JPH02280011A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To measure many kinds of fluid such as gas and liquid, etc., by means of one sensor by providing a frequency multiplication circuit in the path of a signal inputted in the phase comparator of an ultrasonic sensor. CONSTITUTION:The frequency multipliers 10 are respectively provided in the paths where an oscillation signal S1 and a reception signal S2 are supplied to the phase comparator 6 and the original signals S1 and S2 or frequency multiplication signals S1' and S2' are supplied to the phase comparator 6 by a changeover switch 11. With such constitution, ultrasonic wave with low frequency is used in the fluid which is difficult to transmit and propagate the ultrasonic wave, such as the gas, etc., and the signal is compared in terms of phase after performing frequency multiplication processing, so that a flow is detected surely enough to calculate a phase modulation quantity even under the condition of the fluid that phase modulation becomes very small. Then, in the case of the liquid, the changeover switch 11 is switched and the original signals S1 and S2 are directly compared in terms of phase without making the signals pass the frequency multiplier 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluid measurement sensor that measures the movement of a fluid using ultrasonic waves. The present invention relates to a phase 1q adjustment type ultrasonic sensor suitable for use in a flowmeter.

``Prior art'' The conventional measurement method of an ultrasonic sensor for fluid measurement is to detect the movement of a fluid based on an oscillator signal and a received signal propagated within the fluid, as seen in Japanese Patent Publication No. 57-25141. There is a device that detects the phase change as a phase change of 1ffl.

FIG. 2 is a block diagram showing a conventional example of a Karman vortex flowmeter using an ultrasonic sensor. An ultrasonic sensor consisting of an ultrasonic transmitter 3 and an ultrasonic receiver 2 and 4 is arranged.

The ultrasonic transmitter 3 is driven by a drive circuit 5 to emit ultrasonic waves into the pipe l, and the emitted ultrasonic waves are caused by the movement of the fluid in the pipe l (in this example, after the vortex generator 2). The ultrasonic wave is received by the ultrasonic receiver 4 after being phase modulated by the Karman vortex (flow generated in the flow), and is input to the phase comparator 6. This phase comparator 6 uses the received signal S2 and the signal S from the oscillator.
1, and the modulation signal S3 caused by the vortex is
Take out.

The propagation characteristics of the ultrasonic waves used in the above-mentioned sensors differ depending on whether the medium is liquid or gas. For example, in a sensor that measures the flow rate of gas, the attenuation m of ultrasonic waves is large, so the reliability of transmission and reception must be considered. In a sensor that measures a liquid flow m, a relatively low frequency is selected, and in order to generate a sufficiently large phase modulation according to the flow velocity (flow m), λ, It is common to choose a high frequency.

That is, the phase change due to the vortex, lff1φ, is −Vφ−2π” c(c−v)′ “””■However,
r: Ultrasonic frequency, D: Pipe inner diameter C: Fluid sound velocity, ■
: Expressed by the equation vortex velocity, and from this 0 equation, when the fluid sound velocity is large and the vortex velocity is small (in liquid, for example underwater, C = 1
Measurement at 500 m/s, V-0, 1 m/s is required. ) The phase modulation mφ caused by the vortex is very small (and in order to reliably detect this, the ultrasonic frequency f must be increased.On the other hand, if the frequency f is high, the ultrasonic wave of the gas etc. When applied to a fluid that is difficult to penetrate and propagate, the attenuation m in the fluid increases, and the level of the ultrasonic signal received by the receiver decreases, making it impossible to detect vortices. However, increasing the drive voltage in order to obtain a sufficient reception level at low frequencies is undesirable in terms of explosion protection as it may cause sparks, etc. ``Problems to be Solved by the Invention'' However, If different frequencies are used for liquids, if a sensor for liquids with a high frequency is used for gases, the attenuation will be large and the reception level will be low; on the other hand, if a sensor for gases with a low frequency is used for liquids. In this case, there is a problem in that it is not possible to generate a sufficiently large phase modulation.

Therefore, it is necessary to apply different specifications to conventional ultrasonic sensors depending on the application, such as gas or liquid phase.
The problem was that it lacked versatility.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a reference skin sensor that can accurately measure fluids regardless of their physical properties.

"Means for Solving the Problems" In order to achieve the above object, the present invention provides a frequency doubling circuit in the path of a signal manually input to a phase comparator provided in an ultrasonic sensor.

"Operation" With the above configuration, while using stable low-frequency ultrasonic waves for transmission and reception, it is possible to increase the frequency by frequency doubling and obtain a large phase modulation signal to extract fluid movement (flow) signals. .

"Example" An embodiment of the present invention will be described below with reference to FIG.

Note that parts having the same functions as those in FIG. 2 are given the same reference numerals to simplify the explanation.

In the ultrasonic sensor of this embodiment, a frequency doubler 10 is provided in each path for supplying the transmitted signal S1 and the received signal S2 to the phase comparator 6, and a changeover switch 11 is used to control the original signals 5l-s2. Alternatively, the phase comparator 6 is supplied with a frequency-multiplied signal Sl'.82' obtained by doubling the frequency of the original signal 5l-s2.

By using the frequency doubler 10, it is possible to calculate the phase modulation mφ by supplying a signal with a higher frequency than the frequency radiated from the transmitter 3 or received by the receiver 4 to the phase comparator 6. Therefore, even if the frequency of the drive signal ultrasonic wave is set relatively low, a signal indicating the flow state with a sufficient S/N ratio can be obtained. Even in this case, there is no need to drive at a high voltage that would pose an explosion-proof problem.

Then, by switching the changeover switch 11 according to the physical properties of the fluid and measurement conditions, a route is selected that passes through the frequency multiplier 10, converts it into frequency-multiplied signals S1° and S2°, and supplies the signal to the phase comparator 6; By selecting a route in which the original signals S1 and S2 are directly supplied to the +11 comparator 6 without passing through the frequency doubler 10, it is possible to output a signal S3 indicating the flow state.

Therefore, it can be safely used with a wide range of fluids.
It is possible to stably transmit and propagate ultrasonic waves without requiring special circuits, and at the same time, it can be used under fluid conditions and measurement conditions where phase modulation caused by vortices (fluid movement) is reduced. , it is possible to obtain a phase modulation amount that can be detected reliably.

The above example describes the case where it is applied to a vortex flowmeter to detect Karman vortices, but the same applies to all sensors that detect the movement (flow) of the fluid to be measured by phase modulation of ultrasonic waves. produces the effect of Furthermore, although this embodiment has been described as a method of comparing the phases of the signal from the receiver and the signal from the oscillator in the phase comparator, by performing the phase comparison, the movement (flow) of the target fluid can be detected. If possible, phase comparison of any signal may be performed.

For example, the phases of two received ultrasonic signals propagating in opposite directions to the flow to be detected may be compared.

In addition, in this embodiment, the route that passes through the frequency doubling circuit and the route that does not go through it are switched and used, but depending on the applied fluid or measurement conditions, the changeover switch may be omitted and the frequency doubling process may be performed at all times. It's okay.

"Effects of the Invention" According to the present invention, low-frequency ultrasonic waves that can stably transmit and propagate through a wide range of fluids are used, and this signal is frequency-multiplied and then phase-compared. "flow"
Flow can be reliably detected even under fluid and measurement conditions where the phase modulation caused by the sensor becomes extremely small. Therefore, (1) A single sensor can be used for many fluids and measurement methods.

(2) Since it is not necessary to use high-frequency ultrasonic waves to increase the sensitivity of the sensor, there is no need to use high voltage to drive the sensor, which is advantageous in terms of explosion-proofing and other measures.

■ Low-frequency ultrasonic waves provide a received signal with a sufficient S/N ratio, so the S/N ratio required for high frequencies is reduced.
A special circuit for extracting and amplifying only the signal component from a signal with a poor N ratio becomes unnecessary.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a vortex flowmeter using an ultrasonic sensor of the present invention, and FIG. 2 is a block diagram of a vortex flowmeter using a conventional ultrasonic sensor. 1... Pipeline, 2... Vortex generator, 3...
...Zhao? °′Chang 1 oscillator, 4... Ultrasonic reception 2: (, 5... Drive circuit, (S......
Phase comparator, Sl...Outgoing signal, S2...
...Received signal, SF...Double frequency transmission signal, S2'
...... Double frequency reception signal, 10... Frequency doubler, 11...... Selector switch. Figure 1 Figure 2

Claims (1)

[Claims] an ultrasonic transmitter that is driven by a drive circuit to emit ultrasonic waves into a fluid to be measured; an ultrasonic receiver that receives the ultrasonic waves that have been phase-modulated by the movement of the fluid and converts them into electrical signals; An ultrasonic sensor comprising a phase demodulator for phase demodulating a signal received by the receiver, characterized in that a frequency doubling circuit is provided in a path for supplying signals to the phase demodulator.