TWI220157B - Coriolis force type flow meter using an optical interferometer - Google Patents

Abstract

There is provided a Coriolis force type flow meter, which is a device using an optical interferometer for measurement. When a conductive pipe through which fluid flows produces a bending vibration due to external exciting source, the conductive pipe also produces a twist vibration due to the effect of Coriolis force. Furthermore, an optical interferometer is used to measure tiny amplitude angle change when the conductive pipe is vibrating, thereby determining the flow magnitude of the fluid flowing through the conductive pipe.

Description

1220157 _ Case No. 91125289_ Year Month Date __ V. Description of the Invention (1) [Field of the Invention] The present invention relates to a Coriolis force flowmeter, in particular to a Coriolis using an optical interferometer as a measuring device Force type flowmeter. [Background of the Invention] In many processes or application technologies that require flow control, the first thing that must be done is to be able to accurately measure and control the size of the flow in order to make the desired product, such as : In biochemical technology, the compounding of a certain compound requires the mixing of two or more substances according to a special ratio in order to produce this compound; or in automobile and motorcycle engines, the oil-gas ratio must be precisely controlled. To achieve better efficiency of the engine. At present, the principle of most flowmeters is to use the measurement of the fluid flow through the conduit, the fluid pressure, temperature changes, or changes in its transmission sound wave properties to estimate its flow rate, and according to its measurement method Different types of flowmeters can be divided into heat transfer type, differential pressure type, and ultrasonic type. The physical quantities measured by the above flowmeters are usually flow velocity (meters / second) or volume flow rate (cubic Meters / second), and then the density of the fluid can be used to determine the mass flow rate of the fluid to be measured. However, in the above flowmeter, the method of measuring fluid flow is an indirect measurement method, and the accuracy of measuring the flow rate is very easy to change due to changes in the properties of the fluid, such as: temperature, pressure, density, Viscosity, homogeneity, and other properties change, and even will be affected by the distribution characteristics of the flow field, so it is impossible to accurately measure the correct flow of the fluid. To overcome the shortcomings of the above flowmeter, Micr0M 〇 ti ο η company first

1220157

1 997 ^ = To develop a ^ 1 meter made using the principle of Coriolis force (c〇〇〇1 is F〇rce) by directly or indirectly measuring the fluid flowing in a rotating tube Force can measure the mass flow of the fluid. This kind of flowmeter can directly measure the flow rate of the fluid in the government, and the biggest advantage is that its measurement accuracy does not change to the effect of the change in fluid characteristics, and it can achieve high precision. However, this This Coriolis force type flowmeter also has its shortcomings, that is, in order to measure small changes in the flow field caused by Coriolis force, this flow rate a must be relatively large and not complicated. The measurement f can reach the requirement of high accuracy. In this way, it will increase the production cost of the entire flow meter, and it is less applicable to the measurement of low-flow fluid. The method disclosed in U.S. Patent No. 6,4 1 2,355 (US Patent No. 6, 4 1 2 '3 5 5), the design concept is the same as that of the μ MoMo ti on company, but the amount The measurement method is to measure the electronic signal of two points at different positions in a catheter to calculate the relationship between the phase difference and the excitation frequency to obtain the magnitude of the flow in the catheter. However, this type of flow meter has a large overall size and a complicated device, so it is not suitable for fluid measurement in low flows. In 1996, a paper published by the International Institute of Electrical and Electronics Engineers (〗 EEE) En ^ won et al. “A Coriolis Mass Flow Sensor Structure in Si 1 ic on a silicon wafer” ο n ·), they used the laser light projected on the dual circuit guide to change the movement state, and then measured the position change of the reflected light on the light detector to estimate the size of the rotation angle, and then obtained the Flow value. Moreover, the positioning and calibration of the entire optical measurement system is very difficult, and will affect; ^ 1 sensitivity is affected 'so' must be obtained through other ways

1220157 M% 9112528Q V. Description of the invention (3) Month, month, and day, Correction, such as: increasing the input voltage of the shaker. [Objective and summary of the invention] # 1 In view of the difficulties encountered by the above flowmeters during measurement, the purpose of this month is to provide a method for using an optical interferometer (Fabry-Perot

InteTferometer) is a Coriolis force flowmeter that measures the flow in the catheter. Because the sensitivity of the foot 2 optical interferometer can reach the level of micrometers, it is' very suitable for measuring small flow changes in the catheter, and the entire optical interferometer The device and calibration are not complicated, which can reduce the manufacturing cost of the entire measurement device, thus improving the competitive advantage of Coriolis force flow meters compared to other types of flow meters. The Coriolis force flowmeter using optical interferometers developed by Gabbenfa 2 has a structure including: on a substrate, an excitation current 2 ′ for providing electrostatic force, and symmetrical sides of the excitation electrodes. Each has perforations. A symmetrical ^ rectangular loop duct is provided on this substrate ^, the rear end of which is for the fluid to enter and exit, and the other end is arranged above the excitation electrode of this substrate. The electrostatic force provided by the excitation pole is driven to drive This rectangular loop conduit flexes and vibrates. Hole, and] the front end of the circuit guide has a through hole corresponding to the above-mentioned perforation, and the tooth holes of the tunu and the through hole of the circuit pipe are traced to the side of the circuit pipe from L, 〒 Lu Xinbei Zha, then set the photodetector above the hole of Jiu Ga ΛΑ g; set the photodetector on the base surface, and the light of ί :::! ^ Can be calculated through the reflection mirror located in the through hole and the perforation. t manipulate the optical signal after interference. Finally, the flow rate to ~ through this rectangular loop duct. Two ~ Ming's purpose, structural features and functions have further

Page 8 1220157 Amendment

____ Case No. 91125289_ January 1B V. Description of the invention (4) Understand that the detailed description with the illustration is as follows: [Detailed description of the embodiment] To measure the small changes caused by Coriolis force in the flow meter, this I 3 designed a rectangular symmetrical circuit conduit. 〇, please refer to the "1 X-,, M", first, let the fluid flow through this circuit conduit 10, and through the exciter ^, circuit conduit 10— This force causes the loop duct 10 to vibrate ('Bending Vibration'). However, due to the Coriolis force, the loop duct 10 will generate twist vibration at the same time. The cross-sectional view of the front end of the loop catheter 10 in the stationary state and the excited state is as shown in FIG. 2, and the dashed rectangle shown in the figure is the front end cross-section of the loop catheter 10 in the stationary state. The solid rectangle shown in the figure is the front cross-section of the loop duct 10 in the state of oscillating. The maximum amplitude angle Θ b of the deflection vibration of the loop duct 10 and the maximum amplitude of the torsional vibration (by the following formula (1) and formula (2) can be calculated by measuring the magnitude of the shifted value. 1) (2) Then bring the maximum amplitude angle Θ b of the flexural vibration and the maximum amplitude angle 0t of the torsional vibration into the "Measurement Systems Application and Design" Ernest 〇. Deobelin ^ McGraw-Hill publishing Company ^ New York, 1990 · (p. 602-p. 605) revealed the formula (7 · 8 0), we can know the formula (3)-flow rate φ and 0 b, 01: Relationship: 1220157 Case No. 91125289 V. Description of Invention

a: the length of the loop duct 10 b: the width of the loop duct 10 f〇: the excitation frequency ks •• torsion elastic coefficient (TorSlonal SpFin to obtain the flow I of the fluid flowing through the loop duct 丨 〇 丄 according to the present disclosure The application of the first embodiment is as follows. The schematic diagram of the first embodiment is as follows: On the base plate 20, an inlet 11 at the rear end of the duct 10 with a rectangular symmetrical circuit is set to flow in, and then to the outlet 12, the flow path is a symmetrical moment. The cross section of the duct 10 with this circuit can be used according to the size of the flowmeter and the process considerations. The cross section of the duct can be designed to be right (丄 f hexagonal, etc., and then the micro-electromechanical technology is used to make the loop. The catheter 丨 0 Μ uses the joining technology to make the upper and lower circuit loops 10. Next, the torsion below the front end of the loop duct 10: Γϋ 'The purpose is to provide an excitation source of two vibrations of electrostatic force. If set The position of the double number two must be the center 1 of the loop duct 10. The position of the perforation 21 on the substrate 20 on the two sides of the excitation electrode 30 is also the same as that of the back soil and the king is symmetrically distributed. Within 21

Stiffness size φ 〇 Involved Coriolis test "Figure 3 ^ The shape of the circuit catheter 10, the circuit catheter 10, the whole. Take a miniature scale shape, for example, the upper and lower bodies of the process are joined together. It can be seen that the shape of the fluid from the rear end can be based on the duct as follows: a rectangular symmetry plane can be processed on the substrate 2 Q, and “the symmetry points are taken as the reference line of the oscillating electrode 30”, each of which has a perforation. The center line of the road duct 10 is a reflection mirror surface provided with the shock path duct 10, the pendulum 1220157

At the distances of the respective circuit guide surfaces, for example, the optical fiber 45 is two surfaces 41, and the mirror surface 47 is below the front end of the circuit conduit 10-Bangu gum corresponds to the position of the perforation 21 above, and there are: reflective mirror surface 47, Please refer to "Fig. 4" The following table of the mirror surface 4! On the base 20 is bonded to the early-mode fiber 4 5 and only gw gF ^ φ ^ ^ ^ X a between the mirror surface 41 and the mirror surface ^ ^ m 1 pie length. Reflective mirrors 41 and 47 are produced using the "basket q 闰 丄-丄 first learning key film technology" in the micro-electro-mechanical process. ^ The light emitted by You Yuan 42 enters through the single-mode :: wheel. In the combiner 44, the light is divided into the following first by the 44, and then the single-mode optical fiber 45 transmits the light to the mirror surface 41, and the light is reflected back and forth between the mirror surface 41 and the reflection. When the length of the resonant cavity is changed, 'light of a specific wavelength will penetrate the mirror 41 and enter the single-mode fiber 45, and pass the light back to the coupler 44 via the single-mode fiber.' At this point, # 合 器 44 will After the received optical signals are coupled, they are transmitted to the photodetector 4 3 for interference. Finally, after the calculation by the signal processor 46, the displacement centroid and L as shown in the "Figure 2" can be obtained, and then calculated by the formula (3). The amount of fluid flowing through the loop conduit Q. The accuracy of the Coriolis force flowmeter used in the entire optical interferometer depends on the characteristics of the optical interferometer used, that is, the wavelength of the light source 42, the reflectance of the reflecting mirror surface 41 and the reflecting mirror surface 47, and the length of the resonant cavity. . Please refer to "Figure 5", which is a schematic diagram of the architecture of the second embodiment of the present invention. 'The architecture of the second embodiment is substantially the same as that of the first embodiment. 21 places have two 1220157

The through hole 1 3 'and the upper part of the through hole 13 are provided below the two perforations 21 of the plate 20, and also the length of the resonant cavity of the reflection interferometer in the perforation 21 and the through hole 13. A corresponding light source 42 is provided, and a corresponding light detector 43 is provided on the base: The distance between the mirror surfaces 41 and 47 is optical * The light emitted by the light source 42 is transmitted to the through-hole 13 and the through-hole 13 through the single-mode fiber 45 The reflective mirror surface 41 in the perforation 21 is then used by the photodetector to "capture the optical signal after interference; then, the single-mode optical fiber 45 is used to transmit the optical signal to the flood signal processor 46 for signal processing, ie The displacement value and can be obtained as shown in "Figure 2", and then the flow rate of the fluid flowing through the loop duct 10 can be calculated by formula (3). The accuracy of the Coriolis force type flow meter using the entire optical interferometer depends on the characteristics of the optical interferometer used, that is, the wavelength of the light source 42, the reflectance of the reflecting mirror 41, and the length of the resonant cavity. [Achieved effect] Lee 5 The Coriolis force flowmeter using the optical interferometer disclosed in the present invention has an accuracy higher than that of the Coriolis force (Coriolis F 〇]: ce) type flowmeter. And its optical interferometer positioning and weighting are better than the Coriolis force flow sensor on a π silicon wafer published by Enoksson et al. (A Coriolis Mws Flow Sensor Sti ^ uctuFe in Si 1 iCon ·) The laser light measurement system used in the flow sensor is easy, so its measurement accuracy is also greatly improved. As the improvement of measurement accuracy 'jointly' can also simplify the design of the Coriolis force flow meter using an optical interferometer 'and reduce the voltage value required for the exciter, it can greatly reduce the overall flowmeter. cost of production. a Ji 户 Jin Speaker ’is just one of the preferred embodiments of the present invention, and amended 1220157 case number 91125289

Page 13 1220157 _ Case No. 91125289 _ year month day __ Brief description of the diagram. The first diagram is a rectangular symmetrical circuit catheter 10 designed by the present invention; the second diagram is the front end of the circuit catheter 10 when it is stationary and excited. Sectional view in the vibration state; FIG. 3 is a schematic structural diagram of the first embodiment of a Coriolis force flowmeter using an optical interferometer disclosed in the present invention; FIG. 4 is a sectional view of a front end of a loop conduit; and FIG. 5 It is a schematic diagram of a second embodiment of a Coriolis force flowmeter using an optical interferometer disclosed in the present invention. [Illustration of Symbols] 10 loop conduit 11 inlet 12 outlet 13 through hole 20 substrate 21 perforation 30 excitation electrode 41 reflecting mirror 42 light source 43 light detector 44 coupler 45 single-mode fiber 46 signal processor 47 reflecting mirror

Page 14

Claims (1)

1220157 Sixth, the scope of patent application 1 · A Coriolis force type flowmeter using an optical interferometer, which includes: a substrate with an excitation electrode that can provide an electrostatic force, and a perforation on each side of the excitation electrode; A symmetrical circuit conduit is mounted on the substrate, the rear end is an inlet and outlet for fluid in and out, and the front end is arranged on the excitation electrode of the substrate. The circuit conduit is driven to flex by the electrostatic force provided by the excitation electrode. Vibration 'the front end of the circuit catheter has a plurality of through holes corresponding to the perforation' and the through holes are located at symmetrical positions; a plurality of reflecting mirror surfaces are respectively disposed in the perforation of the substrate and the through holes of the circuit conduit A plurality of light sources disposed above the through-hole of the circuit conduit; and a plurality of light detectors disposed below the perforation of the substrate; wherein the light detector can capture the light source sequentially through the perforation and the through-hole The optical signal after the interference of the reflecting mirror surface in the hole can be calculated to obtain the flow rate flowing through the symmetrical loop duct. 2 · The Coriolis force flowmeter using an optical interferometer as described in item 1 of the scope of the patent application, further includes a plurality of excitation electrodes, and the excitation electrodes are symmetrically distributed around the center line of the σHai circuit conduit . 3 i The Coriolis force type flowmeter using an optical interferometer as described in item 1 of the scope of the patent application, wherein the loop conduit is manufactured using a chemical etching method of the body type plus I dry etching technology in a micro-electro-mechanical process. j. The Coriolis force & ash meter using an optical interferometer as described in item 1 of the scope of the patent application, wherein the loop duct is a rectangular loop duct. • Coriolis force applied to the optical interferometer as described in item 1 of the patent application Page 15 1220157 _Case No. 91125289 _ Year Modified_ VI. Patent application range type flowmeter, in which the reflecting mirror surface in the through hole of the loop duct has a specific reflectivity. 6. The Coriolis force flowmeter using an optical interferometer as described in item 1 of the scope of the patent application, wherein the distance between the reflecting mirror surface provided in the perforation and the through hole is the resonant cavity length of the optical interferometer . 7. The Coriolis force flowmeter using an optical interferometer as described in item 1 of the scope of the patent application, wherein the reflecting mirror surface is made using optical coating technology in a micro-electro-mechanical process. Page 16