GB2062237A - Conversion of a linear displacement to a time-dependent signal - Google Patents

Conversion of a linear displacement to a time-dependent signal Download PDF

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Publication number
GB2062237A
GB2062237A GB7933424A GB7933424A GB2062237A GB 2062237 A GB2062237 A GB 2062237A GB 7933424 A GB7933424 A GB 7933424A GB 7933424 A GB7933424 A GB 7933424A GB 2062237 A GB2062237 A GB 2062237A
Authority
GB
United Kingdom
Prior art keywords
frequency signal
displacement
transducer
proportional
indicating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB7933424A
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ELECTRONIC LAB Ltd
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ELECTRONIC LAB Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ELECTRONIC LAB Ltd filed Critical ELECTRONIC LAB Ltd
Priority to GB7933424A priority Critical patent/GB2062237A/en
Publication of GB2062237A publication Critical patent/GB2062237A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/2006—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils
    • G01D5/2013—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils by a movable ferromagnetic element, e.g. a core
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G7/00—Weighing apparatus wherein the balancing is effected by magnetic, electromagnetic, or electrostatic action, or by means not provided for in the preceding groups
    • G01G7/02—Weighing apparatus wherein the balancing is effected by magnetic, electromagnetic, or electrostatic action, or by means not provided for in the preceding groups by electromagnetic action

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

Method of and apparatus for measuring the linear displacement of an element (12) comprises using the movement to vary a parameter, for example the inductance, of a transducer (14, 16), producing therefrom a frequency signal whose period is proportional to the displacement, and using a microprocessor (20) to measure this period and drive an output display (24) for example a digital display. <IMAGE>

Description

SPECIFICATION Conversion of a linear displacement to a timedependent signal This invention relates generally to the conversion of a linear displacement into a timedependent signal, e.g. a frequency signal variable in dependence on the magnitude of the displacement.
Although this basic principle finds application in many different types of apparatus, equipment and machine, it is particularly applicable to weighing machines. Thus, the linear motion of an element of the machine which is displaceable as a function of an imposed weight can now be converted in accordance with the invention into a timedependent signal which can be measured by a microprocessor for example to provide a display output.
Many method are known of converting a linear displacement into a rotary motion, generally by purely mechanical means. Measuring devices which are intended to provide a visible output of a variable quantity and which incorporate such mechanisms often include a dial-and-pointer display. Such mechanisms tend to be bulky, are subject to frictional loads, tend to produce inaccurate measurements with increasing age, and require regular cleaning and maintenance.
It is an object of the present invention to provide a method and apparatus which overcomes these problems and which enables one to achieve speed, accuracy and reliability of output in a measuring device or instrument coupled with small size.
The present invention is applicable to a wide variety of machines, devices, instruments, etc.
Weighing machines represent one such class of machine, from small size models for weighing letters, kitchen scales, bathroom scales, etc. up to large size machines for weighing vehicles for example.
In accordance with the present invention there is provided a method of measuring the linear displacement of an element comprising the steps of using the movement of the element to vary a parameter of a transducer, producing from said transducer a frequency signal whose period is proportional to the displacement, and using said frequency signal to drive indicating and/or recording means to provide a measurement representative of said displacement.
Also in accordance with the invention there is provided apparatus for measuring the linear displacement of an element comprising a transducer, a parameter of which is arranged to be varied in proportional response to such displacement, said transducer being arranged to produce a frequency signal whose period is proportional to the displacement, and means responsive to said frequency signal to drive indicating and/or recording means to provide a measurement of said displacement.
Preferably, the method includes using the movement of the element to vary the inductance of an electromechanical transducer.
The transducer may comprise an annular coil connected to a source of electrical current, the displaceable element being movable axially within the coil and thereby varying its inductance.
Also in accordance with the invention there is provided a method of weighing comprising the steps of causing the imposition of a load to effect a corresponding linear displacement of an element, arranging that said displacement proportionally varies a parameter of a transducer, producing from said transducer a frequency signal whose period is proportional to the displacement, and using said frequency signal to drive indicating and/or recording means to provide a measurement indicative of the imposed load.
Also in accordance with the invention there is provided weighing apparatus comprising an element which is displaceable linearly in response to the imposition of a load to be measured, transducer means arranged to convert the linear motion into a frequency signal whose period is proportional to the displacement, weight indicating and/or recording means, and means responsive to said frequency signal to drive said indicating and/or recording means to provide a measurement indicative of the imposed load.
One preferred embodiment of weighing machine in accordance with the present invention will now be described by way of example and with reference to the accompanying drawing which is a block schematic diagram of the weighing machine with the construction of the transducer shown on an enlarged scale as an inset to the Figure.
Referring to the drawing, a scale-pan is indicated at 10 and forms part of the weighing machine. The scale-pan which is illustrated could be used for example for the weighing of letters, and it would have an equivalent load-displaceable part in any other weighing machine adapted for a different purpose. The bottom of the scale-pan 10 is provided with a rod 12, which is preferably a ferrite rod. The rod 12 forms a movable element of a transducer, part of which is shown in greater detail in the inset to the drawing, and which comprises a wound core 14 having a hollow centre within which the rod is linearly displaceable. Further reference to this transducer will be made later.
The coil 14 acts as a pick-up coil for an LC oscillator 1 6. The output of the oscillator 1 6 is connected to a counter 1 8 which constitutes the input of a microprocessor 20. A clock 22 is connected to the microprocessor 20, and it also has inputs to select the full scale deflection, the unit weight and tare weight. The microprocessor 20 is arranged to drive a four-digit display 24 in any desired units. The display may also include an indication of the units in which the weight is being displayed and/or of whether the weight is in excess of a predetermined value, i.e. is in an overload condition.
Referring again now to the transducer means, it will be appreciated that the inductance of the coil 14 is given by the formula: MN2A L = I where A = cross-sectional area of the coil N = number of turns t= length of the coil ,u = the permeability of the core.
At any position of the core 12 within the.coil 14 the total inductance can be regarded as the sum of two inductances in series, one under the influence of the ferrite rod 12 and the other having an air core. However, because the permeability of the ferrite rod is very much greater than the permeability of air, the total inductance can be regarded as equal to that part which is influenced by the ferrite rod only, provided that the core is well inside the coil in order to avoid end effects.
The inductor is used as the inductive element of the LC oscillator 16, the frequency of which is given by the formula:
However, L is proportional to n2, where n is the number of turns influenced by the ferrite rod 12.
Therefore fis proportional to n and hence the period of oscillation T is proportional to n.
However, if the coil 14 is wound uniformly, then n is proportional to the position of the rod 12 inside the coil 14. Therefore, for a long uniform coil with a high permeability rod which is longer than the coil and has its end positioned well away from the ends of the coil, the period of oscillation T is a linear measure of the movement of the rod 12.
One is therefore able to use the linear displacement of the rod attached to the scale-pan 10 as an input variable to the microprocessor which is representative of the load on the scale Qan.
vhe basic weighing machine as described above can pe modified in various ways. For example, it could also incorporate a timer, based upon the output from the clock 22, thus giving a product which is normally a digital clock but which can be used as a weighing machine when desired.
The invention is also applicable to a barometric instrument in order to be able to produce a digital read-out of pressure. The bellows of the instrument produces movements which are proportional to pressure changes, these movements are arranged to cause proportional movement of the ferrite rod 12, and this causes a measuring operation to be carried out, as described above. This is just one further example of the application of the principle embodied in the present invention.

Claims (14)

1. A method of measuring the linear displacement of an element comprising the steps of using the movement of the element to vary a parameter of a transducer, producing from said transducer a frequency signal whose period is proportional to the displacement, and using said frequency signal to drive indicating and/or recording means to provide a measurement representative of said displacement.
2. A method as claimed in claim 1 , which includes using the movements of the element to vary the inductance of an electro-mechanical transducer.
3. A method as claimed in claim 2, which includes an oscillator to produce said frequency signal.
4. A method as claimed in any preceding claim, which includes feeding the frequency signal to a microprocessor which controls said indicating and/or recording means.
5. A method as claimed in any preceding claim, in which the output measurement is displayed digitally.
6. A method of weighing comprising the steps of causing the imposition of a load to effect a corresponding linear displacement of an element, arranging that said displacement proportionally varies a parameter of a transducer, producing from said transducer a frequency signal whose period is proportional to the displacement, and using said frequency signal to drive indicating and/or recording means to provide a measurement indicative of the imposed load.
7. A method as claimed in claim 6, in which the frequency signal is fed to a microprocessor.
8. A method of measuring linear displacement substantially as hereinbefore described with reference to the accompanying drawing.
9. Apparatus for measuring the linear displacement of an element comprising a transducer, a parameter of which is arranged to be varied in proportional response to such displacement, said transducer being arranged to produce a frequency signal whose period is proportional to the displacement, and means responsive to said frequency signal to drive indicating and/or recording means to provide a measurement of said displacement.
10. Apparatus as claimed in claim 9, in which said transducer comprises an annular coil connected to a source of electrical current, the displaceable element being movable axially within the coil and thereby varying its inductance.
11. Apparatus as claimed in claim 10, in which the transducer includes an oscillator connected to said coil with the coil forming an inductive element thereof.
12. Apparatus as claimed in claim 9, 10 or 11, in which the means responsive to the frequency signal comprises a microprocessor.
13. Weighing apparatus comprising an element which is displaceable linearly in response to the imposition of a load to be measured, transducer means arranged to convert the linear motion into a frequency signal whose period is proportional to the displacement, weight indicating and/or recording means, and means responsive to said frequency signal to drive said indicating and/or recording means to provide a measurement indicative of the imposed load.
14. Apparatus as claimed in claim 13, which includes a microprocessor driving said indicating and/or recording means.
1 5. Apparatus as claimed in claim 13 or 14, in which the displaceable element is a ferrite rod and the transducer comprises an annular core whose inductance is varied by the movement of the rod therein.
1 6. Apparatus for measuring the linear displacement of an element substantially as hereinbefore described with reference to the accompanying drawing.
GB7933424A 1979-09-26 1979-09-26 Conversion of a linear displacement to a time-dependent signal Withdrawn GB2062237A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB7933424A GB2062237A (en) 1979-09-26 1979-09-26 Conversion of a linear displacement to a time-dependent signal

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7933424A GB2062237A (en) 1979-09-26 1979-09-26 Conversion of a linear displacement to a time-dependent signal

Publications (1)

Publication Number Publication Date
GB2062237A true GB2062237A (en) 1981-05-20

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GB7933424A Withdrawn GB2062237A (en) 1979-09-26 1979-09-26 Conversion of a linear displacement to a time-dependent signal

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2507775A1 (en) * 1981-06-15 1982-12-17 Tanita Seisakusho Kk INDUCTION TYPE ELECTRONIC WEIGHING APPARATUS
FR2532080A1 (en) * 1982-08-13 1984-02-24 Bally Mfg Corp POSITION TRANSDUCER, INPUT DEVICE FOR PLAYER, POSITION TRANSDUCER SYSTEM AND VIDEOJEU
GB2137353A (en) * 1983-03-25 1984-10-03 Nl Industries Inc Method and apparatus for locating the stuck point of a pipe in a borehole
EP0127494A1 (en) * 1983-04-21 1984-12-05 Regie Nationale Des Usines Renault Device for assisting the economical operation of a vehicle comprising a thermal motor, in particular for an agricultural tractor
US4685678A (en) * 1982-08-13 1987-08-11 Bally Manufacturing Corporation Position transducer system for a joystick
GB2213594A (en) * 1987-12-09 1989-08-16 Herion Werke Kg Apparatus for measuring the position of the armature of a coil-and-armature magnetic device
GB2219404A (en) * 1988-05-20 1989-12-06 Zvl Vyzk Ustav Pro Valiva Differential inductance transducer circuit
EP0368128A2 (en) * 1988-11-02 1990-05-16 Daimler-Benz Aktiengesellschaft Circuit for an inductive sensor
EP0554952A1 (en) * 1992-02-06 1993-08-11 Peekel Instruments B.V. Extensometer
FR2710406A1 (en) * 1993-09-20 1995-03-31 Bosch Gmbh Robert Angle of rotation transmitter.
DE102007037216A1 (en) 2007-08-07 2009-02-12 Robert Bosch Gmbh Spooling device for use in measuring device, has carrier plates insulating against each other by insulating layer, and wire windings assigned to spool on different carrier plates and electrically connected with each other

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2507775A1 (en) * 1981-06-15 1982-12-17 Tanita Seisakusho Kk INDUCTION TYPE ELECTRONIC WEIGHING APPARATUS
FR2532080A1 (en) * 1982-08-13 1984-02-24 Bally Mfg Corp POSITION TRANSDUCER, INPUT DEVICE FOR PLAYER, POSITION TRANSDUCER SYSTEM AND VIDEOJEU
US4685678A (en) * 1982-08-13 1987-08-11 Bally Manufacturing Corporation Position transducer system for a joystick
GB2137353A (en) * 1983-03-25 1984-10-03 Nl Industries Inc Method and apparatus for locating the stuck point of a pipe in a borehole
EP0127494A1 (en) * 1983-04-21 1984-12-05 Regie Nationale Des Usines Renault Device for assisting the economical operation of a vehicle comprising a thermal motor, in particular for an agricultural tractor
GB2213594B (en) * 1987-12-09 1992-01-02 Herion Werke Kg Apparatus for measuring the position of the armature of a coil and armature magnetic device
GB2213594A (en) * 1987-12-09 1989-08-16 Herion Werke Kg Apparatus for measuring the position of the armature of a coil-and-armature magnetic device
GB2219404A (en) * 1988-05-20 1989-12-06 Zvl Vyzk Ustav Pro Valiva Differential inductance transducer circuit
EP0368128A2 (en) * 1988-11-02 1990-05-16 Daimler-Benz Aktiengesellschaft Circuit for an inductive sensor
EP0368128A3 (en) * 1988-11-02 1991-07-03 Daimler-Benz Aktiengesellschaft Circuit for an inductive sensor
EP0554952A1 (en) * 1992-02-06 1993-08-11 Peekel Instruments B.V. Extensometer
FR2710406A1 (en) * 1993-09-20 1995-03-31 Bosch Gmbh Robert Angle of rotation transmitter.
DE102007037216A1 (en) 2007-08-07 2009-02-12 Robert Bosch Gmbh Spooling device for use in measuring device, has carrier plates insulating against each other by insulating layer, and wire windings assigned to spool on different carrier plates and electrically connected with each other
DE102007037216B4 (en) 2007-08-07 2023-01-19 Robert Bosch Gmbh Measuring device for non-contact detection of a relative position

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