JPS6396517A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To realize a mass flowmeter whose temperature characteristic is satisfactory, by installing a resistance thermometer bulb in the vicinity of a stress detecting sensor, and compensating a temperature characteristic of a piezoelectric constant, etc., of a piezoelectric element by its output. CONSTITUTION:Eddy signals from the first and the second stress detecting sensors 142, 141 are brought to a signal conversion by an adding-subtracting circuit 33, and inputted to an F/V converter 41 through a filter circuit 37, the first amplifying circuit 38, and a Schmitt circuit 39. On the other hand, an output of the adding-subtracting circuit 33 is inputted to a dividing circuit 42 through a temperature compensating circuit 51, the second amplifying circuit 34, a detecting circuit 35, and a rectifying circuit 36, divided by an output signal of the F/V converter 41, and becomes an electric signal corresponding to a mass flow. Also, a temperature compensation based on a piezoelectric constant of a piezoelectric element, a temperature expansion of a force receiving body and a duct line, and a temperature change of bending rigidity of the outside cylindrical part and the inside cylindrical part is executed by an output of a resistance thermometer bulb 511.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mass flow meter that measures the mass flow rate of a measurement fluid using Karman vortices.

(Prior Art) It has been known for a long time that when an object is placed in a fluid, vortices are generated alternately and regularly from the side surface of the object, and the fluid flows downstream in the form of a vortex train. This vortex street is called a Karman vortex street, and the number of vortices generated per unit time (generation frequency) is proportional to the flow rate of the fluid.

Therefore, a vortex generator is placed in the pipe that guides the fluid to be measured, and the vortex generator generates a vortex proportional to the flow velocity.The change in lift caused by the vortex is measured using sensors such as piezoelectric elements, strain gauges, capacitance, and inductance. Vortex flowmeters have been put into practical use that measure the flow velocity and flow rate of fluid by detecting and extracting only the frequency of the detection signal. Incidentally, the flow rate that one generally wants to know is often the mass flow rate, not only in processes that involve chemical changes, but also in transactions. Furthermore, when the measured fluid is gas or steam, its density changes greatly depending on temperature and pressure, and even when it is a liquid, its density changes considerably at 11 degrees. For this reason, the mass flow rate is measured by installing it in parallel with a vortex flow meter to measure humidity and pressure, or by measuring the density with a densitometer. However, using a density meter and a vortex flowmeter is complicated and expensive, and using a combination of a temperature or pressure gauge and a vortex flowmeter is not only complicated and expensive, but also requires accuracy and response because it is difficult to measure the temperature of the fluid. Sex is also bad.

By the way, as shown in FIG. 9, when the vortex generator 2 is arranged in the conduit 1 and the measurement fluid is flowed through the conduit 1, the average drag force F acting on the vortex generator 2 is: , fluctuating lift FL and pressure loss Δ
P has a relationship with one loss as shown by the following equation.

F-=j: C engineering pV2 (2) L LQ However, CD: Anti-puff coefficient CL; Fluctuation lift coefficient Cp: Pressure loss coefficient ρ; Density V: Flow velocity (1) and (2), for example, see “Flow Studies Vol. Chapter Vortex P, 79. P, 8721 Kutajyukovsky's Theorem Written by Tanibetsu, Iwanami Shoten. Moreover, (3) is derived from the loss due to separation of the boundary layer from the vortex generator (generation of Karman vortices).

Now, the average drag force FP, the variable lift force F, and the pressure loss J loss ΔP are the drag coefficient CD, the variable lift coefficient C5, and the pressure loss coefficient Cp.
If is a constant, it is proportional to ρ■2, so the eddy frequency (3)
By dividing the equation, we get ρ■. Drag coefficient C.

Regarding the variable lift coefficient CL and pressure loss coefficient cpO values,
For example, the drag coefficient CI) is determined for each mallet-shaped vortex generating body, as shown in FIG.

Also, by dividing ρ■2 detector and V detector, ρ
・For determining the IA flow rate of V2/V-ρ■, as described in Flow Measurement Handbook P, 344, written by Hirobu Yoda, published by Nikkan Kogyo Shimbun, there is a technique that has been commonly used in the past. It is.

In the case of a vortex flowmeter, a known example of this fence is the West German patent DE3032578C2r "Method and apparatus for dynamically density-independent determination of the measured fluid (measuring mass flow rate using a vortex flowmeter)". The fluctuating lift force can be detected as distortion in a strain gauge attached to the vortex generator, the torque generated in the vortex generator by a spring can be detected, or a pitot tube can be installed in front of the 7fiI generator to detect the drag force. By dividing by the frequency, F! ! There is one that calculates the iEN flow rate.

In addition, in Japan, Utility Model Application Publication No. 54-174359 “
In the "Measurement device using Karman vortices", a capacitance measuring section using a diaphragm is installed upstream and downstream of the vortex generating body.
Some methods calculate the mass flow rate by detecting and dividing the drag force F0 from the DC component of the capacitance change and the vortex frequency from the AC component.

Further, Japanese Patent Application Laid-Open No. 57-61916 "Measuring Device Using Karman Vortex" shows an example of detecting the fluctuating lift force and dividing it by the vortex frequency.

JP-A-57-61916 will be explained below.

FIG. 1 is an explanatory diagram of the structure of this patent publication No. 57-61916. In the figure, 1a is a pipe through which the measurement fluid flows, 2a
is a columnar vortex generator inserted perpendicularly into the pipe line 1a, and its both ends are fixed to the pipe line 1a. The main body 21a of the vortex generator 2a is made of stainless steel or the like, and has a cross-sectional shape, such as a trapezoid, that does not produce a Karman vortex street in the measured fluid and stably enhances lift changes.

The top 22a of the vortex generator 2a is made of stainless steel or the like, has a recess 23a, and is integrally formed with the main body 21a by i8 contact or the like. 41a is an element body consisting of a piezoelectric element;
It is sealed to the recess 23a of the vortex generator 2a with an insulating material 3a such as glass, and is formed integrally with the vortex generator. Further, the element main body 41a has a disk shape. Furthermore, the element body 41a is divided symmetrically into left and right sides on the front and back, respectively, as shown in Figs.
2a, 43a, 44. a, 45a are provided, the portion sandwiched between electrodes 42a and 43a forms a first piezoelectric sensor 45a, and the portion sandwiched between electrodes 44a and 45a forms a second rE electric sensor 47a. Then, the electrodes 42a and 45a and the electrode 43a are arranged so that the charges generated in the first and second piezoelectric sensors 46a and 47a are differential.
and 44a are connected to each other, and lead wires 48a and 49a are taken out from the electrodes 42a and 44a, respectively, through the insulating material 3a. 8a is a detection signal processing circuit, which detects the AC; load q detected by the piezoelectric sensors 46a and 47a;
Convert to AC voltage e. 9a is a ratio meter, which measures AC voltage e
This is for converting the signal into a pulse signal P of a constant level. IOa is an F/V converter that converts the pulse signal P of the comparator output into a DC voltage E1 proportional to its frequency. Ila is a rectification and smoothing circuit that rectifies and smoothes the AC voltage e.
It is converted into a direct current voltage E2 proportional to its amplitude.

12a is an arithmetic circuit which outputs outputs E1. This is to perform a desired calculation on E2 and extract a signal related to the density or mass flow rate of the fluid from its output.

In the present invention configured in this manner, when the measuring fluid flows into the pipe line 1a, the vortex generator 2a generates a Karman vortex and receives a lift change based on the generation of the vortex. When the vortex generating body 2a receives a change in lift, a stress change in the opposite direction is generated inside the vortex generating body 2a across the neutral axis as shown in the figure. This stress change occurring in the vortex generator 2a is transmitted to the element body 41a which is integrally attached to the vortex generator 2a through an insulating material 3a. Therefore, the first. In the second piezoelectric sensors 46a and 47a, changes in the amount of charge that are in opposite phases to each other occur in response to changes in lift force. The amount of electric charge generated in the piezoelectric sensors 46a and 47a is extracted differentially, and an alternating electric charge q is generated between the lead wires 48a and 49a. The alternating charge q is converted into an alternating voltage e by the detection signal processing circuit 8a. If the frequency of the AC voltage e is taken out via the comparator 9a and the F/V converter IOa, the high frequency E1 - K+V as in the general vortex flow meter is obtained as shown in equation (4).
(4) However, K1 is a proportional constant. On the other hand, if the amplitude of the AC voltage e is extracted through the rectifying and smoothing circuit 11a, the output E2 of the rectifying and smoothing circuit 11a is given by the following equation, where ρ is the density of the fluid.

K2− K2 ρy 2 (5
) However, K2 is a proportionality constant, and its output EO is as follows. If the cross-sectional area of the conduit 1a is S, the cooling amount Qm is given by: Qm ρV S (7) Therefore, Eo is as follows, which is a signal proportional to the mass flow rate.

Furthermore, if the arithmetic circuit 12a squares E and then divides E2, the output Eo can be obtained as follows.

(Problems to be Solved by the Invention) However, since such a device uses a piezoelectric element, when there is a temperature change, the detection accuracy deteriorates significantly due to the influence of the temperature coefficient of the piezoelectric element. In addition, there is also a shadow C of the thermal expansion of the vortex generator 2a and the thermal expansion of the pipe line 1a.
Based on temperature characteristics (accuracy becomes stone).

In vortex flowmeters, the output frequency is the target, so changes in the piezoelectric element's sensitivity to temperature are not a problem.
In the case of a mass flow meter, the absolute value of the lift force is required, so
Changes in the sensitivity of the piezoelectric element, etc. have a large effect on the measurement value, resulting in large measurement errors.

The present invention solves this problem.

An object of the present invention is to provide a mass flowmeter with good temperature characteristics by installing a resistance temperature detector near the stress detection sensor and using the output thereof to compensate for the piezoelectric constant modulus characteristics of the piezoelectric element. There is something to do.

(Means for Solving the Problems) In order to achieve this object, the present invention provides a mass flowmeter that measures the flow rate of a measured fluid by using a Karman vortex signal that acts as an alternating force. A columnar force receiving body inserted at right angles to M'13 of the force receiving body, a recess provided in the axial direction of the force receiving body, and a piezoelectric element disposed at a position where the stress due to the alternating force in the recess is approximately zero. A first stress detection sensor having a first stress detection sensor, a second stress detection sensor disposed in the recess at a position other than the first stress detection sensor arrangement position, and a second stress detection sensor that is inserted with a gap such that its side surface does not come into contact with the recess, and one end thereof A columnar push rod which presses and fixes the stress detection sensor in the recess and whose other end is fixed at the opening of the recess, an insulating body that insulates the stress detection sensor, and a vortex signal from the stress detection sensor. 7. A signal conversion circuit that converts a signal, a filter circuit that reduces high frequency and low frequency noise of the signal from the signal conversion circuit, and 7. a first amplifier circuit that amplifies the signal from the filter circuit, and the first amplifier circuit. A comparator that converts the signal from the comparator into a pulse signal, and an F/V that converts the signal from the comparator into a DC voltage proportional to its frequency.
a first signal processing circuit comprising a converter, a second amplifier circuit that amplifies the signal from the signal conversion circuit, a detection circuit that detects the signal from the second amplifier circuit, and four signals from the detection circuit. a second signal processing circuit comprising a rectifier circuit that removes ripples from the second signal processing circuit; a division circuit that divides the signal from the second signal processing circuit by the signal from the first signal processing circuit; a gate circuit that sets the output of the divider circuit to 0 when the signal from the amplifier no longer reaches the set trigger level of the comparator; and a gate circuit between the first signal processing circuit and the divider circuit or the second divider circuit; The force receiving body is provided between the signal processing circuit and the dividing circuit and is formed by the temperature characteristics of the piezoelectric constant of the piezoelectric element, the temperature expansion of the force receiving body and the conduit, and the recessed portion. and a compensation circuit for compensating for a temperature error based on a temperature change in bending stiffness between the external portion and the inner cylinder portion formed by the stress detection unit, the insulator, and the fixed body for 1M.
B. The M flowmeter is configured such that the time constant of the rectifier circuit and the time constant of the rectifier circuit of the F/V converter are approximately the same and are greater than the beat frequency of the vortex signal. .

(Operation) In the above configuration, when the measurement fluid flows, a Karman vortex is generated. This Karman vortex causes an alternating force to act on the force-receiving body. In the second stress detection section, alternating stress is generated and detected as an electrical signal. 1st. Second
The vortex signal from the stress detection section is converted into a signal by a signal conversion circuit,
A first signal processing circuit converts it into a DC signal. In other words, the filter circuit reduces high frequency and low frequency noise, and the first
The signal is amplified by the amplifier circuit and converted to a pulse signal by the comparator. Next, an F/V converter converts the pulse signal into a DC voltage proportional to its frequency.

- A second signal processing circuit processes the signal from the signal conversion circuit. That is, amplify with the second LIfJ @ device,
Detected by a detection circuit. Next, a rectifier circuit removes the ripple.

The signal from this rectifier circuit is divided by the signal from the F/V converter in a dividing circuit to obtain an electrical signal corresponding to the flow rate.

On the other hand, if the signal from the first amplifier does not reach the set trigger level of the comparator, the output from the divider circuit is reduced to 0 by the gate circuit by the signal from the F/V converter.
shall be.

Furthermore, temperature compensation is performed by a compensation circuit that compensates for temperature errors based on the piezoelectric constant of the piezoelectric element, the temperature expansion of the force receiving body and the conduit, and the temperature change due to bending between the outer part and the inner cylindrical part.

Examples will be described below.

(Embodiment) Figures 1 (A) and (B) are explanatory diagrams of the configuration of an embodiment of the present invention, in which (A) is a front view, (B) is a side view, and Figure 2 is the detector shown in Figure 1. FIG. 3 is a diagram illustrating the bending moment shown in FIG. 2.

In the figure, 10 is a vortex flowmeter detection 2; and 20 is a vortex flowmeter converter.

In the vortex flow meter detector 10, 11 is a pipe through which the fluid to be measured flows, 12 is a cylindrical nozzle provided perpendicularly to the pipe 11, and 13 is a columnar vortex inserted perpendicularly into the pipe 11 through the nozzle 12. A generator made of stainless steel etc.
m131 is fixed to the nozzle I2 by screws or welding, and the lower end 132 is supported by the pipe line 11 by a plug.The fluid contact part 133 of the six vortex generators 13 that contacts the fluid to be measured produces a Karman vortex street in the fluid to be measured. It has a cross-sectional shape, such as a trapezoid, for example, so as to stabilize and strengthen changes in lift, and has a recess 134 on the upper end 131 side. 135 is an outer cylindrical portion formed in the vortex generator 13 by the recess 134. 14 is a sensor section, in which a first stress detection sensor 142 and a second stress detection sensor 1 are installed in the recess 134 of the vortex generator 13.
41 are pressed and fixed at regular intervals. Then,
As shown in FIG. 3, the first and second stress detection sensors 142 and 141 are arranged on the same side or on both sides of the position A where the stress generated in the vortex generator 13 by the disturbance force N forms a letter. Below, we will explain the gifts placed on the same side. In the sensor section 14, the bottom 143 made of stainless steel or the like acts as a buffer between the first stress detection sensor 142 and the bottom surface of the recess 134, and compensates for the difficulty in controlling the roughness of the bottom surface of the recess 134 during processing. A first spacer 144 made of stainless steel or the like, an insulating plate 145 made of ceramic or the like, and a second spacer +46 made of stainless steel determine the distance between the first stress detection sensor 142 and the second stress detection sensor 141, and also provide insulation between them. It is for carrying out. A push rod 147 made of stainless steel or the like is welded to the upper end +31 of the vortex generator 13 while pressing the sensors 141 and 142, and presses and fixes the sensors 141 and 142. In addition, the sensor part 14 is attached to the vortex generator 13 with an underlay +43 and a push rod 147.
It is designed to make contact only at the top of the The stress detection sensors 141 and 142 are composed of a disk-shaped piezoelectric element 140,
The center of the ◆ is arranged so that it coincides with the neutral axis of the vortex generator 13. Further, the piezoelectric element +40 has electrodes +401, 1402, symmetrically divided into left and right sides with respect to the flow direction of the measurement fluid (arrow direction in the figure) on the front and back sides of the piezoelectric element +40, respectively, as shown in the perspective view of FIG. 1403.1404 is provided,
and in the direction of the arrow (direction of lift of the vortex) as shown in Figure 4 (B)
[F] force (compressive stress and tensile stress) generated in opposite directions across the neutral axis due to the bending moment due to J
A charge generated between electrodes 1401 and 1402 in response to
The polarization is reversed so that the charges generated between the electrodes 1403 and 1404 have the same polarity. Therefore, as shown in Fig. 4(C), for stresses occurring in the same direction, both sides are affected. Charges of opposite polarity are generated between the l poles. In addition, charges generated by stress in the flow direction of the fluid to be measured are canceled between the electrodes and do not appear, and electric charges VJ generated by pipe vibration in the flow direction are also canceled between the electrodes and do not appear.

The second stress detection sensor 141 has electrodes 1401 and 1402.
In order to make the sum of charges of the same polarity generated between the electrodes 1403 and 1404 the output charge 91 and cancel the charges of opposite polarity, the electrodes 1401 and 1403 are commonly connected to the vortex generator 13 through a push rod 147. It is connected to a reference point, and electrodes 1402 and 1404 are commonly connected to a lead wire 1481 via a spacer +46. 1st
The stress detection sensor 142 outputs the sum of the charges of the same polarity generated between the electrodes 1401, 1402 and 1403 and 1404 as the output charge q2, and cancels the charges of '& polarity, and reverses the polarity with q. , the electrode 14
01 and 1403 are commonly connected to a lead wire 1482 via a spacer 144, and electrodes 1402 and 1404 are commonly connected to the vortex generator 13, ie, reference, via an underlay 143.

The lead wires 1481 and 1482 are taken out to the outside through the through holes provided in each part of the sensor section 14 and the hermetic seal 148, and connected to the vortex flow meter converter 20. In order to prevent dew condensation, a gas with a low dew point is filled in the part of the vortex generator 13 surrounded by the recess 134 and the sensor part 14, and the push rod 147 has a communication hole 1 for the filled gas.
49 are provided.

FIG. 5 is a block diagram of the electrical circuit 30 of FIG. 2 (not shown in FIG. 2).

31.32 is a charge converter and stress detection sensor 1
AC charge q1. detected by 4L142. Q2 is AC voltage E
31. Convert to E32. 33 is an addition/subtraction circuit which adds the outputs from charge converter 3+ and 32 to obtain AC voltage E.
33. 51 is iB of the signal from the addition/subtraction circuit 33
The temperature compensation circuit 5I, which is a temperature compensation circuit that performs temperature compensation, includes a temperature sensing resistor 511 provided on the fixed body 147 near the second stress detection sensor 141, as shown in FIG. The temperature of the resistance temperature detector 511 is determined by the fixed body output Ea+,
A desired calculation is performed on E3e, and a signal E12 related to the density or mass flow rate of the fluid is extracted from its output. 43 is a gate circuit, which receives the AC voltage E311 from the first amplifier circuit 38.
When the temperature does not reach the set trigger level of the Schmitt circuit 39, the output of the divider circuit 42 is set to 0. Thus, the time constant of the rectifier circuit 36 and the time constant of the F/V converter 41 are made substantially the same and are configured to be greater than the beat frequency of the vortex signal.

In the above configuration, in order to accurately detect the absolute value of the fluctuating lift signal, there is a signal conversion circuit with a flat f characteristic within the vortex frequency band! '3 (charge converter 31, 32 and addition/subtraction circuit 33) convert the physical quantity into an electrical quantity, and then amplify it in the second amplifier circuit 34, which similarly has a flat f characteristic within the vortex frequency band, and directly convert it to the detection circuit 35. was used as the input.

In order to reduce the high frequency and low frequency noise contained in the vortex signal, the vortex frequency detection is performed using a filter circuit 37 and a The recess 1471 provided in the first amplifier circuit 147 has good heat transfer, and the fixed body 14
It is sealed using a heat-resistant epoxy resin or ceramic filler whose coefficient of thermal expansion is equal to that of the metal chips constituting 7. 34 is a second amplification circuit that amplifies the AC voltage E33 to obtain an AC voltage E34. 35 is a detection circuit that detects the AC voltage E34 and sets it as Esfi. 36 is a rectifier circuit that removes ripples from the AC voltage E35. The second amplifier circuit 34, the detection circuit 35, and the rectifier circuit 36 constitute a second signal processing circuit 302. A filter circuit 37 removes low-frequency or high-frequency noise contained in the AC voltage E13 to obtain an AC voltage E37. 38 is the first amplifier circuit;
AC voltage E) 7 is amplified to obtain AC voltage E, a. 39
is a Schmitt trigger circuit which converts the AC voltage E38 into a constant level pulse signal P39. 41 is an F/V converter which converts the pulse signal PIIl into a DC voltage E41 proportional to its frequency. The filter circuit 37, the first amplifier circuit 38, the Schmitt trigger circuit 39, and the F/V converter 4I constitute a first signal processing circuit 30+.

42 is a divider circuit, F/V converter 41 and rectifier port! 8
After passing through 3638, Schmitt circuit (comparator)
There were 39 inputs.

As a result of the above, by separating the variable lift signal detection circuit and the vortex frequency detection circuit immediately after the signal conversion circuit,
It was possible to both accurately measure the absolute value of the fluctuating lift signal and reliably detect the vortex frequency.

Next, in the embodiment shown in FIG. 1, as shown in FIG. 6, the variable lift force FL is expressed by the following formula.

However, ζ C liver fluctuating lift coefficient ρ; density ■; flow velocity d; diameter of the vortex generator facing the flow n: eef inner diameter Therefore, the signal bending moment Ms of the vortex generator 13 due to the fluctuating lift FL is ρ; Length in the longitudinal direction
Young's modulus of 11; moment of inertia of outer cylinder +35 E1:
The stress in the sensor part 14 is y according to the Young's modulus of
; Area dl of the piezoelectric element 140; ; Piezoelectric constant.

From equations (14) to (18) Qs-M’5ccp V2 (19) If ■ is the achievement flow rate as Q, then The mass flow rate is obtained.

In this case, if there is a temperature change, the constants represented by equations (I4) to (21) change, causing an error.

The largest temperature error is the temperature characteristic of the piezoelectric constant dll of the piezoelectric element. In addition, the change in the degree of change in IIEI/1oEo and d is also relatively large, which poses a problem in accurate mass flow rate measurement.

2. Although FIG. 5 shows a block diagram of the principle of immersion correction, the explanation will be made using specific numerical values and circuit constants.

Now, if we use a crystal, for example, as a piezoelectric element, the temperature coefficient of its piezoelectric constant dll will be 6%/℃ or 11
EI, / 1oEo, and temperature change of d is -0,0
04%/'C, the total is -0.02%/'C
It is necessary to perform temperature correction. If a platinum resistance thermometer is used and +000 is used, the temperature coefficient has non-linearity as shown in Figure 7, but between 0 degrees and 200 degrees it becomes a straight line of 0.38570/"C. Let's think about it.

As shown in FIG. 8, the feedback circuit of the amplifier 512 is
It consists of 0Ω and a resistor R. However, 177°13+R+
= (1+ 0.02x200) (100+R+
) to R, -18280.

In other words, the gain of the temperature compensation circuit 51 is +0 per 1°C.
．． The temperature error can be corrected by increasing the temperature by 0.02%.

However, the temperature characteristics of platinum resistance thermometers are nonlinear;
There will be an error at temperatures other than 200°C, but the hair will eventually reach 0°C to 3°C.
In the temperature range of 00℃, the mass flow rate error is 0.1%.
It is as follows and can be ignored.

As a result, by supplementing the humidity characteristics such as the piezoelectric constant of the piezoelectric element, a mass flowmeter with good temperature characteristics can be obtained.

FIG. 9 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, a temperature compensation circuit 61 is provided between the first signal processing circuit 301 and the division circuit 42.

That is, the denominator side of the arithmetic circuit 42 is temperature compensated. (ρv2)/v, ρv2 is −
Since it has a temperature coefficient of 0.02%/'C,
Temperature compensation becomes possible by similarly supplementing (2) by -0.02%/'C.

A specific example of the configuration of the temperature compensation circuit 61 is shown in FIG.

The input stage of the amplifier 611 is composed of platinum of 100Ω and a resistor R2. However, from R,=17510.

It goes without saying that the temperature compensation circuit 61 may be a simple voltage dividing circuit without the amplifier 611.

In addition, in the above-mentioned embodiment, the temperature compensation r4 circuit 51 is
Although it is arranged before the second amplifier circuit 34, it goes without saying that it may be arranged before the detection circuit 35 or the rectifier circuit 36.

In addition, in the described embodiment, a so-called stress detection method was described in which the alternating stress of a vortex generator with -+4 fixed and one end supported was detected, but a vortex generator with one end fixed and one end free was described. It may also be a device that detects alternating stress.

Also, other force detection methods for detecting fluctuating lift forces, e.g.
The sensor's mechanical constant (Young's modulus) due to changes in humidity also applies to displacement, strain, torque, etc.

By temperature-compensating changes in the spring constant, a mass flowmeter using Karman vortices can be constructed.

(Effects of the Invention) As explained above, the present invention provides a mass flowmeter that measures the flow rate of a fluid to be measured using Karman vortex signals that act as cross-over forces. A first stress detection device that includes an inserted columnar force receiving body, a recess provided in the axial direction of the force receiving body, and a piezoelectric element disposed at a position where the stress due to the alternating force in the recess is approximately zero. a second stress detection sensor disposed in the recess other than the first horn detection sensor arrangement position; the second stress detection sensor is inserted into the recess with a gap such that the side surfaces thereof do not come into contact with each other; a columnar push rod that is pressed and fixed and whose other end is fixed at the opening of the concave portion 11iI; an insulator that insulates the stress detection sensor; a signal conversion circuit that converts the vortex signal from the stress detection sensor; a filter circuit that reduces high frequency and low frequency noise in a signal from the signal conversion circuit; a first amplifier circuit that amplifies the signal from the filter circuit; and a comparator that converts the signal from the first amplifier circuit into a pulse signal. l A first signal processing circuit comprising an F/V converter that converts No. 13 from the comparator into a DC voltage proportional to its frequency, and a second amplification circuit that amplifies the signal from the signal conversion circuit No. 1J, a second signal processing circuit comprising a detection circuit for detecting a signal from the second amplifier circuit and a rectification circuit for removing ripples from the signal from the detection circuit; and a signal from the second signal processing circuit. l
li A division circuit that divides by the signal from the first signal processing circuit, and an output of the division circuit set to O when the signal from the first amplifier no longer reaches the set trigger level of the comparator. temperature characteristics of the piezoelectric constant of the piezoelectric element provided between the first FA processing circuit and the division circuit or between the second signal processing circuit and the division circuit; and of the force receiving body and the conduit? The bending stiffness of the outer cylinder portion of the force-receiving body formed by the concave portion and the inner cylinder portion constituted by the stress detection portion, the insulator, and the fixing body is based on the temperature change. a compensation circuit for compensating for the amplitude error, and the time constant of the rectifier circuit and the time constant of the rectifier circuit of the F/V converter described in 1IiI are made substantially the same and larger than the beat frequency of the vortex signal. Since the mass flowmeter is constructed with a mass flowmeter of I can do two things.

Therefore, according to the present invention, a mass flowmeter with good temperature characteristics can be realized by installing a resistance temperature detector near the stress detection sensor and compensating for the temperature characteristics such as the piezoelectric constant of the piezoelectric element using the output thereof. be able to.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram of an embodiment of the present invention, (A) is a front view, (B) is a side view, and FIG. 2 is a configuration explanatory diagram showing a cross section of the detector section of FIG. 1, fJS3 The figure is an explanatory diagram of the operation of Figure 2, Figure 4 is an explanatory diagram of the main part of Figure 2, Figure 5 is the electric circuit diagram of Figure 1, and Figures 6, 7, and 8 are the diagrams of Figure 2. FIG. 9 is an explanatory diagram of the main part configuration of another embodiment of the present invention.
Fig. 0 is an explanatory diagram of the main part configuration of Fig. 9, Fig. 11 is an explanatory diagram of lift, etc. when a vortex generating body is placed in the pipe, Fig. 12 is an explanatory diagram of the drag coefficient, and Fig. 13 is an explanatory diagram of the conventional FIG. 14 is an explanatory diagram of the configuration of a conventional example that is more commonly used, and FIG. 14 is an explanatory diagram of the parts of FIG. 13. 10... Vortex flow rate detector, 11... Pipe line, 12...
Nozzle, 13... Vortex generator, 131... Upper end, 13
2...lower end, 133...platform body part, 134...
Recessed portion, 135...Outer cylinder portion, 14...Sensor portion, +4
0... Piezoelectric element, 141... Second stress detection sensor, 142... First stress detection sensor, +43... Underlay, 144... First spacer, 145... Insulating plate , 146... second spacer, 147... push rod,
147I... recess, 1372... filler, +48.
...Hermetic seal, 148+. I482...Lead wire, 149...Communication hole, +40
1.1402.1403゜1404... Electrode, 15.
... Labyrinth flow path, +51 ... Fin, 152.
... Enlargement chamber, 20... Vortex flow meter converter, 30... Electric circuit, 301... First signal processing circuit, 302...
2nd signal processing circuit, 31. 32... Charge converter, 33... Addition/subtraction circuit, 34... Second amplifier circuit,
35... Detection circuit, 36... Rectifier circuit, 37...
Filter circuit, 38... First amplifier circuit, 39... Schmitt trigger circuit, 41... F/V converter, 4
2... Division circuit, 43... Gate circuit, 51.61
... Temperature compensation circuit, 511 ... Temperature measuring antibody, 512
．． 612...Amplifier. Figure 1 (A) @ Figure 3 Figure 4 (A) (I3) Figure 1 Figure i Figure 7 Ward Figure 11 Figure 1Z Figure t3 Figure 14

Claims (1)

[Claims] In a mass flow meter that measures the mass flow rate of a fluid to be measured using a Karman vortex signal that acts as an alternating force, there is a columnar force-receiving body inserted perpendicularly into the pipeline of the fluid to be measured, and an axial direction of the force-receiving body. a first stress detection sensor having a piezoelectric element disposed at a position where stress due to the alternating force in the recess is substantially zero; and a first stress detection sensor disposed in the recess at a position other than the first stress detection sensor arrangement position. a second stress detection sensor, which is inserted into the recess with a gap such that its side surfaces do not come into contact with each other, and has one end that presses and fixes the stress detection sensor in the recess, and the other end that is fixed at the opening of the recess. a rod, an insulator that insulates the stress detection sensor, a signal conversion circuit that converts the vortex signal from the stress detection sensor, and a filter circuit that reduces high frequency and low frequency noise of the signal from the signal conversion circuit. A first amplifier circuit that amplifies the signal from the filter circuit, a comparator that converts the signal from the first amplifier circuit into a pulse signal, and an F/V converter that converts the signal from the comparator into a DC voltage proportional to its frequency. a first signal processing circuit comprising: a second amplifier circuit that amplifies the signal from the signal conversion circuit; a detection circuit that detects the signal from the second amplifier circuit; and a ripple component of the signal from the detection circuit. a second signal processing circuit comprising a rectifying circuit for removing the signal; and a signal from the second signal processing circuit to the first signal processing circuit.
a division circuit that divides by a signal from a signal processing circuit; and a gate circuit that sets the output of the division circuit to 0 when the signal from the first amplifier no longer reaches a set trigger level of the comparator; Temperature characteristics of the piezoelectric constant of the piezoelectric element provided between the first signal processing circuit and the division circuit or between the second signal processing circuit and the division circuit and the force receiving body and a temperature change in bending stiffness between the outer cylindrical portion of the force receiving body formed by the temperature expansion of the conduit and the recess, and the inner cylindrical portion composed of the stress detection portion, the insulator, and the fixed body. and a compensation circuit for compensating for a temperature error based on the vortex signal, the time constant of the rectifier circuit being substantially the same as the time constant of the rectifier circuit of the F/V converter and being greater than the beat frequency of the vortex signal. A mass flow meter.