Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
  • G01F1/78—Direct mass flowmeters
  • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
  • G01F1/84—Coriolis or gyroscopic mass flowmeters
  • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
  • G01F1/8427—Coriolis or gyroscopic mass flowmeters constructional details detectors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
  • G01F1/78—Direct mass flowmeters
  • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
  • G01F1/84—Coriolis or gyroscopic mass flowmeters
  • G01F1/845—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits
  • G01F1/8468—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits
  • G01F1/849—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits having straight measuring conduits
  • G01F1/8495—Coriolis or gyroscopic mass flowmeters arrangements of measuring means, e.g., of measuring conduits vibrating measuring conduits having straight measuring conduits with multiple measuring conduits

Definitions

• the invention relates to a mass flow meter working according to the Coriolis principle with a mechanical vibration system and with an optical sensor device which detects the mechanical vibrations of the vibration system and which has a light transmitter and a light receiver, the light of the light transmitter being used as a light receiver by a Light guide device is transmitted, which has at least one quartz or sapphire rod and the luminous flux of which can be influenced by the vibrations.
• the light guide device consists of two sapphire rods, of which one sapphire rod is connected at one end to the light transmitter and the other sapphire rod is connected at one end to the light receiver.
• the other ends of the two sapphire rods are designed as totally reflecting prisms and are spaced apart in this way. that the light flux passing through the sapphire rod from the light transmitter passes into the other sapphire rod and is conducted by the latter to the light receiver.
• Dip plugs are attached to the measuring tubes of the mass flow meter in such a way that, depending on the deflections of the measuring tubes, they protrude more or less far into the gap formed between the prism-shaped ends of the sapphire rods.
• the advantage is achieved that the light transmitter and light receiver can be accommodated at a distance from the oscillating measuring tube system, so that they are not exposed to strong temperature fluctuations when cold and hot fluid alternately flows through the measuring tubes. Furthermore, it is avoided that the measuring tube system set in mechanical vibrations transmits undesirable vibrations to the light transmitter and the light receiver or that these are attacked by a chemically aggressive fluid that may emerge from the measuring tubes. In contrast, the sensitive sapphire rods of the light guide device are exposed to such thermal, chemical and mechanical effects.
• a light guide is known from US Pat. No. 4,173,393, which has a core made of quartz, a cladding made of glass and a protective coating made of metallic glass.
• the protective coating of metallic glass is applied in liquid form and contracts more strongly than the glass of the cladding during solidification, as a result of which the light guide is placed under constant compression, which increases the breaking strength.
• the invention has for its object to provide a mass flow meter operating according to the Coriolis principle, the light guide device of which is characterized by mechanical stability and resistance to corrosion and temperature.
• this object is achieved in that the or each quartz or sapphire rod of the light guide device is surrounded by ceramic material or glass.
• the ceramic material or glass surrounding the rods of the light guide device improves the mechanical strength of the light guide device and protects the quartz or sapphire rods of the light guide device from chemical and thermal influences.
• the optical properties of the light guide device are not impaired by the embedding in ceramic material or glass, since ceramic or glass has a lower refractive index than quartz or sapphire. It is particularly advantageous to use types of glass which are suitable for industrial use and which are suitable for binding to sapphire and are chemically and thermally robust. Their refractive index is around 1.5, which is lower than that of sapphire.
• An advantageous development of the invention is that the outside of the ceramic material or glass is surrounded by a metal sheath. This further increases the chemical resistance and mechanical strength of the light guide device.
• the metal cladding also has the advantage that the light guide device can now easily be attached to metallic objects, e.g. a metallic support housing can be attached.
• FIG. 1 is a schematic representation of a light guide device designed according to the invention
• FIG. 2 shows the installation of the light guide device according to FIG. 1 in a mass flow meter working according to the Coriolis principle
• FIGS. 1 and 2 show another embodiment of the light guide device and its installation in a mass flow meter operating according to the Coriolis principle. Identical parts are provided with the same reference numerals in FIGS. 1 and 2.
• the transmitted luminous flux is, as will be explained with reference to FIG. 2, influenced by mechanical vibrations of the flow device of a Coriolis force mass flow meter.
• a luminescence diode can be used as the light transmitter 1.
• the light receiver 2 is a photoelectric converter, which converts the received light into an electrical signal, which represents a sensor signal.
• a PIN diode in the infrared range (for example at a wavelength of 880 nm) can be used for this.
• the light guide device 3 is formed from two sapphire rods 4 and 5 arranged at a short distance from one another and parallel to one another. These are connected at one end to the light transmitter 1 or to the light receiver 2, while their free other ends are chamfered at an angle of 45 °, so that the oblique end faces 6 and 7 formed thereby are at a right angle to one another stand.
• the beam path of the light flux emitted by the light transmitter 1 produced by this configuration is shown in FIG. 1 by the dashed line 8.
• the light propagates essentially axially until it hits the oblique end face 6, where it is totally reflected at an angle of 90 °. It passes through the air gap 9 existing between the two sapphire rods 4 and 5 and meets the oblique face 7 of the sapphire rod 5, where it is totally reflected again at an angle of 90 °. It spreads essentially axially in the sapphire rod 5 and strikes the light receiver 2.
• the two inclined end faces 6 and 7 thus deflect the light by 180 ° in the manner of a right-angled prism.
• the sapphire rods 4, 5 are embedded in a ceramic or glass body 13, which is shown in cross-section (hatched) in the drawings. As can be seen in particular from FIG. 2, the cross-sectional area of the ceramic or glass body 13 is substantially larger than the cross-sectional areas of the sapphire rods 4 and 5 embedded therein.
• the ceramic or glass body 13 serves to increase the strength of the Light guide device. To further increase the strength, the ceramic or glass body 13 is surrounded by a metal sheath 14. Since the ceramic or glass body 13 has a lower refractive index than the sapphire rods 4, 5, the losses of light energy during light transmission in the sapphire rods 4, 5 are minimized.
• the metal sheath 14 can be applied as a metal layer on the outer surface of the ceramic or glass body 13; however, it is preferably a prefabricated metal sleeve which is filled with the ceramic material or glass 13 in which the sapphire rods 4 and 5 are embedded.
• FIG. 2 the arrangement of FIG. 1 for forming a displacement sensor is installed in a Coriolis force mass flow meter with two parallel measuring tubes M in such a way that the siphon rods 4, 5 extend perpendicular to the longitudinal axes of the measuring tubes M. Their inclined end faces 6, 7 lie between the measuring tubes M. On each measuring tube M a plunger 10 or 11 is fastened perpendicular to the longitudinal axis of the measuring tube so that it projects into the air gap 9 between the sapphire rods 4, 5.
• the two plungers 10, 11 lie in one plane, and their mutually facing edges are at a distance from one another, so that there is a gap 12 between these edges, through which part of the light flux reflected on the end face 6 from the sapphire rod 4 to Go sapphire wand 5 can. If, according to the mass flow measurement according to the Coriolis principle, the two measuring tubes M are set into mutually opposite vibrations, the gap 12 between the plungers 10, 11 alternately becomes wider and narrower in time with the vibrations. The intensity of the luminous flux coming from the sapphire rod 4 to the sapphire rod 5 is thereby modulated. Thus, the amplitude and the phase of the modulated luminous flux and consequently also the amplitude and the phase of the sensor signal emitted by the light receiver 2 correspond to the amplitude and the phase of the vibrations of the measuring tubes M.
• Fig. 3 shows a modified embodiment of the light guide device, which is suitable for this case.
• the light guide device 23 of FIG. 3 again contains two sapphire rods 24 and 25, which are connected at one end to a light transmitter 21 or a light receiver 22.
• the other ends of the sapphire rods 24 and 25 are not beveled, but rather are provided with flat end faces 26 and 27 which are perpendicular to the longitudinal axis and which are translucent.
• the light guide device 23 is mounted so that the end faces 26 and 27 are opposite a measuring tube M at a short distance.
• the measuring tube M has a reflective outer surface at least in the region which lies opposite the end faces 26 and 27.
• the sapphire rods 24 and 25 are embedded in a ceramic or glass body 28, which in turn is surrounded by a metal sheath 29, which results in the advantageous effects described above.
• the light emitted by the light transmitter 21, which propagates through the sapphire rod 24, emerges from the end face 26, so that it strikes the reflecting outer surface of the measuring tube M.
• Part of the light reflected by the measuring tube M strikes the end face 27 of the sapphire rod 25, in which it propagates to the light receiver 22.
• the strength of the reflected light entering the sapphire rod 25 depends on the distance between the end faces 26, 27 and the measuring tube M. If the measuring tube M is vibrated, as indicated by the double arrow in FIG.
• this distance changes in time with the vibrations, so that the intensity of the light emitted by the sapphire rod 24 after reflection on the measuring tube M into the sapphire rod 25 is transmitted, is modulated according to the vibrations.
• the light receiver 22 supplies a vibration sensor signal modulated in time with the vibrations.
• the sapphire rods 24 and 25 are therefore closer together in FIG. 3 than the sapphire rods 4 and 5 in FIG. 1.
• quartz rods can also be used instead of the sapphire rods.
• the ceramic or glass body and the surrounding metallic sheath as shown in FIG. 2, to have a rectangular cross-sectional profile.
• the cross-sectional profile of these parts is arbitrary and in particular can also be circular.

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• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Volume Flow (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6354122

Family Applications (1)

Country Status (5)

Families Citing this family (13)

Family Cites Families (9)

• 1989
  • 1989-05-10 EP EP89905684A patent/EP0377005A1/de not_active Withdrawn
  • 1989-05-10 JP JP1505456A patent/JPH02503359A/ja active Pending
  • 1989-05-10 WO PCT/EP1989/000517 patent/WO1989011084A1/de not_active Ceased
  • 1989-05-10 US US07/457,814 patent/US5020380A/en not_active Expired - Fee Related
• 1990
  • 1990-01-05 DK DK003090A patent/DK3090A/da not_active Application Discontinuation

Non-Patent Citations (1)

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