JP2007263859A - Vibration type measurement device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove fluctuations in a phase difference signal caused by the torsional vibration of a sensor tube. <P>SOLUTION: A flow measurement control circuit 40 comprises a filtering circuit 54 for outputting only AC components changing for each period of a measured phase difference signal, an amplitude change measurement circuit 60, and a filter constant change circuit 62, in which the amplitude change measurement circuit 60 determines the torsional vibrations of the sensor tubes 14, 15 caused by external vibration from the magnitude of the signals and the frequency of the filtering circuit 54, and the filter constant change circuit 62 changes a signal process condition so as to attenuate the torsional vibrations. With the above, even when the balance of the sensor tubes 14, 15 is changed by a temperature and then behaviors (amplitude and frequency) are changed, the phase difference signal unaffected by the torsional vibrations can be obtained and thereby a high pressure fluid can be measured precisely. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vibration type measurement apparatus, and more particularly to a vibration type measurement apparatus configured to detect a displacement corresponding to a Coriolis force acting on a sensor tube by vibrating the sensor tube.

  For example, a Coriolis mass flow meter or a vibratory density meter is available as a vibratory measuring device that measures a physical quantity of a fluid by vibrating a pipeline supplied with the fluid. Hereinafter, the Coriolis type mass flow meter will be described. In this Coriolis type mass flow meter, a sensor tube through which a fluid to be measured passes is vibrated in a tube diameter direction by a vibrator, and a displacement of the sensor tube due to a Coriolis force proportional to the flow rate is detected by a pickup. Further, the vibration type density meter has the same configuration as the Coriolis type mass flow meter, and the sensor tube vibrates at a frequency corresponding to the density of the fluid to be measured.

  A conventional Coriolis mass flowmeter is configured to flow a fluid through a pair of sensor tubes and vibrate the pair of sensor tubes in a direction approaching and separating from each other by a driving force of a vibrator (drive coil) (for example, , See Patent Document 1). Conventionally, the exciter and the pickup coil are composed of a magnet and a coil. When a drive pulse or an alternating voltage (AC signal) with positive and negative is input to the drive coil of the exciter, it is attached to the sensor tube. The sensor tube is vibrated by applying an attractive force or a repulsive force to the drive magnet, and the displacement of the detection magnet attached to the vibrating sensor tube is detected from the sensor coil (detector) of the pickup. It is detected by a signal.

  The Coriolis force acts in the vibration direction of the sensor tube and is in the opposite direction between the inflow side and the outflow side of the sensor tube. Therefore, the sensor tube is twisted due to Coriolis force, and the twist angle is proportional to the mass flow rate of the fluid flowing in the sensor tube. Therefore, a pair of pickups (vibration sensors combining a coil and a magnet) for detecting displacement due to vibration and Coriolis force are provided at the twisting positions on the inflow side and the outflow side of the pair of sensor tubes. The mass flow rate is measured by measuring the phase difference (time difference) between the output detection signals of both sensors.

  However, when the Coriolis mass flow meter is provided in the gas supply path for supplying a gas pressurized to a high pressure such as CNG or hydrogen used as a fuel for automobiles, the pressure resistance of the sensor tube is reduced. Need to increase.

  However, if the thickness of the sensor tube is increased, the driving force of the vibrator that vibrates the sensor tube must be increased, and the sensor tube is increased in rigidity, and the deformation of the sensor tube due to the Coriolis force is reduced. As a result, the phase angle (twist angle) of the vibration sensors on the inlet side and the outlet side becomes small, which causes a decrease in measurement accuracy.

Therefore, in the conventional Coriolis type mass flow meter, the distance between the inlet side and the outlet side of the sensor tube is shortened or the length of the sensor tube is increased to increase the twist, that is, the phase angle due to the Coriolis force. It is being considered.
JP-A-6-331406

  However, in a Coriolis mass flow meter, increasing the detection sensitivity of a Coriolis force by picking up means that the sensor tube is weakened against vibrations from the outside. For example, the entire sensor tube is Coriolis. It may vibrate in the same direction as the force, causing a phenomenon that decays over a long time.

  For this reason, in the conventional one, a zero cut circuit for controlling the flow rate adjustment valve based on a detection signal different from the true flow rate of the sensor tube or for preventing the signal from being output when the flow rate is zero. Will operate and output a value different from the actual flow rate, which may reduce the flow control and measurement accuracy.

  Further, the variation for each cycle of the signal detected by the pickup becomes zero when averaged for a long time, but when the variation for each cycle is large, the time for averaging to the required accuracy becomes longer. Problems arise.

  Therefore, in view of the above circumstances, an object of the present invention is to provide a vibration type measuring apparatus that solves the above-described problems.

  In order to solve the above problems, the present invention has the following means.

  The invention according to claim 1 includes a sensor tube through which a fluid to be measured flows, a vibrator for vibrating the sensor tube, an inflow side pickup for detecting an inflow side displacement of the sensor tube, and an outflow side of the sensor tube. An oscillating type having an outflow side pickup for detecting displacement, and a phase difference measuring means for measuring a phase difference between a first detection signal obtained from the inflow side pickup and a second detection signal obtained from the outflow side pickup. In the measurement apparatus, a vibration state measurement unit that measures whether or not the vibration state of the sensor tube has changed due to a disturbance other than the Coriolis force acting on the sensor tube based on the change in the phase difference signal, and the sensor tube includes: When there is a vibration component due to disturbance other than the Coriolis force, the phase difference signal is processed according to the vibration frequency at that time. A signal processing changing means for further comprises solves the serial problems.

  When the sensor tube periodically changes due to disturbances other than the Coriolis force, the signal processing changing unit preferably calculates an average value corresponding to the period and corrects the phase difference signal.

  The signal processing changing means includes a fluctuation period detecting means for detecting a period when the sensor tube periodically fluctuates due to a disturbance other than the Coriolis force, and a fluctuation period detected by the fluctuation period detecting means. And calculating means for calculating the averaging time by changing the filter constant.

  According to the present invention, when the sensor tube has a vibration component due to a disturbance other than the Coriolis force, the processing of the phase difference signal is changed according to the vibration frequency at that time. Thus, even when gas pressurized at a high pressure can be measured with high sensitivity, it is possible to eliminate errors in the phase difference signal due to periodic fluctuations in the sensor tube due to torsional vibration (disturbance). Therefore, when measuring the flow rate of the high-pressure gas having a relatively small specific gravity, it is possible to accurately measure even if torsional vibration occurs in the sensor tube due to an action other than the Coriolis force.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a front view of a Coriolis mass flow meter as an embodiment of a vibration type measuring apparatus according to the present invention. FIG. 2 is a side view of the Coriolis mass flow meter shown in FIG. The vibration type measuring device can be used as a vibration type density meter and a Coriolis type mass flow meter because the mass flow rate can be obtained using the density and density of the fluid to be measured. Since the vibration type density meter and the Coriolis type mass flow meter have the same configuration, this embodiment will be described in detail when used as a mass flow meter.

  As shown in FIGS. 1 and 2, the mass flow meter 10 includes a manifold 12, inverted U-shaped sensor tubes 14, 15 connected to the upper surface of the manifold 12 and formed in parallel, A vibration exciter 16 attached between 15 arcuate intermediate portions 14c, 15c, an inflow-side vibration pickup 18 for detecting the inflow-side relative displacement (relative speed) between the sensor tubes 14 and 15, and the sensor tube 14 And an outflow side vibration pickup 20 for detecting the relative displacement (relative speed) on the outflow side between the first and second components. The manifold 12 is made of, for example, a rectangular parallelepiped metal block, and has an inlet 12a at one end and an outlet 12b at the other end. The inflow side end portions 14a and 15a of the sensor tubes 14 and 15 are communicated with the inflow port 12a, and the outflow side end portions 14b and 15b of the sensor tubes 14 and 15 are communicated with the outflow port 12b. Therefore, the fluid that has flowed into the inflow port 12a passes through the sensor tubes 14 and 15 and flows out to the outside through the outflow port 12b.

  The vibration exciter 16 includes an excitation coil 16 a attached to the tip of the sensor tube 14 and a magnet 16 b attached to the tip of the sensor tube 15. The vibration pickup 18 includes a sensor coil 18 a attached to the vibrating sensor tube 14 and a magnet 18 b attached to the sensor tube 15. The vibration pickup 20 includes a sensor coil 20 a attached to the sensor tube 14 and a magnet 20 b attached to the sensor tube 15.

  A temperature sensor 30 is provided for measuring the temperature on the inflow side of the sensor tubes 14 and 15 or in the vicinity of the inlet 12 a of the manifold 12.

  As shown in FIG. 1, the vibrator 16, the inflow-side vibration pickup 18, and the outflow-side vibration pickup 20 are symmetrical with respect to the vertical line crossing the intermediate position of the sensor tubes 14 and 15 as viewed from the front, and The inflow side vibration pickup 18 and the outflow side vibration pickup 20 are provided symmetrically with respect to the center. The vibrator 16 is driven and controlled by the flow rate measurement control circuit 40, and detection signals detected by the inflow side vibration pickup 18 and the outflow side vibration pickup 20 are input to the flow rate measurement control circuit 40.

  The exciter 16 is configured so that the magnet 16b attracts or repels a magnetic field generated by applying a positive and negative alternating voltage (AC signal) to the excitation coil 16a, thereby moving the intermediate portion of the sensor tube 14 in the lateral direction (Y direction). ). Naturally, the same force acts on the sensor tube 15 as the reaction force, and the sensor tube 15 vibrates in the opposite direction.

  Since the inflow-side vibration pickup 18 is composed of the coil 18a and the magnet 18b, the coil 18a and the magnet 18b come close to and away from the sensor tube 14 and the sensor tube 15 on the inflow side. A detection signal corresponding to the displacement amount (displacement speed) of the coil 18a and the magnet 18b is output. Further, since the outflow side pickup 20 is composed of the coil 20a and the magnet 20b, the coil 20a and the magnet 20b come close to and away from the sensor tube 14 and the sensor tube 15 on the outflow side. A detection signal corresponding to the displacement amount (displacement speed) of the sensor coil 20a and the magnet 20b is output.

  FIG. 3 is a block diagram showing the flow rate measurement control circuit 40 of the mass flow meter 10. As shown in FIG. 3, the flow measurement control circuit 40 includes an intrinsically safe explosion-proof barrier circuit 42, an excitation circuit 44, an amplitude detection / excitation / phase difference (time difference) detection circuit (hereinafter referred to as “phase difference detection circuit”) 46, and Have Furthermore, it has a barrier circuit 32 to which a temperature signal detected by the temperature sensor 30 is inputted, a temperature measurement circuit 34, and a Young's modulus calculation circuit 36.

  The flow rate measurement control circuit 40 also includes a variable gain amplifier 50 that corrects the phase difference (time difference) signal output from the phase difference detection circuit 46 based on the temperature correction value input from the Young's modulus calculation circuit 36, and the Young's modulus. A flow rate output circuit 52 that performs V / F conversion and outputs a flow rate pulse, and a filtering circuit 54 that averages the phase difference signal in accordance with the phase difference fluctuation period. Further, the flow measurement control circuit 40 averages the amplitude change measurement circuit (vibration state measuring means) 60 for measuring the amplitude change of the phase difference signal, and the torsional vibration frequency and the torsional vibration amplitude output from the amplitude change measurement circuit 60. And a filter constant changing circuit (signal processing changing means) 62 for calculating the time (fluctuation period) and changing the filter constant.

  The filter constant changing circuit 62 obtains the period when the sensor tubes 14 and 15 periodically fluctuate due to disturbances other than the Coriolis force (fluctuation period detecting means), changes the filter constant, and averages according to the fluctuation period. The calculation time is calculated (calculation means). The filtering circuit 54 averages the time difference signal based on the filter constant output from the filter constant changing circuit 62.

  In the mass flow meter 10 having the above-described configuration, the vibrator 16 is driven by the flow measurement control circuit 40 during flow rate measurement, and the sensor tube has a period and amplitude according to the vibration characteristics (natural frequency) of the sensor tubes 14 and 15. The intermediate portions 14c and 15c of 14 and 15 are vibrated. The sensor tubes 14 and 15 vibrate in the proximity and separation directions (Y direction, see FIG. 2) with the arc-shaped intermediate portions 14c and 15c using the both ends fixed to the manifold 12 as fulcrums.

  At this time, when a fluid flows through the vibrating sensor tubes 14 and 15, a Coriolis force having a magnitude corresponding to the flow rate is generated. Therefore, an operation delay occurs between the inflow side and the outflow side of the sensor tube 14, thereby causing a phase difference between the sensor signal of the inflow side pickup 18 and the sensor signal of the outflow side pickup 20.

  Since the phase difference between the inflow side sensor signal and the outflow side sensor signal is proportional to the flow rate, the flow rate measurement control circuit 40 calculates the flow rate based on the phase difference. Therefore, when the displacement of the sensor tube 14 is detected by the inflow side pickup 18 and the outflow side pickup 20, the phase difference accompanying the vibration of the sensor tube 14 is converted into a mass flow rate by the flow rate measurement control circuit 40.

  For example, when the mass flow meter 10 is provided in a hydrogen dispenser to perform high-pressure hydrogen flow measurement and filling control, the sensor tubes 14 and 15 are vibrated to generate a Coriolis force proportional to the mass flow rate on the inflow side vibration waveform and the outflow side. Measure from the difference from the vibration waveform. With the thickness of the sensor tubes 14 and 15 that can withstand high-pressure hydrogen, the generated time difference is small, resulting in a phase difference (time difference) that cannot be measured with the current size or length. Therefore, the sensor tubes 14 and 15 are easily twisted by increasing the length of the sensor tubes 14 and 15 or by making the interval between the connection portions with the manifold 12 smaller than the interval between the vibration pickup mounting positions, thereby increasing the phase difference. It will be necessary. However, increasing the sensitivity to the Coriolis force means that it becomes weaker against external vibrations, and the entire sensor tube vibrates in the same direction as the Coriolis force and decays over a long period of time. The phenomenon is seen.

  Therefore, in addition to the phase difference (DC component: flow rate) due to Coriolis force, a phenomenon may occur in which vibrations such as the sensor tubes 14 and 15 remain twisted due to external vibrations (disturbances). In this case, the flow rate is controlled based on a signal different from the true flow rate, and when the flow rate is zero, a zero cut circuit for outputting a flow rate pulse is activated, resulting in a value different from the actual flow rate. Will be output. Further, the variation of the flow rate signal for each cycle becomes zero when averaged for a long time, but when the variation is large, the time for averaging to the required accuracy becomes long.

  Therefore, in this embodiment, when the variation of the phase difference signal (time difference signal) for each cycle (difference from the moving average or the filtered value) is large, the sensor tubes 14 and 15 are twisted in addition to the excitation mode. Is provided with an amplitude change measuring circuit 60 as means for judging that vibration is abnormal and a filter constant changing circuit 62 and a filtering circuit 54 as control circuits for suppressing the vibration.

  Here, the principle in the case of measuring the flow rate of the fluid to be measured by vibrating the sensor tube 14 with the vibrator 15 will be described with reference to FIGS. FIG. 4 is a diagram schematically showing a state in which the vibrator 15 vibrates the sensor tube 14. FIG. 5 is a diagram schematically showing the Coriolis force acting on the vibrating sensor tube 14.

  As shown in FIG. 4, during flow rate measurement, positive and negative alternating voltages (AC signals) are alternately output from the excitation circuit 44 of the flow rate measurement control circuit 40 to the excitation coil 16 a of the vibrator 16. As a result, forces in the opposite direction with the same value are generated in the excitation coil 16a and the magnet 16b installed in the sensor tube 15, so that the intermediate portion of the sensor tubes 14 and 15 and the sensor tube 15 vibrate in a resonance state.

  As shown in FIG. 5, reverse Coriolis forces + F and −F act on the inflow side and the outflow side of the sensor tube 14. Thereby, the sensor tubes 14 and 15 have a phase difference in vibration between the inflow side and the outflow side.

  That is, when the intermediate portion 14c of the sensor tube 14 is driven as shown by a one-dot chain line in FIG. 4, a Coriolis force + F acts on the inflow side of the sensor tube 14 as shown by a broken line in FIG. Coriolis force -F acts on the outflow side. Further, when the sensor tube 14 is driven as indicated by a broken line in FIG. 4, the Coriolis force −F acts on the inflow side of the sensor tube 14 as indicated by the solid line in FIG. Force + F acts.

The displacement of the sensor tube 14 is detected by the sensor coils 18a and 20a of the vibration pickups 18 and 20, and a signal having a phase difference (time difference) Δt from the excitation signal input to the vibrator 16 in the flow measurement control circuit 40. And further converted into a flow rate pulse. That is, the flow rate measurement control circuit 40 calculates the mass flow rate Qm by using the following equation.
Qm = A · Δt (1)
However, in the formula (1), A is a constant specific to the mass flow meter.

  Further, the Coriolis force acts at the same frequency as the vibration frequency of the sensor tube 14. However, the torsional vibration of the sensor tube 14 caused by external noise such as noise and vibration has a frequency different from the vibration frequency of the sensor tube 14. For this reason, when the phase difference (time difference) Δt is detected, a phenomenon occurs in which the time difference increases or decreases every cycle.

  In the flow rate measurement control circuit 40 shown in FIG. 3, the phase difference signal with respect to the Coriolis force is a DC component, and the torsional vibration is observed as an AC component. Therefore, a filtering circuit 54, an amplitude change measuring circuit 60, and a filter constant changing circuit 62 that output only an AC component that changes for each cycle of the measured phase difference signal are provided, and the amplitude change measuring circuit 60 outputs the signal of the filtering circuit 54. The torsional vibration of the sensor tubes 14 and 15 due to external vibration is obtained from the magnitude and frequency, and the signal processing conditions are changed by the filter constant changing circuit 62 so as to attenuate the torsional vibration.

  Thereby, even if the balance of the sensor tubes 14 and 15 changes with temperature and the behavior (amplitude and frequency) of the torsion signal changes, a phase difference signal that is not affected by torsional vibration can be obtained. (For example, hydrogen, CNG, etc.) can be measured. In addition, even when the response frequency and the time constant are set according to the application such as the flow rate control, the flow measurement control circuit 40 is affected by the frequency of the torsional vibration by the filtering circuit 54, the amplitude change measurement circuit 60, and the filter constant change circuit 62. Therefore, high-pressure fluid can be measured with high accuracy.

  Here, the phase difference due to the waveform of the sensor signals of the vibration pickups 18 and 20 will be described with reference to FIGS. Moreover, in FIG. 6, FIG. 7, it is experimental data at the time of measuring a fixed flow volume, and a fixed Coriolis force has generate | occur | produced. Here, the phase difference Δt at the center of the sine wave (sensor signal is 0 volt) is measured.

  6A and 6B are waveform diagrams of sensor signals of the vibration pickups 18 and 20, respectively. As shown in FIG. 6A, the phase difference Δt between the inflow side sensor signal S1 (indicated by a solid line) and the outflow side sensor signal S2 (indicated by a broken line) is a time difference caused by the Coriolis force, As shown in FIG. 6B, if the flow rate is constant over time, the flow rate is constant.

  FIGS. 7A and 7B are waveform diagrams of sensor signals of the vibration pickups 18 and 20 detected when other vibrations such as torsional vibration are generated in the sensor tubes 14 and 15. As shown in FIG. 7A, the phase difference Δt between the inflow side sensor signal S1 (indicated by a solid line) and the outflow side sensor signal S2 (indicated by a broken line) is positive in the A region, It changes to almost zero in the region and returns to positive in the C region. In normal flow measurement, when the flow rate changes, the phase difference Δt increases or decreases in proportion to the flow rate change.

  However, when other vibrations such as torsional vibration (disturbance) occur in the sensor tubes 14 and 15, a phenomenon occurs in which the phase difference Δt increases or decreases rapidly or decreases to zero even though there is a flow rate. For example, as shown in FIG. 7B, when the phase difference Δt in the region B decreases to zero, it is possible to determine that torsional vibration due to disturbance has occurred in the sensor tubes 14 and 15.

  Further, in the sensor signal waveform shown in FIG. 7A, the sensor signal S1 of the vibration pickup 18 and the sensor signal S2 of the vibration pickup 20 have an interval in the time axis direction, that is, a phase difference (time difference). As shown in FIG. 7B, it can be seen that the measurement result (phase difference between the sensor signals S1 and S2) of the phase difference Δt varies (changes in a stepped manner) every cycle.

  Since the fluctuation (variation) in the phase difference Δt occurs periodically, it is considered that the sensor tubes 14 and 15 are caused by torsional vibration. When torsional vibration occurs in the sensor tubes 14 and 15, the phase is advanced on the one side and the phase is delayed on the other side of the sensor tubes 14 and 15, so that the phase difference between the inflow side and the outflow side occurs. If the difference from the average value is taken, it is torsional vibration itself.

  Therefore, the flow rate measurement control circuit 40 obtains the frequency and amplitude of the torsional vibration from the phase difference signal by using the circuit configuration shown in FIG. 3, and calculates to remove the disturbance component due to the torsional vibration. That is, in the flow measurement control circuit 40, the DC component (this is a time difference due to Coriolis force) included in the phase difference signal from the output of the phase difference detection circuit 46 and the AC component (the sensor tubes 14 and 15 are twisted) included in the phase difference signal. Signal) is separated by the amplitude change measurement circuit 60 to detect torsional vibration of the sensor tubes 14 and 15, and the flow rate signal is moved by the filtering circuit 54 or the filter constant changing circuit 62 according to the signal. The flow rate signal is generated by changing the constant of the circuit to be averaged.

  FIG. 8 to FIG. 10 show graph I (broken line) changes in the phase difference signal when torsional vibration (disturbance) is applied in a state where fluid flows through the sensor tubes 14 and 15. In the state where this constant flow rate is measured, the phase difference signal moves up and down (fluctuates in the increase / decrease direction) about once every four cycles due to, for example, torsional vibration of the sensor tubes 14 and 15. In addition, when the sensor tubes 14 and 15 of the present embodiment are used, it can be seen from the experimental data that there are phase difference signal components having a period n times 4 periods.

Here, looking at changes in the time difference signal when the filtering process and the moving average process are performed by the filtering circuit 54, the graph II of the filter process when the time constant is fixed (see FIG. 8) and the moving average with the fixed average time. In the processing graph III (see FIG. 9), it can be seen that a component having a frequency of one quarter of one cycle remains. (The average time in FIG. 9 corresponds to 10 cycles.)
In this embodiment, since the torsional vibration of the sensor tubes 14 and 15 occurs once every four periods, the moving average process is changed so that the average time of one multiple of the four periods becomes the average time. As shown in the graph IV of FIG. 10, the variation in the phase difference is reduced, it is reduced to about ½ compared to the average time fixed, and the fluctuation of the phase difference signal is about 1 compared to the filter processing. It can be seen that it decreases to / 3.

  Thus, by performing the averaging process of the phase difference signal according to the period of the torsional vibration generated in the sensor tubes 14 and 15, the variation in the phase difference due to the torsional vibration can be reduced. Measurement accuracy can be further improved. In particular, when measuring the mass flow rate of a high-pressure gas such as hydrogen or CNG having a relatively small specific gravity, the rigidity and support strength of the sensor tubes 14 and 15 may be lowered in order to increase measurement sensitivity. When such rigidity and support strength of the sensor tubes 14 and 15 are lowered, there is a possibility that torsional vibration may occur in the sensor tubes 14 and 15 as described above. However, in the flow rate measurement control circuit 40 as in this embodiment, the phase difference due to the Coriolis force included in the phase difference signal from the output of the phase difference detection circuit 46 and the signal component in which the sensor tubes 14 and 15 are twisted and vibrated. Is separated by the amplitude change measurement circuit 60, and the torsional vibration of the sensor tubes 14 and 15 is detected, and the constant of the circuit for moving and averaging the flow rate signal by the filtering circuit 54 or the filter constant changing circuit 62 is changed according to the signal. Thus, in order to generate the flow rate signal, a phase difference signal from which signal components due to torsional vibrations are removed is obtained, and flow rate measurement accuracy is ensured.

  In the above embodiment, the case where the sensor tubes 14 and 15 are formed in an inverted U shape has been described as an example. However, the present invention is not limited to this, and other shapes (for example, straight tube, inflow side end portion) Of course, it may be an Ω shape in which the distance between the end portion and the outflow side end portion is narrow, or a shape bent in a J shape.

  Moreover, in the said Example, although hydrogen and CNG were illustrated as a high pressure fluid to be measured, it cannot be overemphasized that it is applicable also when measuring high pressure gas other than this.

It is a front view of a Coriolis type mass flow meter as one example of a vibration type measuring device according to the present invention. It is a side view of the Coriolis type mass flow meter shown in FIG. 3 is a block diagram showing a flow rate measurement control circuit 40 of the mass flow meter 10. FIG. It is a figure which shows typically the state which the vibrator 15 vibrates the sensor tube. It is a figure which shows typically the Coriolis force which acts on the sensor tube 14 to vibrate. It is a wave form diagram of a sensor signal of vibration pickups 18 and 20. It is a wave form diagram of a sensor signal of vibration pickups 18 and 20 detected when other vibration, for example, torsional vibration occurs in sensor tubes 14 and 15. It is a wave form diagram which shows graph II which performed the graph I and the filter process which performed the change of the phase difference signal when torsional vibration (disturbance) is added. It is a wave form diagram which shows the graph III which performed the graph I and the moving average process about the change of the phase difference signal when torsional vibration (disturbance) is added. It is a wave form diagram which shows the graph IV which performed the graph I and the moving average process about the change of the phase difference signal when a torsional vibration (disturbance) is added.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mass flow meter 12 Manifold 14, 15 Sensor tube 16 Exciter 18 Inflow side vibration pickup 20 Outflow side vibration pickup 30 Temperature sensor 34 Temperature measurement circuit 36 Young's modulus calculation circuit 40 Flow measurement control circuit 44 Excitation circuit 46 Amplitude detection / excitation Phase difference detection circuit 50 Gain variable amplifier 52 Flow rate output circuit 54 Filtering circuit 60 Amplitude change measuring circuit 62 Filter constant changing circuit

Claims (3)

A sensor tube through which the fluid to be measured flows;
A vibrator for vibrating the sensor tube;
An inflow side pickup for detecting an inflow side displacement of the sensor tube;
An outflow side pickup for detecting outflow side displacement of the sensor tube;
In a vibration type measuring apparatus having a phase difference measuring means for measuring a phase difference between a first detection signal obtained from the inflow side pickup and a second detection signal obtained from the outflow side pickup,
Vibration state measuring means for measuring whether or not the vibration state of the sensor tube has changed due to a disturbance other than the Coriolis force acting on the sensor tube based on the change of the phase difference signal;
When the sensor tube has a vibration component due to disturbances other than the Coriolis force, signal processing changing means for changing the processing of the phase difference signal according to the vibration frequency at that time;
A vibration type measuring apparatus characterized by comprising:   2. The signal processing changing unit corrects the phase difference signal by calculating an average value corresponding to the period when the sensor tube periodically varies due to disturbances other than the Coriolis force. The vibration-type measuring device described in 1. The signal processing changing means includes
When the sensor tube periodically fluctuates due to disturbances other than the Coriolis force, fluctuation period detecting means for obtaining the period;
A calculation means for calculating the averaging time by changing the filter constant according to the fluctuation period detected by the fluctuation period detection means;
The vibration type measuring apparatus according to claim 2, wherein

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