife edge 107, and a support 110 for attaching one end of the torque tube 109 is attached to the other end side of the torque arm 106.

The torque tube 109 is inserted into the center hole 111a of the torque tube housing 111, and the other end side is attached to the torque tube housing 111 by a mounting screw 112. Reference numeral 113 denotes a torque rod in which one end side is attached to the support body 110 and the other end side is attached with an angle sensor 114 so as to pass through the torque tube 109 and rotate integrally with the torque tube 109.
Is a measuring unit that processes the detection signal of the angle sensor 114 and outputs a measured value, and 116 is a temperature sensor that detects the temperature near the torque tube 109.

FIG. 9 is a vertical sectional view showing the structure of the angle sensor 114, and FIG. 10 is a horizontal sectional view taken along the line aa in FIG. In the figure, 121 is a yoke having a U-shaped cross section attached to the tip of the torque rod 113, 122a and 122b are magnets provided axially symmetrically on the inner surface of the yoke 121, and 123 is located on the line connecting the magnets 122a and 122b. The magnetoelectric conversion element (for example,
Magnetoresistive element, Hall element). The magnetoelectric conversion element 123 includes four magnetoelectric conversion elements 123a, 123b, 12
3c and 123d are sequentially arranged in a plane by changing the arrangement angle by 90 ° and are bridge-connected, and a magnetic field acts in the direction of the terminals O1 and O3 to take out an output from between the terminals O2 and O4.

Therefore, when the torque rod rotates in accordance with the twist angle difference of the torque tube 109 acting on the torque rod 113 and the positions of the magnets 122a and 122b move to the two-dot chain line position in FIG.
The direction of the magnetic field acting on 3a, 123b, 123c, 123d changes. As a result, the output taken out between the terminals O2 and O4 changes, and the liquid level T can be known. FIG. 11 is a block diagram showing a measuring circuit including the angle sensor 114.
5. It has an output circuit 126 having an amplification function. The measurement unit 115 includes an A / D conversion unit 115a and a CPU as a calculation unit.
115b and the D / A conversion part 115c.

Next, the operation will be described. Storage tank 101
The buoyancy generated in proportion to the liquid level T inside the float 103
Is converted into torque by the torque arm 106 and the knife edge 108, on which the torque tube 1 is suspended.
09 is transmitted. The torque tube 109 functions as a process fluid enclosing and torsion spring, and converts torque into an angle. This angle is transmitted to and detected by the angle sensor 114 by the torque rod 113, and based on the detection signal output from the output circuit 125, the measuring unit 11
At 5, the measured value is calculated and output.

In this torque tube type level gauge, the temperature characteristic of the torque tube 109 is a problem.
Metal is usually used for the material of the torque tube,
Metal has a large transverse elasticity coefficient, which results in a fluid temperature characteristic as a direct measuring instrument. As one of the measures,
The sheath thermocouple 116 provided on the measurement unit 115 side is extended in parallel with the torque rod 113 so that the tip of the sheath thermocouple is
A conventional method is to position the torque tube housing 111 near the torque tube mounting portion, measure the temperature near the torque tube with a sheath thermocouple 116, and use the measured value to perform temperature compensation of the detection signal of the angle sensor 114. Came.

[0008]

Since the temperature compensation of the conventional torque tube type measuring instrument is configured as described above, the temperature detecting section tends to be structurally long due to the use of the torque tube. , It is easy to make a temperature gradient in that part. Further, since the torque tube also serves as a seal for the process, it is difficult to perform processing for installing a temperature sensor that directly measures the temperature of the process. For these reasons, there are the following problems. Temperature sensor 1 depending on the difference between process temperature and ambient temperature
A temperature gradient is created at the position where 16 is installed. As a result, the temperature of the torque tube 109 cannot be measured with sufficient accuracy, and even if the temperature compensation is performed, the measured temperature error component appears as a temperature characteristic. Since the temperature gradient that occurs in the vicinity of the temperature sensor differs depending on the fluid substance and pressure in the process, the temperature characteristics of the measuring instrument vary from application to application.

For example, process fluid: oil, process pressure: normal pressure, measured in thermal equilibrium, process temperature Tp = 150.8 ° C, torque tube temperature Ttq = 112.4 ° C, thermocouple measurement temperature Ttc = 74.6 ° C. When the ambient temperature Tat = 12.2 ° C., when the temperature is compensated by the thermocouple measurement temperature Ttc (74.6 ° C.), the torque tube temperature Ttq (112.4).
Temperature characteristic of about 38 ° C. is generated.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a temperature compensating device for a torque tube type measuring instrument capable of accurately compensating the temperature of a torque tube.

[0011]

SUMMARY OF THE INVENTION A temperature compensating device for a torque tube type measuring instrument according to the present invention is a torque tube having one end attached to a housing and the other end being twisted by a rotational force due to a change in a measured value, and the torque tube. A torque rod that passes through the inside of the torque tube and rotates by receiving a rotational force from the other end of the torque tube; an angle sensor attached to the tip of the torque rod to detect the rotation of the torque rod as an angle; Temperature sensor for measuring the temperature of the first temperature sensor, a second temperature sensor for measuring the ambient temperature, a first temperature T1 measured by the first temperature sensor and a second temperature sensor measured by the second temperature sensor. And a temperature estimator that obtains a torque tube estimated temperature by adding an environmental constant to this linear relationship by calculation. It is obtained by a measurement unit for obtaining a measurement value after the temperature compensation of the detection output of the angle sensor on the basis of the estimated temperature.

In the temperature compensating device for a torque tube type measuring instrument according to the present invention, the angle sensor includes a yoke attached to the tip of the torque rod, a magnet axially symmetrically attached to the inner surface of the yoke, and a magnetic force line action of the magnet. And a magnetoelectric conversion element provided on the support so as to be located at a position, obtain the total resistance of this angle sensor, and use the temperature estimated based on this total resistance as the measured temperature of the second temperature sensor. is there.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. Embodiment 1. 1 is a vertical cross-sectional view showing a main part of a torque tube type level gauge which is one of the torque tube type measuring meters according to Embodiment 1 of the present invention. In the figure, a torque tube 9 is inserted into a center hole 11a of a torque tube housing 11, one end side is attached to a torque arm 6 through a support body 10, and the other end side is attached with a mounting screw 12
Is attached to the torque tube housing 11. Reference numeral 13 denotes a torque rod in which one end side is attached to the support body 10 so as to rotate integrally with the torque tube 9 and an angle sensor 14 is attached to the other end side, 15 is a measuring portion, and 16 is a torque. A first temperature sensor 17 measures the temperature near the tube, and a second temperature sensor 17 measures the ambient temperature of the measuring unit 15. FIG. 2 is a block diagram showing a measuring circuit including the angle sensor 14, and the angle sensor 14 includes four magnetoelectric conversion elements 14a and 14a.
b, 14c and 14d are bridge-connected, a voltage is applied between the terminals O1 and O3 by the power supply 18, and a detection signal is output from the output circuit 19 connected between the terminals O2 and O4. The measurement unit 15 has an A / D conversion unit 15a, a CPU 15b as a calculation unit, and a D / A conversion unit 15c. 20
Is a temperature estimator, and has a value that has a linear relationship with two temperature inputs of a first temperature T1 measured by the first temperature sensor 16 and a second temperature T2 measured by the second temperature sensor 17. The value β determined by calculation and determined by the user's application, such as the fluid substance and pressure of the process, in this linear relationship (herein referred to as the environmental constant)
Is added to estimate the temperature of the torque tube 9.

Next, the operation will be described. The operation until the change in the buoyancy acting on the float is converted into the rotation angle of the torque rod 13 is the same as that of the conventional apparatus shown in FIGS. Hereinafter, temperature compensation of the detection signal of the angle sensor 14 will be described. Temperature estimation unit 20
Is the temperature Ttc in the vicinity of the torque tube measured by the first temperature sensor 16, the ambient temperature Trt measured by the second temperature sensor 17, and the environmental constant β, and the following two equations are calculated. A value Ttq having a linear relationship with the temperature is calculated, and this value is output as the torque tube estimated temperature Ttq.

The following method is available as an example of calculating the estimated torque tube temperature Ttq. Ttq = β (Ttc−Trt) + Trt = β · Ttc +
(1-β) Trt Here, the user can freely set the environment constant β by using, for example, a handy communicator or the like according to the application actually using the measuring instrument.

For example, as shown in FIG. 3, the temperature Ttc = 7 near the torque tube measured by the first temperature sensor 16.
When the ambient temperature Trt of the measuring unit measured by the second temperature sensor 17 is 5 ° C. and Trt = 25 ° C., the environmental constant β = 1.
When 5, is set, the estimated torque tube temperature Ttq calculated from the above formula is located on an extension of the linear relationship with respect to the two temperature inputs, and in the illustrated example, the estimated torque tube temperature Ttq = 100 ° C. Then, the output signal of the temperature estimation unit 20 based on this estimated temperature is input to the CPU 15b via the A / D conversion unit 15a together with the detection signal from the angle sensor 14 to detect the temperature of the detection signal from the angle sensor 14. By performing compensation, the measured value can be accurately calculated. And
The obtained measured value is output to, for example, the display unit via the D / A conversion unit 15c.

The environmental constant β is, for example, calculated from experimental data, that the process fluid is steam (pressure 6 Kgf / cm ² ): 1.15, the process fluid is oil: 1.4, and the process fluid is liquid nitrogen: 1. .

As described above, according to the first embodiment, a linear relationship is obtained for temperature inputs from two temperature sensors that detect temperatures at different positions, an environmental constant is added to this linear relationship, and torque is added. Since the estimated tube temperature Ttq is determined, even if the first temperature sensor 16 is arranged at a position distant from the torque tube, the temperature of the torque tube can be accurately estimated, and the temperature with respect to the detection output of the angle sensor 14 can be measured. It is possible to perform accurate compensation and improve the accuracy of the measuring instrument.

Embodiment 2. In the first embodiment, an independent temperature sensor is used as the second temperature sensor 17 that measures the ambient temperature of the measuring unit 15, but in the second embodiment, the total resistance of the angle sensor 14 is used to measure the temperature of the measuring unit. The ambient temperature is estimated.

FIG. 4 is a block diagram showing a measuring circuit according to the second embodiment. The same parts as those in FIG. 2 are designated by the same reference numerals and their duplicate description will be omitted. In FIG. 4, reference numeral 21 denotes a total resistance detection unit for detecting the total resistance R of the angle sensor 14, 22
Is a temperature output unit for outputting the temperature corresponding to the total resistance R, 23
Is a constant current feedback resistor connected between the terminal O3 and the ground, and 24 is a constant current feeding comparator for supplying a constant current to the bridge circuit of the magnetoelectric conversion elements 14a to 14d. The total resistance detection unit 21 and the temperature output unit 22 function as the temperature sensor 17 in the first embodiment.

The temperature output unit 22 has a database that stores the relationship between the total resistance and the temperature obtained in advance by experiments, for example, and reads the temperature for the input total resistance from the database and outputs it. Further, the angle sensor 14 of the illustrated example is one in which four magnetoelectric conversion elements are bridge-connected, but even in the case where two magnetoelectric conversion elements are half-bridge connected, by detecting the total resistance, It can be applied. Since the magnetoelectric conversion elements 14a to 14d, which are the constituent elements of the angle sensor 14, have large temperature characteristics, if the resistance r of the constant current feedback resistor 23 is made extremely small as compared with the total resistance R of the magnetoelectric conversion elements 14a to 14d. , R + r can be detected to detect the temperature. That is, the relationship between the angle sensor output VS and the total resistance R is measured and related within the operating temperature range.
When a constant current i is passed through the magnetoelectric conversion elements 14a to 14d to measure the voltage V across the magnetoelectric conversion elements, the total resistance R of the magnetoelectric conversion elements 14a to 14d is R = V / i. FIG. 5 shows the output voltage V of the entire magnetoelectric conversion element on the vertical axis, but since the current i is constant, it is proportional to the total resistance R of the magnetic conversion elements 14a to 14d. You can know the temperature.

As described above, according to the second embodiment, the ambient temperature of the measuring instrument is obtained from the total resistance R of the angle sensor, that is, the magnetoelectric conversion elements 14a to 14d, and this temperature is determined by the second embodiment. By utilizing the temperature detected by the temperature sensor, the second temperature sensor does not need to be specially provided, and the number of parts used can be reduced, so that the configuration and workability can be simplified and the cost can be reduced.

[0023]

As described above, according to the present invention, a linear relationship is obtained for temperature inputs from two temperature sensors that detect temperatures at different positions, and an environmental constant is added to this linear relationship to obtain a torque. Since it is configured to determine the tube estimated temperature, the temperature of the torque tube can be accurately estimated even if the first temperature sensor is arranged at a position distant from the torque tube, and temperature compensation for the measured value can be performed. It can be performed accurately and the accuracy as a measuring instrument can be improved.

According to the present invention, since the total resistance of the angle sensor is obtained and the ambient temperature of the measuring instrument is estimated from the total resistance, it is necessary to specially provide a temperature sensor for detecting the ambient temperature. But by reducing the parts used,
The configuration and workability can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part of a torque tube type liquid level gauge, which is one of the torque tube type measuring meters in a first embodiment.

FIG. 2 is a block diagram of a measurement circuit according to the first embodiment.

FIG. 3 is an explanatory diagram showing a linear relationship with respect to two temperature inputs.

FIG. 4 is a block diagram of a measurement circuit according to the second embodiment.

FIG. 5 is a relationship diagram between temperature and total resistance.

FIG. 6 is a front view showing a usage state of the torque tube type liquid level gauge with a part of a storage tank cut away.

FIG. 7 is a front view showing a relationship between a float and a torque arm.

FIG. 8 is a vertical cross-sectional view showing a main part of a torque tube type liquid level gauge.

FIG. 9 is a vertical sectional view showing a configuration of an angle sensor.

10 is a cross section taken along line aa of FIG.

FIG. 11 is a block diagram of a measurement circuit in a conventional device.

[Explanation of symbols]

9 Torque tube 11 Torque tube housing 13 Torque rod 14 Angle sensor 15 Instrument part 16 First temperature sensor 17 Second temperature sensor 20 Temperature estimation unit 21 Total resistance detector 22 Temperature output section

Continued front page    F term (reference) 2F013 BC04 BG01 CA01 CB04                 2F056 JG03                 2F063 AA34 AA35 BA30 CB01 DA01                       DB07 DD05 JA09 KA01 KA06                       LA11 LA19 LA20 LA27                 2F069 AA83 AA88 AA99 EE02 EE22                       GG04 GG06 GG16 GG65 HH09                       JJ17 JJ25 KK05 MM04 NN08                       QQ05

Claims (2)

[Claims] 1. A torque tube which has one end attached to a housing and which is twisted by receiving a rotational force due to a change in measured value at the other end, and a torque tube which penetrates through the torque tube and receives a rotational force from the other end of the torque tube to rotate. Torque rod, an angle sensor attached to the tip of the torque rod for detecting the rotation of the torque rod as an angle, a first temperature sensor for measuring a temperature near the torque tube, and a second temperature sensor for measuring an ambient temperature. Temperature sensor, and the first
Of the first temperature T1 measured by the temperature sensor of
A value having a linear relationship with the second temperature T2 measured by the temperature sensor is calculated, and an environmental constant is added to the linear relationship to obtain an estimated temperature of the torque tube, and a temperature estimator based on the estimated temperature. A temperature-compensating device for a torque tube type measuring instrument, comprising: a measuring unit for compensating the temperature detected by an angle sensor to obtain a measured value. 2. The angle sensor comprises a yoke attached to a tip of a torque rod, a magnet axially symmetrically attached to an inner surface of the yoke, and a magnetoelectric conversion device provided on a support so as to be located at a magnetic force line acting position of the magnet. The torque tube type measuring instrument according to claim 1, further comprising an element, wherein the total resistance of this angle sensor is obtained, and the temperature estimated based on this total resistance is used as the measurement temperature of the second temperature sensor. Temperature compensation device.