JP3259201B2 - Flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter using ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, as an example of a flow meter using ultrasonic waves, there is an ultrasonic vortex flow meter for gas using gas as a fluid to be measured. This gas ultrasonic vortex flowmeter radiates ultrasonic waves into the gas, and a vortex generator that is provided in the pipe and generates a Karman vortex on the downstream side. An ultrasonic transmitter, an ultrasonic receiver that receives ultrasonic waves from the ultrasonic transmitter through Karman vortices in gas, and outputs a flow signal proportional to a flow rate based on a signal from the ultrasonic receiver. It is generally composed of an arithmetic circuit and utilizes the fact that the degree of frequency modulation of ultrasonic waves by Karman vortices is proportional to the flow rate. The ultrasonic vortex flowmeter for gas emits ultrasonic waves into the gas, demodulates the frequency modulation received from the Karman vortex with an arithmetic circuit, detects the number of generated Karman vortices, and calculates the number of generated Karman vortices. The flow velocity of the gas, and hence the flow rate, is measured based on the measured flow velocity.

[0003]

By the way, since ultrasonic waves are relatively hard to propagate in gas, the receiving voltage is low and the receivable frequency band is narrow. Since the degree of frequency modulation increases as the flow rate increases, the transmitted ultrasonic frequency at the time of the high flow rate exceeds the receivable frequency band, and there is a possibility that reception becomes impossible. In addition, since the receivable frequency band is narrow, the resonance frequencies of the ultrasonic transmitter and the ultrasonic receiver must be matched with high accuracy, and the characteristic management is not easy. It is conceivable to use an ultrasonic receiver with a wide receivable frequency band in order to improve the above-mentioned problems. However, in reality, it cannot be applied as it is due to restrictions on the characteristics and structure of elements. Met.

[0004] The present invention has been made in view of the above circumstances, and has as its object to provide a flowmeter capable of receiving ultrasonic waves stably in a wide frequency range.

[0005]

In order to achieve the above object, the present invention provides a pipe through which a fluid flows, and a pipe provided in the pipe.
A vortex generator for generating Karman vortices downstream Te, an ultrasonic transmitter that radiates ultrasonic waves to the fluid in the conduit, receives the ultrasonic wave from the ultrasonic transmitter through the Karman vortex A plurality of ultrasonic receivers, and an arithmetic circuit that outputs a flow signal proportional to the flow rate based on signals from the plurality of ultrasonic receivers, wherein the plurality of ultrasonic receivers The present invention is characterized in that receivable frequency bands are set to be shifted from each other and partially overlapped.

[0006]

With this configuration, the entire receivable frequency band can be set to a range wider than the transmittable frequency band of the ultrasonic transmitter, and the ultrasonic transmitter emits ultrasonic waves by setting in this manner. Even if it is modulated by the Karman vortex, the modulated ultrasonic waves will be received over a wide range of frequencies. By setting the receivable frequency bands of a plurality of ultrasonic receivers to be slightly shifted, ultrasonic waves can be received over a wide range, so that the ultrasonic transmitters and the plurality of ultrasonic receivers are accurately matched in resonance frequency. You don't have to. For this reason, the characteristic management can be eased by omitting the high-precision matching of the resonance frequency, and the production can be simplified.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flow meter according to an embodiment of the present invention will be described below with reference to FIGS. In the drawing, a vortex generator 2 for generating Karman vortices is provided on a downstream side of a pipe 1 through which a fluid such as gas flows. In the Karman vortex generation region of the pipe 1, an ultrasonic transmitter 3 for obtaining information on the flow of the fluid,
First and second ultrasonic receivers 4 and 5 are provided side by side on the same circumference. When the ultrasonic transmitter 3 radiates the ultrasonic signal J generated by the oscillator 6 connected to the ultrasonic transmitter 3 into the fluid, the ultrasonic waves propagating in the fluid are modulated by the Karman vortex according to the flow rate. The first and second ultrasonic receivers 4 and 5 receive the signals.

As shown in FIG. 2A, the ultrasonic transmitter 3 sets a transmittable frequency band A centered on a frequency f ₀ . As shown in FIG. 2B, a receivable frequency band B that minimizes the frequency f ₀ is set for the first ultrasonic receiver 4, and the second ultrasonic receiver 5 is set for the second ultrasonic receiver 5.
As shown in FIG. 2B, a receivable frequency band C having a maximum value of the frequency f ₁ (f ₀ <f ₁ ) is set, and the first and second ultrasonic receivers 4, 5 , The respective receivable frequency bands B and C are shifted, and the frequencies f ₀ to f ₁
Are superimposed at the portion, and the entire receivable frequency band D is continuous.

An arithmetic circuit 7 is connected to the first and second ultrasonic receivers 4 and 5 and the oscillator 6. The arithmetic circuit 7 includes first and second amplifiers 8 and 9 connected to the first and second ultrasonic receivers 4 and 5, and first and second amplifiers 8 and 9,
And a demodulator 10 for inputting a signal from the demodulator and demodulating the signal, and a flow signal K proportional to the flow rate based on the signal from the demodulator 10.
And an output circuit 11 for outputting the same.

In the flowmeter configured as described above, the entire receivable frequency band D is set to a range wider than the receivable frequency band A of the ultrasonic transmitter 3, and the ultrasonic transmitter 3 Even if a sound wave is emitted and is modulated by the Karman vortex, the modulated ultrasonic wave can be reliably received and the flow rate can be measured with high accuracy. Further, even if the flow of the fluid becomes a high flow rate and the degree of frequency modulation becomes large, it can be received and the flow rate can be properly measured.

As described above, by setting the receivable frequency bands B and C of the first and second ultrasonic receivers 4 and 5 to be slightly shifted, ultrasonic waves can be received over a wide range. It is not necessary to match the resonance frequencies of the receiver 3, the first and second ultrasonic receivers 4, 5 with high accuracy.
For this reason, the characteristic management can be eased by omitting the high-precision matching of the resonance frequency, and the production can be simplified.

In this embodiment, the ultrasonic receivers are first and second ultrasonic receivers.
As an example, two ultrasonic receivers 4 and 5 were used.
Three or more ultrasonic receivers may be used. Further, in the present embodiment, the case where the ultrasonic transmitter 3, the first and second ultrasonic receivers 4, 5 are provided side by side on the same circumference is taken as an example, but the present invention is not limited to this. Instead, it may be provided at any position as long as it can transmit and receive.

[0013]

Since the present invention is a flow meter constructed as described above, the whole receivable frequency band is set to a range wider than the transmittable frequency band of the ultrasonic transmitter and modulated by Karman vortex. Since the transmitted ultrasonic waves are received over a wide range of frequencies, the flow rate can be measured accurately and stably. By setting the receivable frequency bands of a plurality of ultrasonic receivers to be slightly shifted, ultrasonic waves are received over a wide range and the ultrasonic transmitter does not perform high-precision matching of the resonance frequencies of the plural ultrasonic receivers. Since the matching of the resonance frequency with high accuracy is omitted, the characteristic management can be eased, and the production can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a flow meter according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing frequency bands of an ultrasonic transmitter and first and second ultrasonic receivers of the flow meter.

[Explanation of symbols]

 Reference Signs List 1 conduit 3 ultrasonic transmitter 4 first ultrasonic receiver 5 second ultrasonic receiver 7 arithmetic circuit B receivable frequency band of first ultrasonic receiver C reception of second ultrasonic receiver Possible frequency band D Overall receivable frequency band

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-288800 (JP, A) JP-A-64-78114 (JP, A) JP-A-3-274418 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G01F 1/32

Claims (1)

(57) [Claims] 1. A pipe through which a fluid flows, and a pipe provided in the pipe.
A vortex generator for generating Karman vortices downstream Te, an ultrasonic transmitter that radiates ultrasonic waves to the fluid in the conduit, receives the ultrasonic wave from the ultrasonic transmitter through the Karman vortex A plurality of ultrasonic receivers, and an arithmetic circuit that outputs a flow signal proportional to the flow rate based on signals from the plurality of ultrasonic receivers, wherein the plurality of ultrasonic receivers A flowmeter wherein receivable frequency bands are set to be shifted from each other and partially overlapped.