JP2012026776A - Coriolis-type mass flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a coriolis-type mass flowmeter for making it difficult to receive the influence of disturbance oscillation or a signal noise or the like, and for reducing a circuit scale at low costs.SOLUTION: This coriolis-type mass flowmeter is configured such that measurement object fluid is made to flow in an oscillating oscillation tube, and that the oscillation tube is made to deform and oscillate with a coriolis force generated by the flow and the angular oscillation of the oscillation tube, and that the oscillation of the oscillation tube is detected by an oscillation detection sensor, and that the mass flow rate of the measurement object fluid flowing in the oscillation tube is measured, and provided with: an oscillation means for making the oscillation tube perform resonant oscillation in a secondary mode; a first oscillation detection sensor for detecting the amplitude of the oscillation tube which performs resonant oscillation in the secondary mode; a second oscillation detection sensor for detecting the amplitude of the vertical oscillation of the oscillation tube with the coriolis force; and an arithmetic control means for calculating the mass flow rate of the measurement object fluid based on the detection signal of the first oscillation detection sensor, and the oscillation means is characterized to adjust the amplitude of the oscillation based on the detection signal of the first oscillation detection sensor.

Description

  The present invention allows a fluid to be measured to flow in a vibration tube (sensor tube) that is vibrated by vibration means (excitation means) composed of a coil and a magnet, and deforms the vibration tube by the Coriolis force generated by the flow and the angular vibration of the vibration tube. A Coriolis mass flowmeter that measures the mass flow rate of a fluid to be measured that flows through the vibration tube by detecting the displacement of the vibration tube with the first vibration detection sensor and the second vibration detection sensor, and is low-cost and circuit scale The present invention relates to a Coriolis mass flow meter having a small size, a low cost, small circuit scale, and being hardly affected by disturbance vibrations or signal noise.

4A and 4B are configuration explanatory views showing an example of a conventional Coriolis mass flow meter, where FIG. 4A is an overall configuration diagram, and FIGS. 4B and 4C are explanatory diagrams of vibrations of a vibration tube.
In FIG. 4, a conventional Coriolis type mass flow meter is configured to vibrate a vibrating tube (sensor tube) 1 through which a fluid to be measured flows by a vibrating means (exciting means) 2 and relative displacement of the vibrating tube 1 by Coriolis force proportional to the flow rate. Is detected by two vibration detection sensors 3 and 4 (electromagnetic pickup or the like).

  Further, the conventional Coriolis type mass flowmeter calculates the mass flow rate by calculating the amount corresponding to the torsion angle of the vibration tube caused by the Coriolis force based on the detection signals from the vibration detection sensors 3 and 4 by phase difference detection. Arithmetic control means (not shown) is also provided.

The vibration tube 1 is provided on a base 5 having an inlet at one end and an outlet (not shown) at the other end, and both ends are connected to the base 5 so as to communicate with these inlet and outlet. This is a U-shaped sensor tube.
The vibration means 2 and the vibration detection sensors 3 and 4 are both composed of a magnet such as a coil and a permanent magnet (voice coil type vibration mechanism and detection mechanism).

  In the vibration tube 1, the vibration detection sensor 3, the vibration means 2, and the vibration detection sensor 4 are installed in this order along the flow direction of the fluid to be measured. In particular, the vibration detection sensors 3 and 4 are U-shaped straight tube portions of the vibration tube 1 and are provided at positions facing each other.

The Coriolis mass flow meter 10 configured as described above mainly measures the mass flow rate of the fluid to be measured as follows.
(1) The fluid to be measured flows into the vibrating tube 1 through the inlet of the base 5.
(2) An (alternating) current is supplied to an excitation coil or the like (not shown) of the vibration means 2 and the vibrating tube 1 is vibrated by electromagnetic action with a magnet (not shown).
Specifically, as shown in FIG. 4B, the vibration means 2 vibrates the vibration tube 1 up and down like a cantilever beam around the fixed end at a resonance frequency.

(3) Coriolis force having a magnitude corresponding to the mass of the fluid to be measured is applied to the vibration tube 1 due to the vibration speed associated with the rising or lowering of the vibration tube 1.
Since this Coriolis force is directed in the opposite direction on the inflow side and the outflow side of the fluid to be measured, the twist occurs as shown in FIG. 4C, and the vibration tube 1 vibrates while being twisted. This twist angle is proportional to the mass flow rate of the fluid to be measured.

  Here, when the angular velocity “ω” in the vibration direction of the vibration means 2 and the flow velocity “V” of the measurement fluid (hereinafter, the symbol surrounded by “” represents a vector quantity), the amplitude of the vibration caused by the Coriolis force is Fc = −2 m “ω” × “V”. For this reason, if the amplitude of vibration proportional to the Coriolis force is measured by the vibration detection sensors 3 and 4, the mass flow rate can be measured.

However, in general, the amplitude of vibration proportional to the Coriolis force is extremely smaller than the amplitude of vibration caused by excitation, and the amplitude of vibration proportional to the Coriolis force cannot be directly detected.
Therefore, in the conventional Coriolis type mass flow meter, the displacement is detected by the vibration detection sensors 3 and 4 as in the following (4) and (5), and the phase difference of the displacement of the tube (the amplitude of vibration proportional to the Coriolis force). ) / (Coriolis force is measured using the fact that it is proportional to the amplitude of vibration due to vibration).

(4) The vibration detection sensors 3 and 4 detect the vibration of the vibration tube 1 and an operation control means (arithmetic circuit) in a control device (not shown) via a signal line (not shown) of the detection signal. To send.

(5) The calculation control means calculates the mass flow rate of the fluid under measurement from the phase difference (time difference) based on the detection signals from the vibration detection sensors 3 and 4 and displays the result on the display means (not shown). .
Since the phase difference can be measured as the time difference Δt when the waveform crosses zero, the Coriolis force can be measured as a result.

  As described above, the conventional Coriolis type mass flowmeter allows a fluid to be measured to flow in a vibration tube (sensor tube) that is vibrated by vibration means (excitation means) composed of a coil and a magnet, and the flow and angular vibration of the vibration tube. The vibration tube is deformed and vibrated by the Coriolis force generated by, and the mass flow rate of the fluid to be measured flowing through the vibration tube can be measured by detecting the displacement of the vibration tube by the first vibration detection sensor and the second vibration detection sensor.

  For example, there is Patent Document 1 below as a prior art document related to a conventional Coriolis mass flow meter.

JP-A-6-317444

  However, in the conventional Coriolis type mass flowmeter, the phase difference between the two vibration detection sensors is very small, about several urads to several mrad, and high-precision phase difference measurement is required, and the circuit scale of the phase difference calculation circuit is large. There was a problem that the burden of cost would also become large.

  In addition, in the conventional Coriolis type mass flow meter, the displacement due to the Coriolis force is as small as about 1/1000 compared to the displacement due to the drive, so when a disturbance vibration is applied and overlaps with the displacement due to the Coriolis force, the vibration detection sensor There was a problem that the output of was greatly disturbed. Therefore, there is a problem that the mass flow rate cannot be measured with high accuracy.

  For example, factors that disturb the output from the vibration detection sensor include signal noise due to electromagnetic fields mixed in the vibration detection sensor and signal noise of the signal processing circuit that amplifies the vibration detection sensor output in addition to disturbance vibration. Cause disturbance of the output.

  A filter circuit is generally used to separate a signal caused by such disturbance vibration or noise from a signal that is truly desired to be measured. However, this circuit has a large circuit scale and a high cost burden. There was a point.

  The present invention solves such problems, and its purpose is low-cost and small-scale Coriolis mass flowmeter, low-cost and small-scale circuit, affected by disturbance vibration and signal noise. It is to realize a difficult Coriolis mass flow meter.

In order to achieve the above object, the invention described in claim 1 of the present invention is:
A fluid to be measured is caused to flow through the vibrating tube, and the vibrating tube is deformed and vibrated by the flow and the Coriolis force generated by the angular vibration of the vibrating tube, and the vibration of the vibrating tube is detected by a vibration detection sensor. In a Coriolis mass flow meter for measuring a mass flow rate of a fluid to be measured flowing in a tube, a vibration means for resonantly vibrating the vibrating tube in a secondary mode and an amplitude of the vibrating tube for resonantly vibrating in the secondary mode are detected. The mass flow rate of the fluid to be measured is calculated based on the detection signal of the first vibration detection sensor, the second vibration detection sensor that detects the amplitude of the vertical vibration of the amplitude tube due to the Coriolis force, and the detection signal of the second vibration detection sensor. And a vibration control unit configured to control the amplitude of the vibration based on a detection signal from the second vibration detection sensor. Characterized by an integer.

The invention according to claim 2 is the Coriolis type mass flow meter according to claim 1,
The vibration tube is formed in a U shape, the vibration means is disposed in one U-shaped straight tube portion of the vibration tube, and the first vibration detection sensor is formed in a U shape of the vibration tube. It is arranged in the other straight pipe part, and the second vibration detection sensor is arranged in a U-shaped curved pipe part of the vibration tube.

The invention according to claim 3 is the Coriolis mass flowmeter according to claim 1 or 2,
The vibration means adjusts the amplitude of the resonance vibration of the secondary mode of the vibration tube to a predetermined amplitude based on a detection signal from the second vibration detection sensor.

  According to a fourth aspect of the present invention, in the Coriolis mass flowmeter according to any one of the first to third aspects, a drive signal applied to the coil of the vibration means or a detection signal from the second vibration detection sensor is provided. Signal processing means for synchronously detecting the detection signal of the first vibration detection sensor as a reference signal is provided.

  According to a fifth aspect of the present invention, in the Coriolis mass flow meter according to the fourth aspect, the reference signal is substantially equal to a frequency of vertical vibration in the vicinity of the second vibration detection sensor.

  According to the present invention, the vibration means for resonating vibration of the vibration tube in the secondary mode, the first vibration detection sensor for detecting the amplitude of the vibration tube resonating in the secondary mode, and the vertical vibration of the amplitude tube by Coriolis force. And a calculation control means for calculating a mass flow rate of the fluid to be measured based on a detection signal of the second vibration detection sensor. The vibration means is a first vibration detection sensor. The Coriolis force proportional to the mass flow rate can be measured by the vibration amplitude by adjusting the amplitude of the vibration based on the detection signal by the above, so that a Coriolis type mass flow meter with a small circuit scale can be realized at a low cost.

  According to the fourth and fifth aspects, the vibration means for resonantly vibrating the vibration tube in the secondary mode, the first vibration detection sensor for detecting the amplitude of the vibration tube that resonantly vibrates in the secondary mode, and the amplitude tube based on Coriolis force A second vibration detection sensor for detecting the amplitude of the vertical vibration of the fluid, and an arithmetic control means for calculating the mass flow rate of the fluid to be measured based on the detection signal of the second vibration detection sensor. The amplitude of the vibration is adjusted based on the detection signal from the detection sensor, and the detection signal of the first vibration detection sensor is synchronized with the drive signal applied to the coil of the vibration means or the detection signal from the second vibration detection sensor as a reference signal. By providing signal processing means for detection, Coriolis force proportional to mass flow rate can be detected by vibration amplitude, and vibration frequency by Coriolis force is vibration frequency by vibration means. Utilizing be equal can be realized, the circuit scale is small Coriolis mass flowmeter in affected hardly cost of such disturbance vibration and signal noise.

It is composition explanatory drawing which shows one Example of the Coriolis type | mold mass flowmeter of this invention. It is explanatory drawing of the vibration state of the vibration tube of the Coriolis type | mold mass flowmeter of FIG. It is composition explanatory drawing of the other Example of the Coriolis type | mold mass flowmeter which concerns on this invention. It is composition explanatory drawing which shows an example of the conventional Coriolis type | mold mass flowmeter.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a structural explanatory view showing an embodiment of the Coriolis mass flow meter of the present invention. The same parts as those in FIG.

  The difference between FIG. 1 and FIG. 4 is that the vibration means for resonating the vibration tube in the secondary mode, the first vibration detection sensor for detecting the amplitude of the vibration tube resonating in the secondary mode, and the Coriolis force are used. A second vibration detection sensor for detecting an amplitude of vertical vibration of the amplitude tube; and an arithmetic control means for calculating a mass flow rate of the fluid to be measured based on a detection signal of the second vibration detection sensor. The feature is that the amplitude of vibration is adjusted based on the detection signal from the first vibration detection sensor, the drive signal applied to the coil of the vibration means or the detection signal from the second vibration detection sensor as the first reference signal. It is a point provided with the signal processing means which carries out synchronous detection of the detection signal of this vibration detection sensor.

(Description of configuration)
In FIG. 1, a Coriolis mass flow meter 20 according to the present invention mainly includes a vibration tube 1 through which a fluid to be measured flows, a vibration means (excitation means) 6 that vibrates the vibration tube 1, and resonance vibration in a secondary mode. A first vibration detection sensor 7 such as a first pickup for detecting the amplitude of the vibrating tube 1 to be detected, and a second vibration detection sensor for detecting the amplitude (displacement) of the vertical vibration of the amplitude tube due to the Coriolis force proportional to the flow rate. 8, a base 5 such as a support tube through which a fluid having an inflow port at one end and an outflow port (not shown) at the other end, a drive signal applied to the coil of the vibration means 6, or a first vibration detection sensor 7 The signal processing means 9 for synchronously detecting the detection signal of the second vibration detection sensor 8 using the detection signal by the reference signal as the reference signal, and the mass flow rate of the fluid to be measured based on the detected detection signal of the second vibration detection sensor 8 Arithmetic control means for output (not shown), and a.

  The Coriolis mass flow meter 20 of the present invention does not include the signal processing means 9 as an essential component. For example, when the detection signal of the second vibration detection sensor 8 is hardly affected by disturbance vibration or signal noise, the signal processing means 9 may or may not be provided.

  The vibration tube 1 is provided on a base 5 having an inlet at one end and an outlet (not shown) at the other end, and both ends are connected to the base 5 so as to communicate with these inlet and outlet. It is the tube for the U-shaped sensor made.

  The vibration means 6, the first vibration detection sensor 7, and the second vibration detection sensor 8 are all composed of a magnet such as a coil and a permanent magnet (voice coil type vibration mechanism, detection mechanism).

An inflow side flow path extending from the inflow port and an outflow side flow channel (not shown) connected to the outflow port are formed inside the base 5, and both ends of the vibration tube 1 are connected to the inflow side flow. The base 5 is connected so as to communicate with the channel and the outflow side flow path.
Therefore, the fluid to be measured supplied into the base 5 from the inflow port flows into the vibration tube 1 through the inflow side flow channel, and further flows out to the outside through the outflow side flow channel at the outflow port.

  The vibration means 6 causes the vibration tube 1 to resonate in a secondary mode. For example, as shown in FIG. 1, the vibration means 6 is installed in a U-shaped straight pipe portion on the fluid inflow side of the vibration tube 1. The magnet of the vibration means 6 is arranged so that the same magnetic pole is inserted into the excitation coil, for example, similarly to the vibration detection sensor 1.

  The (excitation) coil of the vibration means 6 is supplied with an (alternating) current having a frequency substantially equal to the natural frequency of the vibration tube 1, and by this current supply, an attractive force and a repulsive force act on the magnet. The vibration tube 1 vibrates due to the electromagnetic interaction.

Further, the vibration means 6 adjusts the amplitude of the vibration based on the detection signal from the first vibration detection sensor 7 so as to keep the amplitude of the secondary mode resonance vibration of the vibration tube 1 at a predetermined amplitude.
That is, in the Coriolis mass flow meter 20, the first vibration detection sensor 7 detects the vibration caused by the vibration means 6, and outputs this detection signal to the vibration means 6, and the vibration means 6 applies feedback based on the detection signal. The vibration amplitude of the vibration tube 1 is kept constant.

  The first vibration detection sensor 7 detects the amplitude (displacement) of the vibration tube 1. For example, as shown in FIG. 1, the first vibration detection sensor 7 is installed in a straight tube portion on the outflow side of the U-shaped fluid of the vibration tube 1.

  The second vibration detection sensor 8 detects the amplitude (displacement) of the vertical vibration generated by the Coriolis force of the vibration tube 1. For example, as shown in FIG. 1, the second vibration detection sensor 8 is installed in the vicinity of a U-shaped curved tube portion of the vibration tube 1.

  The first vibration detection sensor 7 and the second vibration detection sensor 8 include a detection coil and a magnet attached to the vibration tube 1. Each magnet is arranged such that, for example, the same magnetic pole is inserted into the detection coil. In the first vibration detection sensor 7 and the second vibration detection sensor 8, when a relative displacement is generated between the detection coil and the magnet, an electromagnetic induction current flows through the detection coil, and the first vibration detection sensor 7 and the second vibration detection sensor 8 correspond to the vibration (speed) of the vibration tube 1. The detection signal of the specified size is output.

The signal processing means 9 synchronously detects the detection signal of the second vibration detection sensor 8 using the drive signal applied to the coil of the vibration means 6 or the detection signal from the first vibration detection sensor 7 as a reference signal. For this reason, vibration frequency components other than the vertical vibration frequency in the vicinity of the second vibration detection sensor 8 can be removed by signal processing with respect to the influence of disturbance vibration and signal noise.
Here, since the vibration means 6 causes the vibration tube 1 to resonate and vibrate in the secondary mode to vertically vibrate the straight tube portion of the tube, the vibration frequency due to the Coriolis force generated when the fluid flows in is the vibration frequency by the vibration means. Is equal to
That is, it can be said that the vibration frequency of the above-described reference signal (drive signal or the like) is substantially equal to the vertical vibration frequency in the vicinity of the second vibration detection sensor 8.

  An arithmetic control unit (not shown) measures the Coriolis force based on the detected detection signal of the second vibration detection sensor 8 and calculates the mass flow rate of the fluid to be measured.

FIG. 2 is an explanatory diagram of the vibration state of the vibration tube of the Coriolis mass flow meter of FIG.
In FIG. 2, the vibration tube 1 vibrates as described below.
When the flow rate of the fluid flowing through the vibration tube 1 excited in the secondary mode by the vibration means 6 is 0 (zero), the two U-shaped straight pipe portions vibrate up and down alternately (up or down). And vibrate). The two U-shaped straight tube portions of the vibration tube 1 vibrate up and down symmetrically with respect to, for example, the vicinity of the central portion of the U-shaped bent tube portion.

  When a fluid flows into the vibration tube 1 excited in the secondary mode by the vibration means 6, a Coriolis force is generated by the vibration described above, and a U-shaped curved tube portion (second vibration detection) of the vibration tube 1 is generated. The vicinity of the position of the sensor 8) starts vertical vibration at the same frequency as the frequency of vibration by the vibration means 6. The amplitude of this vertical vibration is proportional to the Coriolis force proportional to the mass flow rate of the fluid.

  Specifically, when a fluid flows, the vibration tube 1 vibrates while being twisted by applying Coriolis force to the vertical vibration of each U-shaped straight tube portion, and the U-shaped curved tube portion (second vibration detection) The vicinity of the position of the sensor 8 vibrates up and down at the same frequency as the vibration frequency of the vibration means 6.

In the Coriolis type mass flow meter 20 of the present invention, the calculation control means determines the mass flow rate of the fluid to be measured based on the vertical vibration amplitude proportional to the Coriolis force of the vibration tube 1 detected by the second vibration detection tube 8. taking measurement.
In other words, the Coriolis type mass flow meter 20 can detect the Coriolis force proportional to the mass flow rate by the vibration amplitude by adopting the above-described configuration. Therefore, the circuit configuration of the calculation control means is a phase difference calculation circuit with a large circuit scale and cost burden for measuring “a very small phase difference of about several urads to several mrad” like a conventional Coriolis mass flowmeter. This is not necessary and is mainly composed of a multiplier, which is effective in reducing the circuit scale.

  Note that the first vibration detection sensor 7 and the vibration means 6 are electrically connected via a connection line. The arithmetic control means is electrically connected to the signal processing means 9 via a connection line. Further, the signal processing means 9 is electrically connected to the first vibration detection sensor 7 and the second vibration detection sensor 8 via connection lines, respectively. The arithmetic control means may be electrically connected to the first vibration detection sensor 7 and the second vibration detection sensor 8 via connection lines, respectively.

(Description of operation)
The Coriolis mass flowmeter 20 of the present invention has the configuration as described above, and mainly measures the mass flow rate of the fluid to be measured as follows.
(1) A current is supplied to an excitation coil or the like (not shown) of the vibration means 6 to resonate and vibrate the vibration tube 1 in the secondary mode by electromagnetic action with a magnet (not shown).
(2) The first vibration detection sensor 7 detects the amplitude (displacement) of the vibration tube 1 and outputs this detection signal to the vibration means 6.

(3) The vibration means 6 keeps the vibration amplitude of the vibration tube 1 constant by applying feedback based on the detection signal from the first vibration detection sensor 7.
At this time (when the flow rate is 0), the two U-shaped straight pipe portions vibrate up and down alternately. For example, the two U-shaped straight pipe portions are at the center of the U-shaped curved pipe portion. Vibrates up and down symmetrically around the vicinity.

(4) The fluid to be measured flows into the vibrating tube 1 through the inlet of the base 5. At this time (when the fluid flows in), the vibrating tube 1 vibrates while twisting by applying Coriolis force to the vertical vibration of the two U-shaped straight tube portions, and the U-shaped bent tube portion (second The vicinity of the position of the vibration detection sensor 8 vibrates up and down at the same frequency as the vibration frequency of the vibration means 6.
(5) The second vibration detection sensor 8 detects the amplitude (displacement) of the vertical vibration generated by the Coriolis force of the vibration tube 1.

(6) The signal processing means 9 synchronously detects the detection signal of the second vibration detection sensor 8 using the drive signal applied to the coil of the vibration means 6 or the detection signal from the first vibration detection sensor 7 as a reference signal.
For this reason, vibration frequency components other than the vertical vibration frequency in the vicinity of the second vibration detection sensor 8 can be removed by signal processing with respect to the influence of disturbance vibration and signal noise.
(7) The calculation control means calculates the mass flow rate of the fluid to be measured based on the detected detection signal of the second vibration detection sensor 8, and displays the result on the display means (not shown).

  As a result, the Coriolis mass flowmeter according to the present invention includes a vibration unit that resonates and vibrates the vibration tube in the secondary mode, a first vibration detection sensor that detects the amplitude of the vibration tube that resonates and vibrates in the secondary mode, A second vibration detection sensor for detecting the amplitude of the vertical vibration of the amplitude tube due to the Coriolis force, and an arithmetic control means for calculating the mass flow rate of the fluid to be measured based on the detection signal of the second vibration detection sensor; Adjusts the amplitude of vibration based on the detection signal from the first vibration detection sensor, so that the Coriolis force proportional to the mass flow rate can be measured by the vibration amplitude. Can be realized.

  That is, according to the present invention, since the Coriolis force proportional to the mass flow rate can be detected by the vibration amplitude by adopting the above-described configuration, it is “a few urad to several mrad or so, as in the conventional Coriolis mass flowmeter. This is effective in that a Coriolis flowmeter that is less susceptible to disturbance vibration and signal noise can be realized without requiring a phase difference calculation circuit that requires a large circuit scale and cost for measuring a “very small phase difference”.

  Further, the Coriolis mass flow meter according to the present invention is the same as the Coriolis mass flow meter according to the present invention in that the vibration means for resonating vibration of the vibration tube in the secondary mode and the amplitude of the vibration tube resonating in the secondary mode are used. Based on the detection signal of the first vibration detection sensor for detection, the second vibration detection sensor for detecting the amplitude of the vertical vibration of the amplitude tube due to the Coriolis force, and the detection signal of the second vibration detection sensor, the mass flow rate of the fluid to be measured is determined. Computation control means for calculating is provided, and the vibration means adjusts the amplitude of vibration based on the detection signal from the first vibration detection sensor, and the drive signal applied to the coil of the vibration means or detection by the second vibration detection sensor By providing a signal processing means for synchronously detecting the detection signal of the second vibration detection sensor using the signal as a reference signal, it is less susceptible to disturbance vibration and signal noise, and is low in cost. Possible to realize a small circuit scale Coriolis mass flowmeter.

  That is, according to the present invention, the Coriolis force proportional to the mass flow rate is measured by the vibration amplitude by the configuration as described above, and the vibration frequency by the Coriolis force is equal to the vibration frequency by the vibration means. Can be used to separate signal noise and disturbance vibration signals that are mixed in the vibration detection sensor with displacement due to Coriolis force, which is about 1/1000 smaller than the displacement caused by vibration, as in conventional Coriolis mass flowmeters. Therefore, it is effective in that a Coriolis flowmeter that is not easily affected by disturbance vibration and signal noise can be realized without requiring a filter circuit having a large circuit scale and cost burden for acquisition.

In the Coriolis mass flow meter according to the present invention, the shape of the vibration tube 1 is not limited to the U-shaped tube, and may be a straight tube shape as shown in FIG.
FIG. 3 is an explanatory view of the configuration of another embodiment of the Coriolis mass flow meter according to the present invention, and the same parts as those in FIG. In FIG. 3, the vibration tube 1 is formed in a straight tube shape. In the vibration tube 1, the vibration means 6, the first vibration detection sensor 7, and the second vibration detection sensor 8 are installed in this order along the direction of flow of the fluid to be measured.

DESCRIPTION OF SYMBOLS 20 Coriolis mass flowmeter 1 Vibrating tube 5 Base 6 Vibrating means 7 1st vibration detection sensor 8 2nd vibration detection sensor 9 Signal processing means

Claims (5)

A fluid to be measured is caused to flow through the vibrating tube, and the vibrating tube is deformed and vibrated by the flow and the Coriolis force generated by the angular vibration of the vibrating tube, and the vibration of the vibrating tube is detected by a vibration detection sensor. In the Coriolis mass flowmeter that measures the mass flow rate of the fluid to be measured flowing in the tube,
Vibration means for resonantly vibrating the vibration tube in a secondary mode;
A first vibration detection sensor that detects an amplitude of the vibration tube that resonates in a secondary mode;
A second vibration detection sensor for detecting the amplitude of vertical vibration of the amplitude tube due to Coriolis force;
Computation control means for calculating the mass flow rate of the fluid to be measured based on the detection signal of the second vibration detection sensor,
The Coriolis mass flowmeter, wherein the vibration means adjusts an amplitude of the vibration based on a detection signal from the second vibration detection sensor. The vibrating tube has a U shape,
The vibration means is disposed in one U-shaped straight tube portion of the vibration tube,
The first vibration detection sensor is disposed on the other U-shaped straight tube portion of the vibration tube,
2. The Coriolis mass flow meter according to claim 1, wherein the second vibration detection sensor is disposed in a U-shaped curved pipe portion of the vibration tube.   The said vibration means adjusts so that the amplitude of the resonant vibration of the secondary mode of the said vibration tube may be maintained to predetermined | prescribed amplitude based on the detection signal by the said 2nd vibration detection sensor. Coriolis type mass flow meter as described.   And a signal processing means for synchronously detecting the detection signal of the first vibration detection sensor using a drive signal applied to the coil of the vibration means or a detection signal from the second vibration detection sensor as a reference signal. The Coriolis type mass flowmeter according to any one of claims 1 to 3.   5. The Coriolis mass flowmeter according to claim 4, wherein the reference signal is substantially equal to a frequency of vertical vibration in the vicinity of the second vibration detection sensor.