JPH02206722A - Coriolis mass flowmeter - Google Patents

Abstract

PURPOSE:To reduce the influence of a noise caused by vibration of a piping by providing a pickup whose one end is connected to a first and a second straight pipe parts between a fixed frame and a coupling part, and which measures a displacement caused by Coriolis force between both the straight pipe parts. CONSTITUTION:An output of a pickup 17 passes through a first filter 19 and amplified by an amplifying circuit 21, and thereafter, inputted to a first sample- hold circuit 22. An output of a control pickup 18 passes through a second filter circuit 23, converts amplitude into a voltage by an amplitude detecting circuit 24, and thereafter, inputted to a driving circuit 25. An output of a temperature sensor 26 provided in the vicinity of an exciter 16 is inputted to a temperature detecting circuit 27, and inputted to a second sample-hold circuit 28. The driving circuit 25 supplies electric power of the exciter 16, and by the control pickup 18 and an output signal of the circuit 27, amplitude of the exciter 16 is adjusted. Outputs of a first and a second holding circuits 22, 28 are inputted to an A/D converter 29, and thereafter, digitized and inputted to a CPU 31, in which a temperature correction, a linearity correction and scaling are executed, and thereafter, a signal being proportional to a mass flow rate is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a Coriolis mass flowmeter with improved seismic resistance and a structure that is less susceptible to vibrations in main piping.

<Prior Art> FIG. 6 is a diagram illustrating the configuration of a conventional example that has been commonly used.

In the figure, reference numeral 1 is a U-shaped measurement tube whose both ends are attached to piping A.

2 is a flange for attaching the measuring tube 1 to the conduit A.

Reference numeral 3 denotes a vibrator provided at the tip of the U-shaped measuring tube 1.

4.5 are displacement detection sensors provided on both sides of the measuring tube 1, respectively.

In the above configuration, the measurement fluid is flowed through the measurement tube 1, and the vibrator 3 is driven. Angular velocity rω of the vibrator 3 in the vibration direction
J, the flow rate of the measured fluid rV, + (hereinafter the symbol enclosed in r'' represents a vector quantity), then Fc = -2m rω'' If you measure
Mass flow rate can be measured.

However, in general, the amplitude of vibrations proportional to Coriolis is extremely smaller than the amplitude of vibrations caused by excitation, and it is not possible to directly detect the amplitude of vibrations proportional to Coriolis.

Now, when viewed from the Z direction in Fig. 6, the vibration direction is divided into α and β due to the vibration of the vibrator 3, and the flow velocity is “v”.
As shown in FIGS. 7(A) and 7(B), the direction of Coriolis differs depending on the direction of , so that the phase is reversed and the measuring tube 1 vibrates while being twisted.

The displacement is detected by the displacement detection sensors 4 and 5, for example, a magnetic sensor, and the phase difference between the displacements of the displacement detection sensors 4 and 5 is (
The mass flow rate can be determined because it is proportional to (amplitude of vibration proportional to Coriolis)/(amplitude of vibration due to excitation).

Since the phase difference can be measured as the difference Δt in time at which the waveform crosses zero, Coriolis can be measured as a result.

FIG. 8 is a diagram illustrating the configuration of another conventional example that has been commonly used.

In this conventional example, the measuring tube 1 is of a two-tube type in order to reduce noise and obtain a large signal.

<Problems to be Solved by the Invention> However, in such a device, (1) the time difference is minute, and in order to detect it, circuits such as an amplifier circuit are complicated.

(2) In order to stably measure the phase difference, it is necessary to use a two-tube system as shown in Figure 8. (3) The measurement tube 1 is U-shaped, and the main axes A1 and A2 of the upstream and downstream piping are Since it protrudes only on one side, the U-shaped measuring tube easily vibrates when there is pipe vibration. That is, it has the disadvantage of weak earthquake resistance.

(4) As shown in FIG. 8, even if the measuring tube 1 has a structure of two overlapping pipes, it is difficult to improve earthquake resistance.

In order to improve earthquake resistance, the vibration fulcrum part 6.
A large-scale rigid structure is required to fix the 7.

The present invention solves this problem.

An object of the present invention is to provide a Coriolis mass flowmeter with improved earthquake resistance and a structure that is less susceptible to vibrations in the main piping.

Means for Solving the Problems> In order to achieve this object, the present invention provides a Coriolis mass flowmeter having a measuring pipe having a loop extending outward from a piping axis. a U-shaped measuring tube having a second straight pipe portion and having both ends fixed to the piping; Second
a fixing frame for fixing near both ends of each of the straight pipe sections; a connecting portion that connects the central portions of the second straight pipe portions to each other; a vibrator provided between the connecting portion and the fixed frame; and a vibration exciter provided between the fixed frame and the first connecting portion. ．． One end of each is connected to the second straight pipe section, and the first end is connected to the second straight pipe section. The present invention constitutes a Coriolis mass flowmeter characterized by comprising a pickup for measuring displacement due to Coriolis force between the second straight pipe sections.

Function> In the above configuration, the measurement fluid is flowed into the measurement tube, and the vibrator is driven. The first vibration is caused by the vibration exciter. The second straight pipe section vibrates in the same direction.

angular velocity rω in the vibration direction”, 1st. Assuming that the flow velocity of the measurement fluid flowing inside the second straight pipe section is "■", Fc = -2m r
Since the direction of Coriolika of ωJX rVj differs depending on the direction of the flow velocity rVj, the first. The second straight pipe section is deformed by the Coriolis force, and the first straight pipe section is deformed by the Coriolis force. The second straight pipe section is deformed. The measurement value with the pickup measures only the displacement due to the Coriolis force.

On the other hand, 1. Since the second straight pipe section is fixed near both ends with a fixed frame, it is difficult to receive external vibrations.Also, since there is a joint with a large mass in the center, external vibrations are absorbed by the two parallel pipes. There is a certain first. Since it acts in the same phase on the second straight pipe section, almost no external vibration is applied to the pickup.

Hereinafter, a detailed explanation will be given based on examples.

<Example> FIG. 1 is an explanatory diagram of the main part of an embodiment of the present invention.

In the figure, configurations with the same symbols as in FIG. 6 represent the same functions.

Hereinafter, only the differences from FIG. 6 will be explained.

11 are first parallel to each other. This is a U-shaped measuring tube having a second straight pipe portion 12°13 and fixed to piping A at both ends.

14 is the first. This is a fixing frame that fixes near both ends of each of the second straight pipe sections 12.13.

15 is the first. This is a connecting portion that connects the central portions of the second straight pipe portions 12.13 to each other.

Reference numeral 16 denotes a vibrator provided between the coupling portion 15 and the fixed frame 14.

17 has one end connected to the first and second straight pipe parts 12 and 13 between the fixed frame 14 and the coupling part 15, respectively. This is a pickup that measures the displacement due to the Coriolis force between the second straight pipe portions 12 and 13.

18 is an adjustment pickup for adjusting the amplitude of the vibrator 16 to a constant value.

FIG. 2 shows one embodiment of the converter.

The output of the pickup 17 passes through the first filter 19,
After being amplified by the amplifier circuit 21, it enters the first sample and hold circuit 22.

The output of the adjustment pickup 18 is sent to the second filter circuit 2.
3, and after converting the amplitude into voltage in the amplitude detection circuit 24,
It is input to the drive circuit 25.

The output of a temperature sensor 26 provided near the vibrator 16 is input to a temperature detection circuit 27, and the output thereof is input to a second sample hold circuit 28.

The drive circuit F625 supplies power to the vibrator 16. Further, the amplitude of the vibrator 16 is adjusted by the output signals of the adjustment pickup 18 and the temperature detection circuit 27.

The outputs of the first and second sample and hold circuits 22 and 28 are:
After being input to the A/D converter 29, the digitized signal is input to the CPU 31.

After performing temperature correction, linearity correction, and scaling, the CPU 31 outputs a signal proportional to the mass flow rate.

In the above configuration, the measurement fluid is flowed into the measurement tube 11,
The vibrator 16 is driven. The first . Second
The straight pipe sections 12,13 vibrate in the same direction.

Angular velocity in the vibration direction “ω1, 1st and 2nd straight pipe portions 12°13
Assuming the flow velocity ryJ of the fluid to be measured flowing through the inside of the
The direction of Coriolis varies depending on the direction of the flow velocity r V J. The second straight pipe section 12.13 is deformed by the Coriolis force, and the first straight pipe section 12.13 is deformed by the Coriolis force. The second straight pipe section 12.13 is
It is deformed as shown in FIG. The measurement value by the pickup 17 measures the change in length Δ1(t) between a and a, and the adjustment pickup 18 measures the change in length ΔL(t) between b and b.

here, Δl (t) = l (t)-1.

ΔL (t) = L (t) - LO l(1): Length at 1 hour L (t): Length at time Io: Length before excitation Lo: Length before excitation Pick up The change in measured value Δ1(1) at 17 measures only the displacement due to the Coriolis force. It is shown in solid line in FIG.

The output of the pickup 17 input to the converter is subjected to noise removal in the first filter circuit 19, and then amplified in the first amplifier circuit 21, and the peak value is sampled by the first sample and hold circuit. As can be seen from FIG. 5, the peak value is proportional to the Coriot force, so a voltage proportional to the mass flow rate can be sampled.

On the other hand, 1. The second straight pipe section 12.13 has a fixed frame 1 near both ends.
4, which is fixed at the first and second tubes, so that external vibrations are easily absorbed.Also, since there is a coupling part 15 with a large mass in the center, external vibrations are absorbed by the two parallel tubes, the first and second tubes. Second straight pipe section 12.13
Since the pickup 17 operates in the same phase as the pickup 17, almost no external vibration is applied to the pickup 17.

As a result, a Coriolis mass flowmeter with improved seismic resistance is obtained, with less influence of noise due to vibrations of complex piping.

<Effects of the Invention> As explained above, the present invention provides a Coriolis mass flowmeter including a measurement pipe having a loop projecting outward from a piping axis. a U-shaped measuring tube having a second straight pipe portion and having both ends fixed to the piping; Second
a fixing frame for fixing near both ends of each of the straight pipe sections; a connecting portion that connects the central portions of the second straight pipe portions to each other; a vibrator provided between the connecting portion and the fixed frame; and the first connecting portion between the fixed frame and the connecting portion. ．． One end of each is connected to the second straight pipe section, and the first end is connected to the second straight pipe section. A Coriolis mass flowmeter is provided, comprising a pickup for measuring displacement due to Coriolis force between the second straight pipe sections.

As a result, a Coriolis mass flowmeter with improved seismic resistance is obtained, with less influence of noise due to vibrations of complex piping.

Therefore, according to the present invention, it is possible to realize a Coriolis mass flowmeter with improved earthquake resistance and a structure that is less susceptible to vibrations of the main pipe.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the main part of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the main part of an embodiment of the converter shown in FIG. 1, and FIG.
4 and 5 are diagrams explaining the operation of Figure 1, Figure 6 is a diagram explaining the configuration of a conventional example commonly used, Figure 7 is a diagram explaining the operation of Figure 6, and Figure 8 is a diagram explaining the operation of Figure 6. FIG. 2 is a diagram illustrating the configuration of another conventional example that has been commonly used. 2...Flange mounting, 11...Measuring tube, 12...
・First straight pipe part, 13... Second straight pipe part, 14... Fixed frame, 15... Coupling part, 16... Exciter, 17...
Pickup, 18...adjustment/pickup, 19.
...First filter circuit, 21...Amplification circuit, 22.
...First sample hold circuit, 23...Second filter circuit, 24...Amplitude detection circuit, 25...Drive circuit, 26...Temperature sensor, 27...Temperature detection circuit, 28...・Second sample hold circuit, 29...A
/D converter, 31...CPU, A...Piping. Figure 4 Figure 3 Figure 5 Figure 7 (A) (B) Figure 8

Claims (1)

[Scope of Claims] A Coriolis mass flowmeter equipped with a measurement tube having a loop extending outward from a piping axis, which has first and second straight pipe portions parallel to each other, has a U-shape, and has both ends connected to the piping. a measuring tube fixed to the
a fixing frame that fixes near both ends of each of the straight pipe parts; a coupling part that couples the first and second straight pipe parts near the center to each other; and a fixing frame provided between the coupling part and the fixing frame. an exciter; and a pickup, one end of which is connected to each of the first and second straight pipe sections between the fixed frame and the coupling section, and which measures displacement due to the Coriolis force between the first and second straight pipe sections. A Coriolis mass flowmeter characterized by comprising: