JPH02280013A - Coriolis type mass flowmeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a mass flow rate needle, and in particular to a Coriolis mass flow rate needle configured to directly measure the mass flow rate of a fluid to be measured using the Coriolis force. Regarding the meter.

[Prior Art] As a mass flowmeter that directly measures the mass flow rate of a fluid to be measured, as shown in Japanese Patent Application Laid-Open No. 54-4168, a method is used to solve the Coriolis phenomenon that occurs when a fluid flows through a vibrating sensor tube. Mass flowmeters that measure mass flow using force are known. The structure of a mass flow meter using Coriolis is, for example, a pair of sensor tubes formed in a tJ shape with an inlet and an outlet, which are placed close to each other. !
There is a configuration in which the mass flow rate is obtained by vibrating in the direction related to It and detecting the displacement of the sensor tube due to Coriolis, which occurs in a magnitude proportional to the mass flow rate of the fluid to be measured passing through the pair of sensor tubes.

Here, the Coriolis force is in the opposite direction on the inlet side and the outlet side of the sensor tube, so it acts in a direction that twists the U-shaped tube of this sensor tube, and [the twist angle of the J-shaped tube is proportional to the mass flow rate]. do. To measure this twist angle, a pair of sensors are installed on the inlet and outlet sides of the sensor tube to detect the displacement of these sensor tubes, and the difference in time between the pair of sensors passing through the virtual zero point is calculated. A method of measuring is adopted.

The present applicant has proposed Japanese Patent Application No. 62-206984 as one of these measurement methods.

As shown in FIG. 12, this method uses the time difference between the detection signals el+82 output from the first and second position sensors to pass through a virtual zero point as the integration range, and the detection signals output from the first and second position sensors. el+8! The mass flow rate of the fluid flowing inside the sensor tube is measured by integrating the voltage difference between the two.

[Problems to be Solved by the Invention] As described above, in this method of measuring mass flow rate, the integration range is the time difference passing through the virtual zero point, and when noise occurs near the virtual zero point, the time difference due to this noise is The range of error will be included in the above integral range. Therefore, the range affected by noise (S+) is the integral range that should be measured (S2)
The problem is that the influence of this noise cannot be ignored in order to perform more accurate measurements.

[Means for Solving the Problems] In order to solve the above problems, the Coriolis mass flowmeter according to the present invention includes: a sensor tube having an inlet and an outlet, through which a fluid to be measured flows; a vibrator that vibrates a sensor tube; a first sensor that detects displacement on the inflow port side of the sensor tube; a second sensor that detects displacement on the outflow port side of the sensor tube; An upper limit value and a lower limit value are set within the amplitudes of two signals output by the first sensor and the second sensor, and the two signals output by the first sensor and the second sensor are set at the upper limit value. a slicer that regulates the signal value to the upper limit value when the signal value is higher than the lower limit value and regulates the signal value to the lower limit value when the signal value is lower than the lower limit value; an arithmetic circuit that calculates the difference between the signal of the second sensor and the signal of the second sensor; and an integrating circuit that integrates the signal output from the arithmetic circuit and outputs a signal proportional to the mass flow rate passing through the sensor tube. and .

[Function] By employing the above configuration, the Coriolis mass flowmeter of the present invention functions as follows.

The first and second sensors detect the displacement of the sensor tube that receives Coriolika due to the vibration of the vibrator, and the slicer shapes the difference between the two detection signals obtained by these sensors. An arithmetic circuit calculates the difference between the two detection signals, and an integrator circuit integrates the waveform obtained by the arithmetic circuit. Then, the mass flow rate of the fluid passing through the sensor tube is obtained from a signal value proportional to the mass flow rate integrated by this integrating circuit.

[First Embodiment] First, a measurement section of a Coriolis mass flowmeter which is an embodiment of the present invention will be described with reference to FIG. Figure 2 (A
), (B), and (C) show a perspective view, a plan view, and a side view of the measurement unit. In the figure, la is the flowmeter body of the mass flowmeter 1, and this flowmeter body 1a has holes at the upstream end and the downstream end through which the fluid to be measured passes (hereinafter, the holes formed on the upstream end side are inlet ports). 3. Let the hole formed on the downstream end side be the outlet 4.

) is provided, and has a flange portion 1h at the upstream end,
It has a flange portion 1c at the downstream end. In addition, this flange portion 1b is connected to the upstream piping (not shown).
c are respectively connected to upstream piping (not shown). In addition, the inlet side ends of a pair of sensor tubes (conduits) 2a and 2h formed by processing metal pipes into a U-shape are
The inflow port 3 and the outflow port side end of the flow meter main body 1a are connected to the outflow port 4, respectively. Sensor tube 2a.

2h, a permanent magnet 5a and a coil 6, which serve as the vibrator 5, are fixed to the sensor tube 2a and the sensor tube 2b so as to face each other.

7 and 8 are sensors that detect the displacement of the sensor tubes 2a and 2h, and since these sensors 7 and 8 have the same configuration, only one sensor 7 will be explained using FIG. 3, and the explanation of sensor 8 will be the same. Omitted. The sensor 7 has a coil portion 7 held by a holding member 9 fixed to the sensor tube 2a.
a, and permanent magnets 7b and 70 held by a holding member 10 fixed to the sensor tube 2b, and the coil portion 7a is arranged within the magnetic field of the permanent magnets 7b and 70. Therefore, the sensor tubes 2a and 2h are connected to the vibrator 5.
When excited and vibrated by (the permanent magnet 5a and the coil 6), the coil portion 7a provided in the sensor tube 2a will
It is displaced in the Z direction between permanent magnets 7b and 7c provided on the sensor tube 2b. Therefore, an electromotive force is generated in the coil portion 7a according to the relative speed of the sensor tubes 2a and 2b, and the sensor 7 detects the displacement of the sensor tubes 2a and 2b from the electromotive force generated by the coil portion 7a.

Here, as for the method of vibration, the permanent magnet 5a and the coil 6
are fixed to the sensor tube 2/l and the sensor tube 2b facing each other, so when the coil 6 is energized, the electromagnetic force acting between the coil 6 and the permanent magnet 5a causes the sensor tube 2a and the sensor tube 2b to separate. As shown in FIG. 2(C), they approach and separate in the Z direction. Sensor tube 2a
, 2b, the sensor tubes 2a and 2b vibrate facing each other like a tuning fork.

When the fluid to be measured flows inside the sensor tubes 2a and 2b,
Since the sensor tubes 2a and 2b vibrate, Coriolis occurs. The direction of this Coriolis is the direction of the vector product of the fluid movement direction and the vibration direction (angular velocity) that excites the sensor tubes 2a, 2b, and the magnitude of this Coriolis is determined by the direction of the turbid fluid flowing through the sensor tubes 2a, 2b. Proportional to mass and its speed.

A positive acceleration is applied to the fluid near the sensor 7 provided on the sensor tubes 2a, 2b on the inlet side, and a negative acceleration is applied to the fluid near the sensor 8. As a result, on the inlet side, the sensor tubes 2a, 2
Coriolika works to suppress the vibrations of the sensor tubes 2a and 2b, and on the outlet side, Coriolika works to accelerate the vibrations of the sensor tubes 2a and 2b. Therefore, when the fluid flows through the sensor tubes 2a, 2b, the sensor tubes 2a, 2h
Coriolis acts in the direction of twisting the 5-shaped part of A certain time difference r occurs between the output signal of the sensor 8 and the output signal of the sensor 8 installed on the outlet side. This time difference τ is proportional to the mass flow rate. Here, the sensors 7 and 8 detect the displacement of the sensor tubes 2a and 2b, respectively. They are output as detection signals to terminals 11 and 12 of the circuit shown in FIG. 1, respectively.

FIG. 1 shows a circuit diagram of an embodiment of the Coriolis mass flowmeter of the present invention, and this circuit diagram will be explained together with the waveform diagram shown in FIG. 4.

Detection signals output from sensors 7.8 are input to terminals 11.12, respectively, and these detection signals are input to amplifier 13.
．． 14, respectively. The detection signal e2 shown in FIG. 4(A) amplified by the amplifier 14 is output to a sample hold control circuit 23 and slicer 15, which will be described later, and the detection signal e2 shown in FIG. The signal e1 is output to a slicer 16, which will be described later. If the maximum limit voltage (upper limit value) of the slicer 15.16 where the detection signal e2+ el is manually input is vI, and the minimum limit voltage (lower limit value) is v2, then the slicer 15.16 has the voltage waveform of the detection signal e2+ el. The voltage of the portion that is greater than or equal to the maximum limit voltage vI is set to the maximum limit voltage V, and the voltage of the portion that is less than or equal to the minimum limit voltage v2 is set to the minimum limit voltage v2. However, the maximum voltage of the detection signal e1 is eImsx, the minimum voltage is elmin, and the maximum voltage of the detection signal e2 is 82
If the n□ minimum voltage is 82+sin, the following equation holds true.

V, >V.

elamX IeZmmX>vl eIm=n +82a+4,1<V2 Also, as an example of the slicer 15.
As shown in the figure, a comparator composed of comparators 17 and 1B, a resistor 19, and analog switches 20 and 21 is used. . Here, the slicer 15 and the slicer 16 have the same configuration, and the only difference is that the slicer 15 receives the detection signal et manually, whereas the slicer 16 receives the detection signal e.
Only the slicer 15 will be explained, and the explanation of the slicer 16 will be omitted.

Since the maximum limit voltage (upper limit value) v is supplied to the negative input of the comparator 17, the comparator 17
If the voltage of the detection signal e supplied to the positive input of is higher than the maximum limit voltage v1, the output is H (HIG
H). Since the minimum limit voltage (lower limit value) v2 is supplied to the positive input of the comparator 18, the detection signal e supplied to the negative input of the comparator 17
2 is lower than the minimum limit voltage v2, the output becomes H (HIGH). analog switch 20.21
is configured to short-circuit when an H signal is applied to the control terminal. Therefore, the detection signal itself is the maximum limit voltage ν1
When the analog switch 20 is short-circuited, the voltage of the detection signal e"2 outputted by the slicer 15 becomes the maximum limit voltage vI. Furthermore, when the detection signal fi= is lower than the minimum limit voltage V! , analog switch 21
is short-circuited, so the detection signal o output from the slicer 15
The voltage of 12 becomes the minimum limit voltage v2.

In other ranges, that is, when the voltage of the detection signal e2 is lower than the maximum limit voltage vI and higher than the minimum limit voltage v2, the detection signal e2 is passed through the resistor 19 to the detection signal e.
It is output as is as ′□. Therefore, the detection signal e2
The voltage waveform of is shaped by the slicer 15 into the voltage waveform of the detection signal e+2 shown in FIG. 4(C), and
The voltage waveform of the detection signal e1 is the detection signal e+ shown in FIG. 4(D) by the slicer 16.

The voltage waveforms are respectively shaped as follows. The slicer 15 and the slicer 16 then use this shaped detection signal e.
Outputs a voltage waveform of +2+fl'l.

The arithmetic circuit 22 has two input terminals, the positive input receives the detection signal e+2 from the slicer 15, and the negative input receives the detection signal e''1 from the slicer 16. A voltage waveform e representing the voltage difference between the signal e' and the signal e' (shown in FIG. 4(E)).
is output to an integrating circuit 30, which will be described later.

Sample and hold control circuit 231, for example,
Comparator 24.25°27 as shown in FIG.
．． 28 and AND circuits 26 and 29. The detection signal e! output from the amplifier 13 is connected to the positive input of the comparator 24! is input, and the maximum limit voltage (upper limit value) Vt [see FIG. 4(A)] is input to the negative input. Then, when the voltage of the detection signal et is higher than the maximum limit voltage vI, the comparator 24
Outputs H (HIGI()) to the D circuit 26.

The detection signal et output from the amplifier 14 is input to the positive input of the comparator 25, and the maximum limit voltage (upper limit value) vI is input to the negative input.

Then, when the voltage of the detection signal e2 is higher than the maximum limit voltage V, the comparator 25 sends an H signal to the AND circuit 26.
(IITGll) is output. The AND circuit 26 has two input terminals, one of which receives the signal output from the comparator 24, and the other input terminal receives the signal output from the comparator 25.

Then, the AND circuit 26 outputs an H signal to both of the two input terminals.
Only when (IIIGH) is input, <H(I(IGH)) is output as a clear signal e5 as shown in FIG. 4(G).

The detection signal e2 output from the amplifier 13 is input to the negative input of the comparator 27, and the positive input is
The minimum limit voltage V2 (see FIG. 4(A)) is input. Then, the comparator 27 outputs H(RIG)l when the voltage of the detection signal e2 is lower than the minimum limit voltage ν2.
) is output to the AND circuit 29. Also, comparator 2
The detection signal e outputted from the amplifier 13 is input to the negative input of 8, and the minimum limit voltage ■ is input to the positive input.
2 has been input. Then, the comparator 28 determines that the voltage of the detection signal e2 is the minimum limit voltage V! When it is lower than , as shown in Fig. 4 (H), AND
Output to circuit 29. The AND circuit 29 has two input terminals, and one of these input terminals is connected to the comparator 2.
The signal output by comparator 7 is input, and the other side is connected to comparator 2.
The signal output by 8 is input. And AND circuit 2
9, only when H()IIG) is input to the two input terminals, <H(old GH
) is output as a sample hold signal e6.

The integrating circuit 30 is composed of an operational amplifier 31, a resistor 32, an analog switch 33, and a capacitor 34.

Analog switch 33 is sample hold control circuit 23
It is short-circuited when the clear signal e outputted from the terminal is inputted, and is opened when it is not inputted. Therefore, the capacitor 34 connected in parallel to the analog switch 33 discharges when the clear signal e is input to the analog switch 33.

Therefore, the integrating circuit 30 integrates the voltage waveform output from the arithmetic circuit 22. At this time, since the polarity of the voltage waveform e outputted by the arithmetic circuit 22 is inverted every half cycle as shown in FIG. 4(E), the waveform of the integral signal e4 outputted by the integrating circuit 26 is It becomes a trapezoidal wave as shown in F). This integral signal e4 is output to the sample and hold circuit vs35.

The sample-and-hold circuit 35 holds the voltage value of the integral signal e4 inputted from the integrating circuit 3o when the sample-and-hold signal e outputted from the sample-and-hold circuit 23 described above is inputted, and also controls the voltage value. Output. The terminal 36 receives the voltage value output from the sample hold circuit 35, and outputs a voltage value proportional to the mass flow rate of the fluid passing through the sensor tubes 2a, 2b.

Here, if the detection signal output from the sensor 7 via the amplifier 13 is e, and the detection signal output from the sensor 8 via the amplifier 14 is 82, then el and e.

is expressed by the following formula.

e+=A1 sin(ωt) ez+=At sin [ω(t+r)] The voltage values of the above detection signals e1 and e2 are the maximum limit voltage (upper limit value)■, the lower limit voltage and the minimum limit voltage (lower limit value)■ When input to each slicer 15.16 that regulates 2 or more, the voltage waveform output from the slicer 15.16 is shown in Figure 4 (C).
, as shown in (D), become e+2 and e.

Then, the detection signal e 2+ output from the arithmetic circuit 22
When the differential voltage (e'2-e'I) of e+ is integrated by the integrating circuit 30 with an integration time constant of CR, the slicer 1
Integrating circuit 30 when 5 and slicer 16 are operating
As shown in FIG. 5, the voltage of the integral signal e4 outputted by
The value is the same as the area (shaded area in FIG. 5) surrounded by the maximum limit voltage vl, the minimum limit voltage Vt, and the detection signals e1 and e2.

Therefore, using the time when the voltage of the detection signal e becomes O as the reference (0 seconds), the time when the voltage of the detection signal e2 matches the maximum limit voltage ■1 is the time when the voltage of the detection signal e2 matches the minimum limit voltage v2. The time is t2, the time when the voltage of the detection signal el matches the minimum limit voltage Vl is t, the time when the voltage of the detection signal el matches the minimum limit voltage v2 is t, and the time constant of the integrating circuit 30 is CR (however, the time constant of the capacitor 31 is Capacitance C and resistance ml of resistor 28?
shall be. ), then the following formula holds.

CRet=(shi, -shit)(t<t+) S
ij (Le'+)dtS:? (e', -ν,)
dt = (V+Vt)(L L) −νr(ts
t3) ”VzCtt J) Jura 1e'IdL
S:? e'z dt-L(h t+) V
z(tn tz)-5ile'z dt+5 j?
e', dt. Here, if the relationship between the maximum limit voltage V and the minimum limit voltage V is V+ +Vt=0, then CRe1=V+(h t+ +t4tz).

Then, tz−F+ t4=i, +τ, 1. =1. +
Since τ, CRe1=V+r. maximum! Assuming that the lJ limit voltage, the capacitance C of the capacitor 31, and the resistance value R of the resistor 28 are constant, the time difference signal τ is as follows: τ=CRe3/2ν.

Hail to you.

As described above, the Coriolis mass flowmeter of the present invention has the 11th
As shown in the figure, the detection signals output by the first and second sensors are adjusted to the maximum limit voltage (upper limit value) and the minimum limit voltage (
The mass flow rate to be measured is determined by manually using a slicer that limits the lower limit value to delete detection signals outside the maximum limit voltage and minimum limit voltage ranges, and by integrating the voltage difference between the resulting detection signals. This is what we seek.

Therefore, when noise occurs,
The influence of errors due to noise when using the method according to 84 (hatched area S2 in Figure 12) is smaller than the influence (shaded area S2 in Figure 12).
The shaded area S3) in the figure makes it possible to perform more accurate measurements than the conventional Coriolis mass flowmeter.

Note that in this embodiment, the sensor tube 2a.

The sensor shown in FIG. 3 is used as a sensor for detecting the displacement of the sensor tube 2a.

It goes without saying that any sensor may be used as long as it can continuously detect the displacement of 2b.

[Second Embodiment] FIG. 8 shows a circuit of a second embodiment of the Coriolis mass flowmeter according to the present invention. While the first embodiment described above integrates only the falling portions of the two detection signals el+82 as shown in FIG. 10, the second embodiment integrates the two detection signals el+82 as shown in FIG. el+e! Both the rising and falling parts of the flow rate are integrated, and the mass flow rate can be calculated more accurately using the average value.

Note that parts having the same configuration as the Coriolis mass flowmeter of the first embodiment are denoted by the same numbers, and a description thereof will be omitted.

In FIG. 8, 22'' is an arithmetic circuit, and the arithmetic circuit 2
Of the two input terminals, the detection signal e''1 from the slicer 16 is input to the positive input terminal, and the detection signal e'2 from the slicer 15 is input to the negative input terminal, and this detection signal e11 and the detection signal e'2 are input to the negative input terminal. A voltage waveform representing the voltage difference with the signal e'2 (voltage waveform e shown in FIG. 4(F)) is shifted symmetrically around the 0 axis.

) is output to an integrating circuit 30'', which will be described later.

The integrating circuit 30' has the same circuit configuration as the integrating circuit 30 used in the first embodiment, and the difference is that the integrating circuit 30'
In this case, a clear signal es (shown in FIG. 4 (G)) is input to the analog switch 33, while a sample hold signal ebc is input to the analog switch 33'' (not shown) in the integrating circuit 30''. As shown in Figure 4 (1)).
is input as a clear signal. The analog switch 33' is short-circuited when the sample hold signal eb (clear signal) is input, and is opened when it is not input. For this reason, analog switch 3
A capacitor 34' (not shown) connected in parallel with 3'.

) performs discharge when the sample hold signal ea (clear signal) is input to the analog switch 33'. Therefore, the integrator circuit 30'' integrates the voltage waveform output from the arithmetic circuit 22'', and uses the resulting voltage value as the sample-and-hold circuit 3.
Output to 5°.

The sample and hold circuit 35'' has the same configuration as the sample and hold circuit 35 of the first embodiment, and the difference is that the sample and hold signal e6 is input to the sample and hold circuit 35, whereas the integration circuit 30'' clear signal e
, is input as a sample hold signal. Therefore, the sample hold circuit 35' holds the voltage value of the integral signal input from the integrating circuit 30'' when the clear signal es (sample hold signal) output from the sample hold control circuit 23 mentioned above is input. At the same time, the voltage value is output.The voltage value of this output signal is shown in the shaded area S in FIG.

is the same as the area value shown as , and the sensor tube (
Needless to say, it is proportional to the mass flow rate of the fluid passing through the pipes 2a and 2b.

50 is an arithmetic circuit having two input terminals and one output terminal. Of the two input terminals of the arithmetic circuit 50, a voltage value proportional to the mass flow rate of the fluid flowing in the sensor tubes 2a, 2b outputted from the sample hold circuit 35 is input to one, and the voltage value proportional to the mass flow rate of the fluid flowing in the sensor tubes 2a, 2b output from the sample hold circuit 35 is input to the other.
A voltage value proportional to the mass flow rate of the fluid flowing in the sensor tubes 2a and 2h outputted from the sensor tubes 5' is inputted.

Then, the arithmetic circuit 50 adds up the voltage values manually input to the two input terminals, divides the obtained value by 2, and calculates the average voltage value as the mass flow rate of the fluid flowing inside the sensor tubes 2a and 2h. terminal 36 as a proportional voltage value.
Output to.

Comparing the Coriolis mass flow needle of the second embodiment configured as described above with the first embodiment, the following effects are obtained.

As mentioned above, in the first embodiment, the measurement range is the shaded area shown in FIG. 10, whereas in the second embodiment, the measurement range is the shaded area shown in FIG. Therefore, in the second embodiment, since a measurement range twice the measurement range of the first embodiment is used to obtain the average value of the time difference τ, the influence of measurement errors due to noise is further alleviated. be done.

In addition, in this embodiment, the sensor tubes 2a and 2b are
Although a J-shaped one is used, the shape is not limited to this, and is shown, for example, in Japanese Patent Application No. 62-206985. It goes without saying that any shape may be used as long as Coriolis can be detected, such as a single character shape.

In addition, in this embodiment, the mass flow rate is measured using both the rising portion and the falling portion of the two detection signals el+82 as the integral range, but the mass flow rate is measured using only the falling portion as the integral range. may be measured.

[Effects of the Invention] As described above, the Coriolis mass flowmeter of the present invention converts the detection signals output by the first and second sensors to the maximum limiting voltage (
By inputting it into the slicer that limits the voltage to the maximum limit voltage (upper limit value) and the minimum limit voltage (lower limit value), the maximum limit voltage and minimum limit voltage Ii! The mass flow rate to be measured is determined by removing outside signals and integrating the voltage difference of the detection signals obtained thereby. Therefore, when noise occurs, the effect is less than the error caused by noise when applying the method disclosed in Japanese Patent Application No. 62-206984, so it is possible to achieve more accurate measurement than the conventional Coriolis mass flowmeter. It becomes possible.

[Brief explanation of drawings]

1 and 8 are circuit diagrams of the first and second embodiments of the Coriolis mass flowmeter of the present invention, and FIG. 2 (A). (B) and (C) are diagrams showing the main body of the Coriolis mass flow meter, Figure 3 is a configuration diagram of the sensor of the Coriolis mass flowmeter, and Figure 4 is a signal waveform diagram of each part of the circuit shown in Figure 1. FIG. 5 is a diagram showing the integral range of the detection signal of the Coriolis mass flow needle of the first embodiment, FIG. 6 is a circuit diagram of the slicer, and FIG.
The figure is a circuit diagram of the sample and hold control circuit, Figure 9.
Figures 10 and 11 are diagrams showing the measurement accuracy of the Coriolis mass flowmeter according to the present invention and the influence of Φ on noise, and Figure 12 is the measurement accuracy of the conventional Coriolis mass flowmeter. FIG. 2 is a diagram showing the degree of influence of noise on noise. Sensor tube 2a, 2b Exciter 5 Sensor...
・・・・・・・・・-7,8 slicer・・・・・・15.
16 Arithmetic circuit----22, 22' Sample hold control circuit----23 Integrating circuit----
------30.30' sample hold circuit...
・・−−−−−−35,35' calculation circuit・・・・・・・
...50 Agent Patent Attorney Setsuo Ninobe No. 5 Figure 'ii8 Figure 6 Figure Flute 12 Figure 6゜Drawing to be amended 7゜Contents of amendment Figures 11 and 12 will be amended as shown in the attached sheet. Written amendment to the above procedure (method) Display of the case 1999 Patent Application No. 101354 2゜Name of the invention Coriolis mass flowmeter 3゜Relationship with the case

Claims (1)

[Scope of Claims] A sensor tube having an inlet and an outlet, through which a fluid to be measured flows, an exciter for vibrating the sensor tube, and detecting displacement of the sensor tube on the inlet side. a first sensor; a second sensor that detects displacement on the outlet side of the sensor tube; and an upper limit and a lower limit within the amplitude of the two signals output by the first sensor and the second sensor. When the value is set and the two signals output by the first sensor and the second sensor have signal values higher than the upper limit value, the signal value is regulated to the upper limit value and a signal lower than the lower limit value. a slicer that regulates the signal value to the lower limit value when the signal value is at the lower limit value; an arithmetic circuit that calculates the difference between the signal of the first sensor and the signal of the second sensor that are output via the slicer; A Coriolis mass flowmeter comprising: an integrating circuit that integrates an output signal and outputs a signal proportional to the mass flow rate passing through the sensor tube.