JP2977130B1 - Mass flow meter flow conversion method and flow conversion device - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To correct a flow value of a mass flowmeter with a moving zero point value. SOLUTION: A measuring tube through which a fluid flows is vibrated, and a signal having a phase difference proportional to Coriolis force acting on the measuring tube is obtained from sensors 1 and 1 '.
The signal component is processed at 3 'to remove noise components, alternately switched by the S / C switching section 4, the comparator 5 converts the signal into a phase difference pulse signal, and the CPU 6 converts the Coriolis force into a flow rate value. When there is no flow rate by a command from the CPU 6,
That is, the control circuit 2 is on (SW1: on, SW2: off)
When the flow rate is present, that is, when the control circuit 2 is off (SW1: off, SW2: on), the moving zero value from the zero value is obtained, and the measured value of the mass flow meter is calculated by the moving zero value. to correct. Reliability can be secured in a mass flow meter with a wide rage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate conversion method and a flow rate conversion device for a mass flow meter, and more particularly, to a flow rate conversion method for a mass flow meter for correcting a flow rate value of a mass flow meter with a moving zero point value. The present invention relates to a flow conversion device.

[0002]

2. Description of the Related Art A Coriolis flowmeter supports a measuring tube through which a fluid to be measured flows at both ends, and when the central portion of the supported measuring tube is driven alternately in a direction perpendicular to a support line, both ends of the measuring tube are supported. This is a direct type flow meter that detects a phase difference signal proportional to the Coriolis force at a symmetric position between a part and a center part and obtains a mass flow rate proportional to the Coriolis force.

If the driving frequency of the alternating driving of the measuring tube is made equal to the natural frequency of the measuring tube, a constant driving frequency corresponding to the density of the measuring tube and the fluid to be measured can be obtained. It becomes possible. The phase difference signal is an amount proportional to the mass flow rate, but when the driving frequency is fixed, the phase difference signal can be detected as a time difference signal at the observation position of the measuring tube. This phase difference signal is
Theoretically, it is zero when the flow rate is zero, but in reality it does not become zero because there is noise based on temperature, vibration, etc.
And fluctuate.

In such a Coriolis flowmeter, SN
In order to improve the ratio, a straight-cross control method has been developed (for example, Japanese Patent No. 2583011,
JP-A-8-219842).

FIG. 4 is an overall circuit diagram of a conventional mass flow meter converter. In FIG.
3 'is an analog signal processing circuit, 4 is a switching control switching unit (hereinafter, referred to as S / C switching unit), 5 is a comparator, and 6 is a central processing unit (hereinafter, referred to as CPU).

Hereinafter, the mode of signal processing will be described.
5, 'the circuit diagram of the sensor coil 1, 1' conventional analog signal processing circuit 3, 3 an approximate sine wave input from the amplifier 7 and the linear amplification by the ratio of resistors R ₁ and R ₂ through a resistor R _3, to input to the integration circuit of the time constant determined by input to the inverting terminal P ₁ resistor R ₃ and capacitor C ₁ of the amplifier 8. The output P ₂ of the integration circuit contains low-frequency noise, which is low-pass filtered by a low-pass filter including a resistor R ₅ and a capacitor C _2, and subjected to impedance conversion by an amplifier 9. The low frequency noise output from the amplifier 9 further includes a resistor R
₆ through, and outputs the input to the inverting input P ₃ resistor R _6, low-frequency noise component which is integrated output with integrated by the integration circuit consisting of the capacitor C ₃ of the amplifier 10 to P _4. Low frequency noise signals of the phase difference signal with opposite phase that includes a low frequency noise signal component to be input to the inverting input P ₁ of the amplifier 8 is a non-inverting input, a sine wave signal A of the low-frequency noise is substantially zero output P ₂
(A ') is output.

FIG. 6 is a block diagram of a conventional S / C switching unit for switching the output of the analog signal processing circuit 3. The S / C switching unit 4 is composed of a switching circuit switched by a rectangular wave signal. If the wave signal is high, contact 1
1 and 12 are closed, and the contacts 13 and 14 are opened, so that points A and B and points A 'and B' are connected. Conversely, when the square wave signal is at a low level, the contacts 11 and 12 are opened and the contacts 13 and 14 are closed.
The point and the point A 'and the point B are connected, and the analog signal processing circuits 3, 3'
Are input to a comparator 5 described later. The noise of the circuit units at the preceding and subsequent stages is equivalently affected by the switching unit at the center of the S / C switching unit 4.

[0008] Figure 7 is a circuit diagram of a conventional comparator 5, the sine wave signal input through the S / C switching section 4, an amplification factor determined by the ratio of the resistor R ₈ and R _7, saturated The signal is converted to a trapezoidal wave signal via the amplifier 15 for amplification, and the resistance R
Input to the inverting input of the amplifier 16 via ₁₀ . Amplifier 1
The non-inverting input of 6, for example, a positive reference voltage is connected to the (not shown) resistor R ₁₁ and R ₁₂ and de-divided reference voltage is applied trapezoidal wave signal positive peak value (+ E) Further, a negative peak value (−E) is determined by a comparator (not shown), and a trapezoidal wave signal having peak values of (+ E) and (−E) is obtained.

FIG. 8 is a time chart for explaining a manner of obtaining (T + ΔT) and (T−ΔT) pulses from the trapezoidal wave signal having the phase difference obtained in FIG. 8A is a trapezoidal wave signal obtained by the comparator 5, and includes a trapezoid ABCD (solid line) and a trapezoid A. FIG.
₁ B ₁ C ₁ D ₁ ... (Dotted line) show displacement signals of measuring tubes having different voltages and having a voltage of which the peak of the absolute value of the voltage is equal (± E) with respect to the time axis XX. Each displacement signal is a trapezoidal trapezoidal waveform that is continuous on the time axis. The reference time representing the phase difference is the peak value C (+ E) or D (−E) of one trapezoidal waveform ABCD, for example, the hypotenuse CD. The time between the position and the position O crossing the time axis is represented by T.

On the other hand, the reference time of the trapezoidal waveform A ₁ B ₁ C ₁ D ₁ is the position O ₁ crossing the time axis. In the displacement signals of the trapezoid ABCD and A ₁ B ₁ C ₁ D _{1 having} different phases,
For example, a phase difference signal on the side CD and the side C ₁ D ₁ will be described. The quadrilateral CC ₁ D ₁ D is a parallelogram, the time difference ΔT between the parallel side CD and C ₁ D ₁ is a phase difference signal, and the sides CC ₁ and D ₁ D have a length equal to the time axis O · O _1. Have, point C
Assuming that the projection points from ₁ and D1 to the time axis are O ₂ and O ₃ , respectively, the side O ₂ O is time (T−ΔT), and the side OO ₃ is time (T +
ΔT). In the period of one cycle M shown in FIG. 8B, two pulses of the (T-.DELTA.T) pulse shown in FIG. 8C and the (T + .DELTA.T) pulse shown in FIG. ,
Output to C.

The CPU 6 shown in FIG. 4 is an arithmetic processing unit which receives an output from the comparator 5 and has at least a reference power source (not shown) and two charge / discharge circuits therein. The time difference of 4nΔT times is obtained by the method.

In this way, the analog signal processing circuits 3, 3 'remove the noise contained in the input signal and remove the drift component, and then the analog signal processing circuits 3, 3' by the S / C switching unit 4. ′ Are switched to further cancel errors included in the digital conversion circuit of the comparator 5.

[0013]

In recent years, there has been a demand for the development of a Coriolis flowmeter using such a control method and having a range of several times larger than the conventional range of 1:50 or 1: 100 or 1: 200. However, there is a problem that it is difficult to suppress the zero point fluctuation, and the reliability as a flowmeter is impaired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances. By correcting the actual flow value of a mass flow meter with a moving zero point value, a flow rate which can be reliably obtained in a mass flow meter having a wide range of renewability is obtained. A conversion method and a flow rate conversion device are provided.

[0015]

According to a first aspect of the present invention, a measuring tube through which a fluid flows is vibrated, and a signal having a phase difference proportional to the Coriolis force acting on the measuring tube is obtained by a pair of sensors. Each of the signals is processed by analog signal processing to remove noise components, and the signals are switched between straight and cross, input and converted into a phase difference pulse signal, and the phase difference pulse signal is processed to process the Coriolis force. In the flow rate conversion method of the mass flow meter, the component of the phase error shift of the sensor is Tshift, and the error component generated in the process of processing the analog signal is Toff, and the zero point of the mass flow meter when there is no flow rate. When the value Tzero is Tzero = Tshift +
A procedure for obtaining Toff, a procedure for obtaining a moving total value Toffze of an error caused by a plurality of samplings immediately after obtaining the zero point value and a flow rate is present, and a method for sequentially updating the moving total value at fixed time intervals. Moving average value Toff '
And a procedure for determining the zero value Tzerox as a function of the ratio between the moving average value Toff ′ and the moving sum value Toffze, where Tzerox is a zero value when there is a flow rate, Therefore, even if there are fluctuation elements such as electric drift in the circuit components and circuits of the mass flow meter, the zero point is corrected in real time during flow measurement, so accurate flow measurement can be performed even if environmental conditions such as temperature fluctuate. It is intended to increase the reliability of a mass flowmeter which can be performed and has a wide range capability.

According to a second aspect of the present invention, there is provided a pair of sensors for vibrating a measuring tube through which a fluid flows and transmitting a signal having a phase difference proportional to the Coriolis force acting on the measuring tube, and a signal from the sensor. Analog signal processing means for removing the noise component by analog signal processing, switching means for switching the signal from the analog signal processing means between straight and cross, and outputting the signal, and converting the signal inputted through the switching means A flow rate conversion device for a mass flow meter having a conversion means for converting the phase difference pulse signal from the conversion means and a central processing means for converting the Coriolis force into a flow rate by processing the phase difference pulse signal from the conversion means; A control means comprising a first switch disposed across the input of the signal processing means and a second switch disposed in series with the output of one of the pair of sensors. When the control means is turned on, the first switch is turned on, the second switch is turned off, and when the control means is turned off, the control means is controlled by the command signal from the central processing means. The central processing unit operates so that the switch is on and the first switch is off. The central processing unit is configured to control the phase error component of the sensor when the control circuit is off and the switching unit when the control circuit is on. The error component of the signal at the previous stage is obtained, the component of the zero point of the mass flow meter is obtained from the difference therebetween, and when there is a flow rate, the control means is turned on a plurality of times immediately after the component of the zero point is obtained. The moving sum of the error component of the signal at the previous stage of the switching means is obtained, the control means is sequentially turned on at regular intervals, the moving sum is updated and the moving average is obtained, and the moving sum and the moving sum are obtained. Moving average It is characterized in that the zero value corrected by the above is obtained, so that even if there is a variable element such as an electric drift in the circuit components and the circuit of the mass flow meter, the zero point is corrected in real time during the flow rate measurement and the environment such as temperature is corrected. The present invention is intended to provide a mass flow meter which performs accurate flow measurement even if the conditions fluctuate and which has a wide range of reliability and has high reliability.

According to a third aspect of the present invention, in the second aspect of the present invention, when the control means is turned on, the first control means outputs the first control signal.
Wherein the second switch is turned on first, the second switch is turned off later, and when the control means is turned off, the second switch is turned on first, and the first switch is turned off later, Thus, the zero point correction and the flow rate measurement can be performed stably without interrupting the current to the subsequent circuit section.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall circuit diagram for explaining an embodiment of a mass flow meter according to the present invention.
ALF (Calibration Flag) control circuit, SW ₁ is the sensor 1 side circuit and the sensor 1 'changeover switch provided across the side circuit, SW ₂ sensor 1' is a changeover switch provided in series. The same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. FIG. 2A shows the CAL of the present invention.
FIG. 3 is a configuration diagram of an F control circuit, in which IC1 is a D-latch, IC
2 is a one-shot multi. FIG. 2B is an explanatory diagram of the ON / OFF operation by the CALF control circuit of the present invention.

In FIGS. 1 and 2, the operation of the CALF control circuit 2 is performed by a command signal from the CPU 6. Therefore, the CPU 6 performs the same operation as that of FIG. 4 and issues a command signal to the CALF control circuit 2.

In FIG. 2A, when a command signal (pulse signal) is input from the CPU 6 to the CALF control circuit 2, SW ₁ is turned on (closed) and SW ₂ is turned off at the rise.
F (open), that is, the CALF control circuit 2 is in an ON state (at the time of ON), and at the time of its fall, SW ₁ is OFF.
(Open), SW ₂ is ON (closed), i.e. CALF control circuit 2 becomes the state of OFF (when OFF). These states can be revealed by a well-known D-latch IC ₁ , one-shot multi IC _2, or the like. FIG. 2 (B)
, A command signal (CALF signal) from the CPU 6
Is a pulse signal having a pulse width of 500 ms, for example.
When command signal is input, SW ₁ is turned on at the rise
(Closed), and keep ON (closed) until the pulse width (500 ms) is reached, and then turn OFF (open).
SW ₂ is turned off slightly after the rise of the command signal
(Open) and turns on (closed) with the fall of the command signal. Thus CALF control circuit 2, a state ON, the turned when connecting the output of the sensor 1 in both the subsequent circuit 3 and 3 ', previously the SW _1, after the SW _2, also the state of OFF Te, when connecting the subsequent circuit in the sensor 1, 1 ', previously the SW _2, and operates as later SW _1, is operated without interrupting the current to a subsequent circuit portion.

As a result, the input to the analog signal processing circuits 3 and 3 'is not cut off in time series, and therefore, the input to the integration circuit of the analog signal processing circuits 3 and 3'. A stable signal can be supplied to the resistance, and zero point check and flow rate measurement can be performed in real time.

[0022] In the present embodiment, changeover switch, wherein it is a 2 point of the SW ₁ and SW _2, the sensor 1 (LP
O) it can be a similar process be added as SW ₃ to the side.

Next, as one embodiment of the present invention, zero point correction in the case where two time phase sensor units are provided will be described. When there is no CALF, the time phase difference at the time of normal measurement is as follows. Here, Ta and Tb are noise components included in the subsequent stage of the S / C switching unit 4, Tc and Td are noise components included in the preceding stage of the S / C switching unit 4, and (d / dt ·
(T + n) and (d / dt · Tn) are the errors of each sensor. If the signal component elements included in the measured values are defined as follows, the input time difference to the CPU 6 is as follows: LPO and RPO on the left and right sensor units, respectively. dt · T + n) + Tc + Ta + nΔT (1) (for RPO) TRPO = T + (d / dt · T−n) + Td + Tb + nΔT (2) ΔT: At an arbitrary flow rate , And the phase difference between the left and right sides. In the straight control, the time phase difference of the above two equations is calculated by d / dt · (T + n−T−n) + (Tc−Td) + (Ta−Tb) + by the calculation of the equations (1)-(2). 2nΔT (3) Since Ta and Tb are interchanged during the cross control, d / dt · (T + n−T−n) + (Tc−Td) is calculated by the equation (1) − (2). + (Tb−Ta) + 2nΔT (4) Therefore, when the straight control and the cross control are continuously and alternately performed, the equations (3) and (4) are added, and d / dt · 2 (T + n−T−n) +2 (Tc−Td) + 4nΔT (5) This equation is the sum of the total noise relating to the circuit and the time phase difference held from the beginning of both the left and right signals, that is, basically the error of the circuit and the sensor. Then, since this error causes a change in the zero point, if the value of each component element forming this error is known, it is possible to correct the zero point conversely.

When the CALF control circuit 2 is turned on with no fluid flowing through the mass flow meter for zero point correction, that is, when the flow rate is zero, T + n = T-n and 4nΔT = 0. If this value is Toff, the expression (5) is as follows: Toff = 2 (Tc-Td) (6) This expression represents the noise included in the circuit at the preceding stage of the S / C switching unit 4. Therefore, the initial zero value Tzero of the mass flow meter is the sum of the noise Toff of the circuit at the preceding stage of the S / C switching unit 4 and the deviation (difference) of the phase error of the sensors 1 and 1 'in the above state, If this is expressed by an equation, Tzero =
Toff + d / dt · (T + n−T−n). Here, if d / dt · (T + n−T−n) = Tshift, then Tzero = Toff + Tshift (7) The Toff sets the CALF control circuit 2 to, for example, 3
By turning ON twice, the Tof obtained by sampling
Calculate as the average of f data.

Therefore, if Toff and Tshift are obtained, Tzero
Is determined, for example, when the temperature changes, correction may be made based on this. For this reason, immediately after the zero determination,
That is, immediately after obtaining Toff and Tshift, the CALF control circuit 2 is turned on at a certain interval, for example, 32 times in a state where there is a flow rate.
Then, 32 pieces of Toff data are obtained and averaged to obtain a moving total value Toffze. This moving sum value Toffze
Is determined immediately after the determination of the zero point, and is hardly affected by the temperature of the fluid. Therefore, it is a reference when there is a flow rate. The moving sum value Toffze
Starts to be affected by temperature and the like as time elapses after the flow measurement starts after the fluid starts flowing. Therefore, after starting the flow of the fluid, a command signal is issued from the CPU 6 at regular intervals (flag is raised) and the CALF control circuit 2 is turned on.
The moving average value Toff 'is obtained by sequentially updating the moving sum value with the latest Toff obtained by turning on the CALF control circuit 2 as Toff by sampling.

When the moving average value Toff 'is obtained in this manner, assuming that Toff affected by the temperature is Toffx, Toffx = Toff × {[(Toff'-Toffze) / Toffze] +1} (8) Becomes

On the other hand, Tshift is similarly affected by temperature. If Tshift affected by temperature is Tshiftx, assuming that Tshiftx = (Toffze / Toff ') × Tshift (9), (9) Tzerox = (Toffze / Toff ′) × Tshift + (Toffze / Toff ′) × Toff (10) This is the corrected zero value by adding equations (8) and (9) from equation (7). If the measured value of the flow rate is corrected with this zero point value, an accurate measured value can be obtained. Of course, if Tshiftx in equation (9) is constant, then Tzerox = Tshift + (Toffze / Toff ′) × Toff (10) ′.

FIG. 3 is a time chart for explaining the procedure for correcting the zero point according to the present invention, and the algorithm shown in the above equation will be described with reference to the time chart. (A) With the mass flow meter having no flow rate and the CALF control circuit 2 being turned off, a component Tzero of the sensor phase error is obtained (FIG. 3A). (B) For this purpose, the S / C switching unit is sampled by turning the CALF control circuit 2 ON, for example, 32 times by a command signal from the CPU 6 in a state where the mass flow meter has no measurement and the CALF control circuit 2 is ON. The noise Toff included in the circuit at the preceding stage of No. 4 is obtained (FIG. 3A). (C) The phase error component Tzero of the sensor and the S / C
The noise Toff included in the circuit at the preceding stage of the switching unit 4 is determined by the CPU.
6 to obtain the zero point value Tshift of the mass flow meter. (D) Immediately after the zero point value is obtained, the mass flow meter is caused to flow into a fluid to be in a measurement state, and CA is determined by a command signal from the CPU 6.
By sampling the LF control circuit 2 to be turned on 32 times, a moving total value Toffze of the noise Toff included in the circuit at the preceding stage of the S / C switching unit 4 is obtained (FIG. 3B). (E) After obtaining the moving sum, after a certain period of time, the CPU
6 turns on the CALF control circuit 2 in response to a command signal,
The moving average value Toff ′ is obtained by replacing the Toff data (n ₁ ) obtained by the previous sampling of the moving sum value with the latest Toff data (n ₃₃ ) obtained by turning on the CALF control circuit 2. Thereafter, the movement total value is updated in the same manner every predetermined time (FIG. 3B). (F) The phase error component Tshift of the sensor and the S /
The noise Toff included in the circuit at the preceding stage of the C switching unit 4 is corrected by the moving sum value Toffze and the moving average value Toff ′ to obtain a zero point value Tzerox.

[0029]

According to the first aspect of the present invention, a measuring pipe through which a fluid flows is vibrated, and a signal having a phase difference proportional to the Coriolis force acting on the measuring pipe is obtained by a pair of sensors. Analog signal processing to convert the signal into a phase difference pulse signal by switching between straight and cross, converting the signal into a phase difference pulse signal, and processing the phase difference pulse signal to convert the Coriolis force into a flow rate In the flow rate conversion method for a mass flow meter, when a component of a shift of the phase error of the sensor is T shift and an error component generated in a process of performing the analog signal processing is T off, a zero point value T zero of the mass flow meter when there is no flow rate. Tzero = Tshift + Toff, and a procedure immediately after obtaining the zero point value and calculating a moving total value Toffze of errors caused by a plurality of samplings when there is a flow rate. And a procedure for sequentially updating the moving sum value at fixed time intervals to obtain a moving average value Toff ', and when a zero point value when there is a flow rate is Tzerox, the zero point value Tzerox is referred to as the moving average value Toff'. And a procedure for obtaining the value as a function of the ratio of the moving sum value Toffze, so that the circuit for processing a phase difference signal from the sensor converts electrical drift of the constituent electronic components due to electrical noise or temperature change and the signal. Even if there is a variable element such as electrical drift in each circuit to be processed, the zero point is corrected in real time during flow measurement, so accurate flow measurement can be performed even if environmental conditions such as temperature fluctuate. In addition, the reliability can be improved in a mass flowmeter having a wide range of renewability.

According to the second aspect of the present invention, a pair of sensors for exciting a measuring tube through which a fluid flows and transmitting a signal having a phase difference proportional to the Coriolis force acting on the measuring tube, and Analog signal processing means for removing the noise component by performing analog signal processing on each of the signals, switching means for switching the signal from the analog signal processing means between straight and cross, and outputting the signal, and the signal inputted through the switching means. A conversion means for converting a signal into a phase difference pulse signal, and a flow rate conversion device of a mass flow meter having a central processing means for processing the phase difference pulse signal from the conversion means to convert the Coriolis force into a flow rate. A control comprising a first switch disposed across an input of the analog signal processing means and a second switch disposed in series with an output of one of the pair of sensors. A step, wherein the control means is configured such that, when the control means is on, the first switch is on, the second switch is off, and the control means is off when the control means is off, according to a command signal from the central processing unit. The second switch is turned on, the first switch is turned off, and the central processing unit operates when the control circuit is off, and the phase error component of the sensor and the control circuit are on when the control circuit is on. The error component of the signal at the previous stage of the switching means is obtained, the component of the zero point of the mass flow meter is obtained from the difference therebetween, and when there is a flow rate, immediately after the component of the zero point is obtained, the control means is executed. A plurality of times are turned on to obtain a moving sum value of an error component of a signal at a preceding stage of the switching means, and the control means is sequentially turned on at regular intervals to update the moving sum value to obtain a moving average value. Value and move Since the zero point value corrected by the average value is obtained, the electric noise of the constituent electronic parts due to electric noise or temperature change generated in the circuit for processing the phase difference signal from the sensor and the respective circuits for converting and processing the signal Even if there is a variable element such as electric drift in the flow rate, the zero point is corrected in real time during the flow rate measurement, so that accurate flow rate measurement can be performed even if environmental conditions such as temperature fluctuate, and rangeability is improved. A highly reliable flowmeter can be provided in a mass flowmeter having a large width.

According to the third aspect of the present invention, in addition to the effect of the second aspect of the present invention, when the control means is on, the first switch is turned on first and the second switch is turned on. Later, when the control means is off, the second switch is turned on first, and the first switch is turned off later, so that the current to the subsequent circuit section can be stably set without interrupting the current to the subsequent stage. Correction and flow measurement can be performed.

[Brief description of the drawings]

FIG. 1 is an overall circuit configuration diagram for explaining an embodiment of a mass flow meter according to the present invention.

FIG. 2 is a diagram illustrating the configuration and operation of a CALF control circuit according to the present invention.

FIG. 3 is a diagram for explaining a procedure for correcting a zero point according to the present invention.

FIG. 4 is an overall circuit diagram of a conventional mass flow meter converter.

FIG. 5 is a circuit diagram of a conventional analog signal processing circuit.

FIG. 6 is a configuration diagram of a conventional switching control switching unit.

FIG. 7 is a circuit configuration diagram of a conventional comparator.

FIG. 8 is a time chart showing a conventional mode for obtaining a time phase difference signal.

[Explanation of symbols]

1, 1 '... sensor coil, 2 ... CALF control circuit, 3,
3 ': analog signal processing circuit, 4: switching control switching section, 5: comparator, 6: central processing unit (CPU), 7, 8, 9, 10 ... amplifier, 11, 1
2, 13, 14 ... contact, 15, 16 ... amplifier, IC ₁ ...
D latch, IC ₂ ... one shot multi.

Claims (3)

(57) [Claims] 1. A measuring tube through which a fluid flows is vibrated, a signal having a phase difference proportional to the Coriolis force acting on the measuring tube is obtained by a pair of sensors, and analog signals are processed to remove noise components. The signal is converted to a phase difference pulse signal by switching the signal between straight and cross,
In the flow rate conversion method for a mass flow meter that processes the phase difference pulse signal to convert the Coriolis force into a flow rate, a component of a phase error shift of the sensor is Tshift, and an error component generated in the process of processing the analog signal is Tshift. When Toff is set, the zero point value Tzero of the mass flow meter is set to T when there is no flow rate.
a procedure for obtaining zero = Tshift + Toff, a procedure for obtaining a moving total value Toffze of an error caused by a plurality of samplings immediately after obtaining the zero point value when there is a flow rate, and sequentially calculating the moving total value at fixed time intervals. A procedure for obtaining a moving average value Toff 'by updating, and a procedure for obtaining the zero point value Tzerox as a function of the ratio of the moving average value Toff' to the moving sum value Toffze when a zero value when there is a flow rate is Tzerox. A flow rate conversion method for a mass flow meter, comprising: 2. A pair of sensors for exciting a measuring tube through which a fluid flows and transmitting a signal having a phase difference proportional to the Coriolis force acting on the measuring tube, and processing analog signals from the sensors. Analog signal processing means for removing noise components, switching means for switching the signal from the analog signal processing means between straight and cross, and outputting the signal, and converting the signal input through the switching means into a phase difference pulse signal. A mass flowmeter having a conversion means for converting, and a central processing means for processing the phase difference pulse signal from the conversion means to convert the Coriolis force into a flow rate; And a control unit including a second switch disposed in series with an output of one of the pair of sensors, the control unit comprising: The first switch is turned on when the control means is on, the second switch is off when the control means is on, and the second switch is on when the control means is off by the command signal from the central processing means. 1 is turned off, and the central processing means comprises: a component of a phase error shift of the sensor when the control circuit is off; and an error component of a signal preceding the switching means when the control circuit is on. To determine the zero-point component of the mass flow meter from the difference between them, and when there is a flow rate, immediately after obtaining the zero-point component, the control means is turned on a plurality of times and the switching means The moving sum value of the error component of the signal at the previous stage is obtained, the control means is sequentially turned on at regular intervals, the moving sum value is updated, the moving average value is obtained, and the moving average value is corrected by the moving sum value and the moving average value. Zero Flow rate conversion apparatus of the mass flowmeter and obtains the value. 3. The control means, wherein when the control means is on, the first switch is turned on first, the second switch is turned off later, and when the control means is off, the second switch is turned on first. 3. The mass flow meter according to claim 2, wherein the first switch is turned off later.