Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01G—WEIGHING
  • G01G9/00—Methods of, or apparatus for, the determination of weight, not provided for in groups G01G1/00 - G01G7/00
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V7/00—Measuring gravitational fields or waves; Gravimetric prospecting or detecting
  • G01V7/08—Measuring gravitational fields or waves; Gravimetric prospecting or detecting using balances

Definitions

• the invention relates to a method and device for measuring a property depending on a mass based on a configuration change of a liquid.
• the problem to be solved is to provide a method and device of this type that is more robust and easier to set up.
• a liquid is placed in a container and has a configuration that depends on the masses around it.
• configuration in this respect, is used to designate the distribution of the liquid within the container. This configuration will primarily depend on the gravitational field of the earth, but (to some minor extent) also on the gravitational field of the masses around it.
• at least one parameter depending on this configuration is measured, and the measured parameter is used to derive the property.
• the term "property” is used for the property of the mass of the body that is to be measured.
• the property can e.g. be:
• the location of the body such as its dis- tance from the container or its direction from the chamber.
• the term "parameter”, on the other hand, is used for the parameter depending on the configuration of the liquid that is determined by the device's detector.
• the parameter can e.g. be a light intensity affected by the configuration, a magnetic or dielectric or electric property that depends on the configuration, or any combination thereof.
• the container when the measured parameter changes, the container is tilted for bringing back the measured parameter to its original value. This allows to bring the container back a defined operating position where the parameter has a given value and the resulting gravitational force at the location of the container has a given direction.
• Fig. 1 is a schematic illustration of a first embodiment of the device
• Fig. 2 is a first embodiment of the container and detector
• Fig. 3 is a diagram of a circuit for processing the signals of the detector of Fig. 2
• Fig. 4 is a second embodiment of the container and detector
• Fig. 5 is a third embodiment of the container and the detector
• Fig. 6 is a fourth embodiment of the con- tainer and the detector
• Fig. 7 is a view of a second embodiment of the device.
• Fig. 8 is an fifth embodiment of the container.
• a first embodiment of the device is schematically shown in Figs. 1 - 3. It comprises a static support 1, which e.g. rests on the floor of a laboratory. Static support 1 carries a movable carrier 2. Movable carrier 2 rests at two locations 3 and 4 on support 1.
• the tilt axis is horizontal, i.e. perpendicular to the gravitational field of the earth.
• movable carrier 2 At location 4, which is at a distance from location 3, movable carrier 2 comprises an actuator 5, such as a piezo-electric actuator, which rests against support 1. Movable carrier 2 can be tilted by operating actuator 5.
• actuator 5 such as a piezo-electric actuator
• movable carrier 2 carries a detector assembly 6.
• Fig. 2 shows a sectional view of an embodiment of this assembly.
• Detector assembly 6 comprises a container 10, which is held in fixed position in respect to movable carrier 2. It has, advantageously, a curved, convex top wall 11 and a bottom wall 12 (curved or flat) opposite to top wall 11. At least top wall 11 and bottom wall 12 are made of a transparent material, such as glass.
• a liquid 13 is located in container 1. It fills all of container 10 except for a region 14, which is either field by a fluid different from liquid 13 or which is empty, i.e. under vacuum.
• the term ⁇ a fluid different from liquid 13" also encompasses a gaseous phase of liquid 13.
• Liquid 13 forms a surface 15 bordering region 14.
• the device is equipped with a detector meas- uring a parameter depending on the configuration of surface 15.
• This detector can be of various nature, and some embodiments thereof are explained in the following.
• the detector comprises a light source 16 placed on one side of con- tainer 10 as well was two light sensors 17, 18 placed on the other side of container 10. One of the detectors 17, 18 is closer to location 4 than the other.
• the light from light source 16 enters chamber 10 and passes through liquid 13 and through surface 15. At surface 15 the light is diffracted by some degree, then exits container 10 through top wall 11 and arrives at the light sensors 17 and 18.
• the circuit processing the signal from the light sensors 17, 18 is shown in Fig. 3. It comprises an operational amplifier 20, which measures the difference of the signals from light sensors 17 and 18.
• the output signal is fed to a feedback controller 21, such as a PID- , PI- or PD-controller, which tries to control actuator 5 in such a manner that the signal from amplifier 20 goes to zero.
• the device is further equipped with an output device 22, which e.g. displays the voltage used to con- trol actuator 5 or some other signal that is indicative of the tiling angle of movable carrier 2 in respect to support 1.
• Output device 22 can, in addition or alternatively to a display, e.g. comprise a digital interface for transferring the signal to an external system.
• the device Prior to a measurement, the device is set up such that the signals of both light sensors 17, 18 are approximately equal. Then, controller 21 is activated and tilts movable carrier 2, e.g. until the signals are ex- actly equal. In this position, light source 16, light sensors 17, 18 and surface 15 are symmetrical in respect to a vertical plane parallel to the device's tilt axis.
• tilting angle a depends on the mass M of body 24 and its distance r from chamber 10, in approximation, as follows:
• tilting angle ⁇ it is e.g. possible to determine the mass M or the distance r.
• a second embodiment of detector assembly 6 is shown in Fig. 4. It again comprises a light source 16, whose light this time enters top wall 11 of container 10 and is then reflected, at least partially, by surface 15.
• the two light sensors 17, 18 are positioned symmetrically in respect to the axis of light source 16 and measure two light beams reflected at opposite parts of surface 15.
• the signals from the light sensors 17, 18 are again proc- essed by a circuit as shown in Fig. 3.
• the device is again set up such that the signals of both light sensors 17, 18 are approximately equal and controller 21 is activated to tilt movable carrier 2 until the signals are exactly equal.
• controller 21 is activated to tilt movable carrier 2 until the signals are exactly equal.
• detector assembly 6 can comprise at least one light source that illuminates at least part of the liquid and at least one light sensor that detects light influenced by the liquid.
• the light can e.g. be diffracted or reflected at surface 15, or it can be partially absorbed or scattered by the liquid.
• the term "light”, in this respect, is to be understood in broad manner, and, in particular, encompasses infrared, visible and ultraviolet light.
• detector assembly 6 can, however, also carry out non-optical measurements as well.
• An example of a non-optical measurement is shown in Fig. 5.
• detector assembly 6 comprises two capacitors Cl, C2, each straddling container 10.
• Each capacitor comprises a first electrode mounted to top wall 11 of container 10 and a second electrode mounted to bot- torn wall 12 of container 10.
• Surface 15 is located at least partially within each capacitor, i.e. it extends into the space between the electrodes of each capacitor.
• the capacitance of each capacitor Cl, C2 depends on the configuration of the liquid 10.
• the capacitors Cl, C2 are arranged symmetrically to a vertical plane parallel to the device's tilt axis.
• Detector assembly 6 can also be adapted to measure a magnetic parameter depending on the configuration of the liquid.
• detector assembly 6 can be equipped with one or more coils. A corresponding embodiment is shown in Fig. 6.
• container 10 is a symmetrical, bent tube with two coils 25, 26 wound around opposite halves thereof.
• Surface 15 is located at least partially within each coil, i.e. it extends into the space enclosed by the coil's windings.
• Fig. 6 also shows a circuit for feeding a signal to controller 21. It comprises two oscillator cir- cuits 28, 29, whose frequencies fl and f2 are controlled by coils 25 and 26, respectively.
• a frequency comparator 30 generates a signal proportional to the difference fl - f2 and feeds the same to controller 21. Controller 21 strives to keep the output of comparator 30 zero (i.e. fl - f2) .
• the present device can also be used to carry out spatially resolved measurements if movable carrier 2 is movable about two tilt axes 32, 33 and if detector assembly 6 is equipped to detect rotations about each of these axes.
• Tilt axes 32, 33 are horizontal and perpendicular to each other.
• Detector assembly 6 can e.g. comprise two chambers and detectors of the type shown in Figs. 2 - 6, or it can contain a single chamber with detectors for detecting a change of configuration in both directions. In other words, detector assembly 6 measures a first and a second parameter depending on the tilting of carrier 2 about the first and the second tilt axis 32 and 33, re- spectively
• support 1 can be equipped with screws 36, 37, which allow a tilting of support 1 about axes parallel to the tilt axes 32 and 33, respectively. They can be used for a zero position adjustment of the device.
• a similar screw or set or screws can also be used in the embodiment of Fig. 1.
• the device advantageously measures two parameters depending differently (e.g. oppositely) on the configuration of liquid 13, and the feedback loop controller 21 strives to keep the parameters equal. This design allows to compensate for any drift that affects both measured parameters .
• the liquid 13 should have low viscosity. It can e.g. be an alcohol of low viscosity.
• liquid 13 can be a superfluid, in which case liquid 13 has to be kept at a suitable temperature .
• top wall 11 of container 10 was curved and convex.
• Top wall 11 can, however, also be flat and extend horizon- tally, in which case the location of region 14 becomes unstable and is highly sensitive to changes of the mass distribution around detector assembly 6.
• container 10 can be shaped such that two spaced-apart regions 14 of a second fluid or vacuum are formed, each having its own surface 15.
• cavity 10 can comprise two domes 40a, 40b interconnected by a duct 41, with the regions 14 formed at the top of each dome 40a, 40b.
• Duct 41 can have a comparatively small diameter for damping the motions of liquid 13.
• the two surfaces 15 are at equal height. If a mass is placed close to one of the domes 40a, 40b, the levels, i.e. the con- figurations, of the two surfaces 15 will change in opposite directions, which can be measured by a suitable sensor.
• a capacitive sensor which comprises a float 42 floating on each of the surfaces 15.
• Each float 42 carries a floating electrode 44 mounted on its top side.
• a pair of electrodes 46 is pro- vided.
• Each pair of electrodes 46 forms, together with floating electrode 44, a capacitor Cl or C2, respectively.
• the capacitors Cl, C2 each comprise an electrode (namely the floating electrodes 46) , whose position changes when the configu- ration of the liquid changes. If fluid 14 is electrically conductive, the one of the electrodes of each capacitor Cl, C2 can be formed by the fluid itself if the fluid is set to a defined electrical potential.
• Fig. 8 can also be combined with inductive or optical sensors as described in the other embodiments .
• Chamber 10 has been shown as a hermetically closed chamber in all the embodiments.
• a hermetically closed chamber is advantageous because it prevents an evaporation of liquid 13.
• chamber 10 can also be in communication with the environment.
• chamber 10 is substantially rigid.
• chamber 10 can also be flexible or elastic.
• it can be formed at least partially by a flexible or elastic membrane, e.g. a balloon, whose shape changes when the gravitational field varies. In this case, the position of the surface of the membrane can be measured.
• chamber 10 can be fully filled by the liquid. While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geophysics (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

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• 2008
  • 2008-01-28 WO PCT/CH2008/000027 patent/WO2009094787A1/en active Application Filing
  • 2008-01-28 EP EP08700532A patent/EP2243002A1/de not_active Withdrawn

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