JPH02159521A - Flow velocity meter - Google Patents

Abstract

PURPOSE:To enable precise measurement of a flow velocity even in an electromagnetic field by arranging an electric heat generating body at the tip of a probe provided with an optical fiber so that radiation from the heat generating body is sent to the base end side of the probe through the optical fiber. CONSTITUTION:An electrically heating wire 9 provided at the tip of a probe 6A is connected to the tip of an electric cord 8, a fixed Joule heat (which is deprived by a fluid) is generated by a fixed current supplied from a power source 2 and radiation emitted from the heating wire 9 is sent to a measuring device 3 through an optical fiber 7A. When light is projected to a sensor 10 provided at the tip of a probe 6B from an optical fiber 7B, a return light from the sensor 10 is sent to a measuring device 3 through the optical fiber 7B. The measuring device 3 measures a radiation intensity from a radiant to determine a temperature Tx of the electrically heating wire 9 and a temperature T0 of a fluid is measured from a return light. Thus, when the probes 6A and 6B are inserted into a tube 11 to determine a difference value T0-Tx between the temperatures T0 and Tx by measuring the temperatures, a flow velocity can be determined by computation 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current meter that detects the velocity of a fluid by utilizing the cooling effect of a heating element by the fluid.

[Conventional technology]

An example of this type of anemometer is a thermal anemometer for measuring the wind speed. This microanemometer is equipped with a heating element and a temperature sensor that measures the temperature of the heating element and the air temperature, and controls the heating element to be 10 degrees higher than the air temperature based on the measured value from the temperature sensor. It is. When the wind cools the heating element, heat is generated equal to the amount of heat taken away to maintain a temperature difference of about 10 degrees, and the voltage change that appears on the heating element at this time is used as a wind speed signal.

In this microanemometer, the temperature is measured by passing a current to heat the heating element and measuring the resistance value, or in other words, the voltage value, of the object to be measured, which has the same temperature as the heating element and the air temperature. ing.

Since the current meter exemplified above measures temperature using electrical properties, it is affected by electromagnetic induction noise in an electromagnetic field. For example, equipment that uses high frequencies will be affected by harmonic noise, and if it is buried underground along with high-voltage power lines, it will be affected by electromagnetic field noise. It may also be affected by lightning. Therefore, in an electromagnetic field, the error component included in the measured temperature value increases, making it difficult to accurately measure the flow velocity.

The present invention has been made in view of these circumstances, and its purpose is to enable precise measurement of flow velocity even in an electromagnetic field.

[Means to solve the problem]

In order to achieve the above-mentioned invention, in the current meter according to the first invention, an electric heating element is provided at the tip of a probe equipped with an optical fiber, and radiant light from the heating element passes through the optical fiber to the proximal end of the probe. A current supply means for supplying a predetermined current to the heating element and a measuring means for measuring the intensity of the radiant light sent through the optical fiber are provided.

Moreover, in the current meter according to the second invention, an electric heating element is provided at the tip of the probe equipped with an optical fiber, and the radiant light from the heating element is sent to the proximal end side of the probe through the optical fiber. In addition, a measuring means for measuring the intensity of the radiant light sent through the optical fiber, and a current controlling means for controlling the amount of current supplied to the heating element in order to keep the detected value of the measuring means constant. .

[For production]

(a) According to the first invention, the current supply means supplies a predetermined current to the heating element to generate Joule heat. Since this Joule heat is proportional to the square of the current value, a predetermined amount of heat is always generated from the heating element. Since the generated heat is removed by the fluid, the heating element is cooled and its temperature decreases.

Radiant light is emitted from the heating element, and this radiant light is
The higher the temperature of the heating element, the stronger it becomes, and it is sent to the proximal end through the optical fiber inside the probe. Then, the intensity of the radiant light is measured by the measuring means. Since this measured value and the flow velocity have a negative correlation, the flow velocity can be determined by calculating the intensity of the measured radiation light. Incidentally, the relationship between temperature (T), radiation intensity (E), and wavelength (λ) is shown in FIG.

(b) According to the second invention, the current supply means supplies current to the heating element to generate Joule heat. Since the generated heat is removed by the fluid, the heating element is cooled and its temperature tends to decrease.

The intensity of the radiant light from the heating element is measured by the measuring means in the same way as described above, and when the temperature of the heating element decreases, the current control means functions to keep the measured value constant, and the current is supplied to the heating element. control the amount of current. Since there is a positive correlation between the current value and the flow rate at this time, the flow rate can be determined by calculating the measured current value.

〔Effect of the invention〕

According to the first and second aspects of the invention, the influence of electromagnetic induction noise in an electromagnetic field is reduced, so errors in measurement values are reduced, and it becomes possible to measure flow velocity more precisely.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

What is shown in FIG. 1 is a current meter that detects the velocity of a fluid by utilizing the cooling effect of a heating element by the fluid in a pipe. The main body (1) of this current meter includes a power source (2) as a current supply means, a measuring device (3) as a measuring means for measuring the intensity of radiant light, a calculation device (4), and a display device (5). Two probes (6A) and (6B) are connected to this main body (1) via connectors. One probe (6A) is for flow velocity measurement, and is an optical fiber (6A).
7A) and the electrical cord (8). The other probe (6B) is for temperature measurement, and the optical fiber (7B
) only through. These probes (6A),
(6B) is a flexible one using a resin outer skin.

The power source (2) is a power source for operating the main body (1), and also serves as a current supply means for passing a constant current through the electric cord (8) for heating.

A heating wire (9) as a heating element provided at the tip of the probe (6A) is connected to the tip of the electric cord (8), and Joule heat is generated in proportion to the square of the current supplied from the power source (2). It is designed to be generated from this heating wire (9).

However, since the current value is constant, the amount of heat generated from the heating wire (9) is also maintained constant.

The heating wire (9) is opposed to the tip of an optical fiber (7A), and the radiant light emitted from the heating wire (9) passes through the optical fiber (7A) to the measuring instrument (3) in the main body (1). ).

Also, at the tip of the other probe (6B) is a photoluminescence sensor (10) that measures the temperature of the fluid.
is provided. The optical fiber (7B) is opposed to the sensor (10), and when light is projected from the optical fiber (7B) to the sensor (10), the return light from the sensor (10) passes through the optical fiber (7B) to the main body ( The signal is sent to the measuring device (3) in 1).

The temperature measuring device (3) is equipped with a light emitter, a wavelength demultiplexer, and a light receiver (all not shown), and detects the radiation from the radiant light sent through the optical fiber (7A) for measuring the flow velocity. The intensity is measured, and the temperature (T, ) of the heating wire (9) is determined from this radiation intensity.
The temperature of the fluid (T,
). Specifically, in Fig. 3, when the maximum radiation intensity is P, T1 is used, when the maximum radiation intensity is E2, T2 is used, and when the maximum radiation intensity is E, T3 is used as the measured value. Output.

The heat of the heating wire (9) is constantly removed by the fluid flowing inside the tube. The amount of heat removed (H) is the temperature of the fluid (To
) and flow velocity (v), and generally the following formula holds true.

H= (B J v + C) (T ka To) Here, B
, C are constants that depend on the physical property constants of the fluid, and H is equal to the Joule heat generated from the heating wire (9), and is a constant value under a constant current.

Therefore, two wooden probes (7A) and (7B) are inserted into the pipe (11) to measure the temperature of the fluid (To) and the heating wire (
9) Measure the temperature (TX) and find the difference value (To-T, )
It can be seen that the remaining flow velocity (v) can be calculated by calculating.

In this current meter, when the temperature of the fluid (To) and the temperature (T, ) of the heating wire (9) are output from the temperature measuring device (3), the calculation device (4) performs the above calculation. Then, the flow velocity (v) is determined, and the result is output to the display device (4) for display.

Figure 2 shows that the current meter is connected to a fire hydrant (13
) is inserted into the interior through the water supply channel (14) to investigate the flow velocity of water in the underground pipe (11).

In this current meter, both probes (7A) and (7
8) are collectively covered with a wooden cable (15), and this cable (15) is passed through a pipe-shaped insertion rod (16) and fixed. The hose connection part of the fire hydrant (13) (
A fire hydrant connection fitting (18) is connected to the fire hydrant connection fitting (17), and a pipe-shaped guide rod (19) is connected to the fire hydrant connection fitting (18).
) is inserted. The cable (15) is inserted into the guide rod (19) from the upper opening along with the insertion rod (16), and the heating wire (9) and sensor (10) at the lower end are immersed in the water in the tube (11).

(Another embodiment) As shown in Fig. 4, the main body (1) of the current meter has a built-in control bag f (12) as a current control means.This control device (12) has a heating wire ( The value of the current flowing through the heating wire (9) is controlled so that the difference value (To T) between the temperature (TX) of the heating wire (9) and the temperature (To) of the fluid is constant.

In other words, by controlling the amount of heat (11), the difference value (To-T,
) is always constant.

The amount of heat (I) is proportional to the square of the current value flowing from the power source. Therefore, it can be seen that by measuring the current value and using the above formula, the remaining flow velocity (v) can be calculated.

In this current meter, when the current value is obtained from the control device (12), the arithmetic device (4) performs the above calculation to obtain the flow velocity (v), and outputs the result to the display device (5). It is displayed as follows.

Note that in carrying out the present invention, when measuring a fluid whose temperature changes, the temperature of the fluid may be separately measured and the measured value may be used to determine the flow velocity. Of course, the temperature detection means can be omitted when measuring a fluid in which there is no temperature change or a slight temperature change. Furthermore, as in the above embodiment (when temperature is measured simultaneously), the measuring means can be changed in various ways.

It should be noted that although reference numerals are written in the claims section for convenience of reference to the drawings, it is clear from this entry that the present invention is not limited to the structure of the attached drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of the current meter according to the present invention, with Fig. 1 showing a schematic configuration, Fig. 2 showing a specific usage state, and Fig. 3 showing the relationship between wavelength, radiation intensity, and temperature. FIG. 4 is a diagram showing a schematic configuration of another embodiment. (2)... Current supply means, (3)...
Temperature measuring means, (6A)... Probe, (7A
)...Optical fiber (8)...Electrical cord, (9)...Heating element, (12)...
・Current control means.

Claims (1)

[Claims] 1. An electric heating element (9) is provided at the tip of a probe (6A) equipped with an optical fiber (7A), and the heating element (9)
current supply means (2) for supplying a predetermined current to the heating element (9) so that the radiated light from the probe (6A) is sent to the proximal end side of the probe (6A) through the optical fiber (7A); A current meter equipped with a measuring means (3) for measuring the intensity of radiant light sent through an optical fiber (7A). 2. An electric heating element (9) is provided at the tip of the probe (6A) equipped with an optical fiber (7A), and the heating element (9)
measurement means (3) for transmitting the radiant light from the optical fiber (7A) to the proximal end side of the probe (6A) and for measuring the intensity of the radiant light transmitted through the optical fiber (7A); 2. The current meter according to claim 1, further comprising current control means (12) for controlling the amount of current supplied to said heating element (9) in order to keep the detected value of said measuring means (3) constant.