JPH04297815A - Acoustic conduit length meter - Google Patents

Abstract

PURPOSE:To measure the length of conduit accurately regardless of the type or temperature of gas passing through the conduit. CONSTITUTION:A conduit length meter measures the length of a tubular member 28 by transmitting a pulse sound from a speaker 25 disposed at one end of the tubular member 28, receiving the pulse sound reflected on the other end thereof by means of a microphone 26 and then executing an operation based on the relationship between the propagation time and the sound speed. Sound speed data at a reference temperature are stored for various type of gases passing through the tubular member 28. On the other hand, temperature of gas in the tubular member 28 is detected and the sound speed at the temperature of measuring time is operated using sound speed data corresponding to the type of gas and then the length of the tubular member 28 is calculated based on thus operated sound speed and propagation time.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic pipe length measuring device that uses sound waves to measure the length of pipes.

0002

2. Description of the Related Art Gas pipes, signal cable piping, and the like are buried underground and used for long periods of time.

Taking gas pipes as an example, a gas pipe buried underground consists of a main branch pipe and a service pipe that branches from the main branch pipe to each home or business. A gas meter is connected to the section and is exposed above the ground.

FIG. 4 is a diagram showing the positional relationship between the main branch pipe, the service pipe, and the gas meter.

[0005] In a part A where the gas pipe is buried underground (for example, under a road), a service pipe 2a branches from the main branch pipe 1, and the service pipe 2a is bent at several places by elbows 3, etc. . An elbow is a joint pipe that connects service pipes at a certain angle, and is a pipe with a small radius of curvature. A gas meter 4 is connected to the service pipes 2b and 2c at the part B where the gas pipe is exposed above the ground.For example, the gas meter 4 is fixed to the outer wall of a building (not shown), and the service pipe 2d is connected to the outside wall of the building (not shown). Piped inside.

[0006] When a gas pipe buried underground corrodes or breaks, it is necessary to repair or replace the part, but in that case, the underground pipe is exposed by digging the ground. There are two methods: one is to repair the pipe by digging the ground, and the other is the non-excavation inner surface repair method, which repairs the service pipe without digging into the ground. The non-excavation inner surface repair method is a method in which resin in a fluid state is poured from the outside into the service pipe that requires repair, and then vacuumed and cured to coat the inner surface of the service pipe with resin. Its development is urgent because it is advantageous in terms of cost and security. However, with this construction method, if too much resin is poured in from the outside, the service pipes will become clogged with resin, and conversely, if there is too little resin, the pipes will become clogged with resin.
This results in insufficient timing. Therefore, in this non-excavation inner surface repair method, in order to measure the amount of resin poured into the pipe, it is necessary to calculate the volume inside the pipe in advance, and since the inner diameter of the service pipe is known, the total length of the service pipe is measured. It is necessary to do so.

[0007] Conventionally, as a technique for measuring the length of a service pipe, a method using sound waves is known as shown below (Acoustical Society of Japan Lecture Papers, March 1990).

(1) Long tube measurement system As shown in FIG. 5, one speaker 6 and two microphones 7 and 8 are attached to one end of the long tube 5, and the speaker 6 is equipped with an oscillator. 9 is connected, and an oscilloscope 10 is connected to microphones 7 and 8. This system receives pulsed sound waves emitted from a speaker 6 with two microphones 7 and 8, observes the waveform of the sound waves with an oscilloscope 10, calculates the speed of sound, and calculates the speed of the sound waves at the front end of a long tube 5. The length of the long tube 5 is measured by determining the propagation time from the end 5a to the terminal end 5b.

(2) P. E. Pipe length measuring system As shown in Figure 6, a hose-shaped P. E. A speaker 12 is attached to one end of a (polyethylene) tube 11, and a microphone 13 is attached to the other end. A speaker 12 and a microphone 13 are connected to a measuring device 14. This system measures the length of the tube 11 from the time taken from when a pulsed sound wave of several kHz is emitted from a speaker 12 until it is received by a microphone 13 and from the speed of sound. Although the speaker 12 and microphone 13 are both separated from the tube 11 in the figure, they are actually in close contact with each other.

0010

[Problem to be Solved by the Invention] Generally, when measuring the length of a sealed pipe using sound waves, the speed of sound waves transmitted inside the pipe varies depending on the type, composition, and temperature of the gas inside the pipe. Measuring instruments such as systems (1) and (2), which measure the length of the pipe based on the time it takes from sending sound waves into the pipe until they are reflected back, change the propagation time of the sound waves, so the length of the pipe is measured. The measured value of path length varies depending on the conditions.

The present invention has been made in view of the above points, and its object is to accurately measure the length of a tube without being affected by the type or temperature of the gas inside the tube.

0012

[Means for Solving the Problems] According to the present invention, the above-mentioned object is to provide a sounding means for transmitting a pulsed sound wave from one end of the tubular member into the tubular member, and a sound generating means for transmitting a pulsed sound wave from one end of the tubular member to the other end of the tubular member. sound collecting means for collecting the pulsed sound waves; temperature detection means for detecting the temperature inside the tubular member; storage means for storing the sound velocity value at a reference temperature of the gas existing within the tubular member; The acoustic conduit is controlled by a control means that measures the length of the tubular member from the time from when the sound wave is sent until it is collected, the temperature, and the sound velocity value inside the tubular member determined from the sound velocity value at the reference temperature. A length measuring device was constructed.

[0013]

[Operation] In the acoustic pipe length measuring device of the present invention, a pulsed sound wave sent out from one end of the tubular member by the sounding means is reflected at the other end of the tubular member, and the sound is collected by the sound collecting means at one end of the tubular member. At the same time, the temperature within the tubular member is detected by the temperature detection means, the sound speed of the gas inside the pipe is calculated from the detected temperature, and the time and sound speed obtained by timing are calculated. is configured to measure the length of the tube from.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the drawings.

FIG. 1 shows a schematic configuration of an embodiment of a pipe length measuring device according to the present invention.

As shown in the figure, the pipe length measuring device includes a coupling member 16, amplifiers 17 and 18, a D/A converter 19, and an A/A converter 19.
D converter 20, temperature sensor drive circuit 21, CPU 22,
It is composed of a display 23, a switch S, and a memory 24. The coupling member 16 is made of a cylindrical member made of metal, for example, and can be detachably attached to the supply pipe 28 through a thread groove 16a formed inside one end of the coupling member 16. A speaker 25 and a microphone 26 are connected to the other end of the coupling member 16.
A temperature sensor 27 for measuring the temperature inside the tube is fixed near the other end through the tube wall, and the tip thereof is exposed inside the tube. This coupling member 16 is formed so that when attached to the internal tube 28, one end of the internal tube 28 is in a sealed state. Note that the temperature sensor 27 and the temperature sensor drive circuit 21 constitute a temperature detection means.

The speaker 25 sends pulsed sound waves into the internal tube 28 based on a command from the CPU 22, and the microphone 26 collects the reflected sound from the internal tube 28.
The output signal is amplified by amplifier 18.

A/D converter 20 converts the analog signal from amplifier 18 into a digital signal.

The temperature sensor 27 is composed of, for example, a thermistor, and detects the temperature inside the supply pipe 28 by converting it into a resistance value, but is not limited to this, and a thermocouple may also be used.

The temperature sensor drive circuit 21 is a temperature sensor 27
Converts resistance changes into voltage changes.

The memory 24 stores information about the type of gas (
For example, data on the relationship between natural gas, propane gas) and the sound velocity value at a reference temperature (for example, 0°C) are stored, and the operator can select the sound velocity data corresponding to the type of gas. Since this is done by switching the switch S, the pipe length can be measured even for different gases. Note that the type of gas in the service pipe 28 is determined using a gas sensor (not shown), and the sound speed data corresponding to the type of gas is determined.
The data may also be read out.

The display 23 is for displaying the length of the service pipe 28 measured by this measuring device, and may be a liquid crystal display or an LED (light emitting diode).

The CPU 22 is composed of, for example, a microprocessor, and is connected to the D/A converter 19, the A/D converter 20, the display 23, and the switch S. The CPU 22 instructs the D/A converter 19 to generate a pulsed sound wave, receives the reflected wave of the pulsed sound wave collected by the microphone 26 from the A/D converter 20, transmits the sound wave, and then collects the sound wave. In addition to measuring the time until the sound is heard, a signal of the temperature inside the service pipe 28 is received from the temperature sensor drive circuit 21, and the sound velocity value at the reference temperature read from the memory 24 for the type of gas inside the service pipe 28 is measured. The speed of sound is calculated based on the data. The CPU 22 calculates the length of the service pipe 28 from the calculated sound speed and the above-mentioned time, and displays the calculated value on the display 23.

Next, the operation of the pipe length measuring device will be explained with reference to FIGS. 2 and 3.

FIGS. 2 and 3 are flowcharts for explaining the operation of the acoustic pipe length measuring device.

In FIG. 2, when measurement of the pipe length of the service pipe 28 is started, the CPU 22 initializes each parameter and declares an array "DATA (4000)". Note that "DATA (4000)" is an array with a number of 4000 pieces, and this is an array in which the values obtained by sampling the sound wave signals collected and output by the microphone 26 at time intervals of Δt (s) are arranged in the order of time. It is something (S-1)
.

0 is assigned to a variable N representing the number of repetitions of the operation (S-2), and 0 is assigned to DATA (*). This represents setting all elements of the array DATA (4000) to 0 (S-3).

An analog signal for generating pulsed sound waves is output from the D/A converter 19 to the amplifier 17 (S
-4). As a result, a pulsed sound wave is generated from the speaker 25 in the service pipe 28 for one cycle.

Assign 0 to the variable t representing the number of arrays (
S-5), the output “da” of the amplifier 18 is sent to the A/D converter 20.
ta' is taken in (S-6). This is microphone 2
The signal of the reflected wave of the pulsed sound wave received at 6 (output “dat
a'') is captured at every sampling time Δt. The value of DATA(t)+data is assigned to each element DATA(t) of the array "DATA(4000)" (S-6). The value of this data is the output value of the amplifier 18 at the variable t, and the element DATA(t) of each array
are assigned to each. Assign variable t+1 to variable t (
S-8), determine whether the value of variable t is less than 4000, and if it is less than 4000, return to step (S-6) (
S-9). This allows data for one cycle of the pulsed sound wave to be
data is sampled. The value N+1 is assigned to the variable N (S-10), and the process proceeds to the next step (S-11).

In FIG. 3, it is determined whether the value of variable N is less than 100, and if the value of variable N is less than 100, the calculations from step (S-4) to step (S-10) are repeated ( S-11). This is to remove noise by averaging 100 times of data.
N represents the number of additions. Incidentally, if the averaging is performed 100 times, the noise intensity will be reduced to the square root of 1/100, that is, to 1/10. In addition, the number of times N
The value of is not limited to 100.

If the variable N is 100 or more in step (S-11), the A/D converter 20 reads the output voltage of the temperature sensor 27 (S-12).

[0032] The CPU 22 has 4000 array elements DAT.
The value of t whose absolute value is the maximum is selected from A(t) (S-13). This is because the amplitude of the reflected wave at the open end of the service tube 28 becomes maximum, and that maximum value is utilized. The reason why the maximum value is taken here is that the waveform of the reflected wave is theoretically symmetrical with its positive and negative components, so there are two maximum values, but in reality there are two maximum values. When a sound wave is output from the speaker 25, one side of the vibrating surface of the speaker 25 vibrates weakly due to inertia, for example, the surface corresponding to the positive component, and the surface corresponding to the negative component vibrates strongly, resulting in reflected waves. It has an asymmetrical shape. As a result, the peak value of the amplitude of the negative component (second) is selected.

The sound velocity value vo (m/s) at 0°C of the gas inside the service tube 28 is read out from the memory 22 (S-
14). In addition, as mentioned above, by changing the switch S by the measuring person, the 0 corresponding to the type of gas in the service pipe 28 is
The sound velocity value in °C is obtained.

Using the temperature T (°C) inside the service tube 28 obtained by the temperature sensor 27 and the temperature sensor drive circuit 21, the current sound velocity v (m/m/ s
) is calculated (S-15),

[0035]

[Equation 1] v=vo{1+T/273}1/2 Next, calculate the pipe length L (m) of the service pipe 28 using the following equation 2 (S
-16).

[0036]

[Equation 2] L=v・t・Δt/2 The value of the pipe length L of the service pipe 28 calculated in this way is displayed on the display 2.
3 (S-17).

As described in detail above, according to this embodiment, the temperature of the gas in the service pipe 28 is detected, the detected temperature is used to calculate the sound velocity value at that temperature, and the calculated value is Since the length of the service pipe 28 is calculated using the sound velocity value, the length of the service pipe 28 can be accurately measured regardless of the temperature or type of gas in the service pipe 28.

[0038]

As explained above, in the present invention, the sound velocity value at the reference temperature of the gas existing inside the tubular member is stored, and the temperature inside the tubular member is detected by a pipe length measuring device. The time and temperature from when a pulsed sound wave is sent out to when it is collected, as well as the sound velocity value at this measured temperature, are calculated, and this sound velocity value is used to measure the pipe length of the tubular member. The length of the tubular member can be accurately measured regardless of the type of gas inside the tubular member or the environmental temperature.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an acoustic pipe length measuring device according to the present invention.

FIG. 2 is a flowchart for explaining the operation of the pipe length measuring device shown in FIG. 1;

[Fig. 3] Flow continuing from the flowchart shown in Fig. 2.
It is a chart.

FIG. 4 is a diagram showing the positional relationship between a gas pipe and a gas meter.

FIG. 5 is a diagram showing an example of a conventional pipe length measurement system.

FIG. 6 is a diagram showing another example of a conventional pipe length measurement system.

[Explanation of symbols]

16 Connecting member 17,18 Amplifier 19 D/A converter 20 A/D converter 21 Temperature sensor drive circuit 22 CPU 23 Display 24 Memory 25 Speaker 26 Microphone 27 Temperature sensor

Claims (1)

[Claims] 1. Sound generating means for transmitting pulsed sound waves into the tubular member from one end of the tubular member, and a sound collector for collecting the pulsed sound waves reflected at the other end of the tubular member at one end of the tubular member. sound means; temperature detection means for detecting the temperature within the tubular member; storage means for storing a sound velocity value at a reference temperature of the gas existing within the tubular member; It is characterized by comprising a control means for measuring the pipe length of the tubular member from the time until the sound is heard and the sound velocity value inside the tubular member determined from the sound velocity value at the temperature and the reference temperature. Acoustic pipe length measuring device.