CA2130193A1 - Displacement/force transducers utilizing hall effect sensors - Google Patents
Displacement/force transducers utilizing hall effect sensorsInfo
- Publication number
- CA2130193A1 CA2130193A1 CA002130193A CA2130193A CA2130193A1 CA 2130193 A1 CA2130193 A1 CA 2130193A1 CA 002130193 A CA002130193 A CA 002130193A CA 2130193 A CA2130193 A CA 2130193A CA 2130193 A1 CA2130193 A1 CA 2130193A1
- Authority
- CA
- Canada
- Prior art keywords
- mass
- displacement
- beams
- masses
- hall effect
- 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.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
-
- 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
- G01D5/142—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 using Hall-effect devices
- G01D5/145—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 using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/105—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by magnetically sensitive devices
Abstract
A device for measuring displacement and force comprises two masses of material linked together by a parallel beam linkage which permits displacement of one mass relative to the other in a single direction. The displacement or force input to be measured is applied to one of the masses in the allowable direction. The displacement of the masses with respect to each other is sensed by a sensor. In a preferred embodiment, the sensor comprises a Hall effect sensor attached to one of the masses positioned between two magnets attached to the other mass. Movement of one mass relative to the other changes the magnetic field around the Hall effect sensor. The change is sensed by the Hall effect sensor.
Description
WO93/18380 ~ 3 PCT/US93/01755 Displacement/Force Transducers Utilizinq Hall Effect Sensors Backqround of th~ Invention In many environments, accurate and precise measurements are required of small positional displacements of objects within mechanical systems. It `
is also often req~ired to obtain measurements of force applied in a particular direction.
, Most mechanical devices designed to obtain these measurements are typically limited by the inherent characteristics Gf mechanical systems. These limitations incl~de hysteresis and backlash. Also, forces- and displ~^ements are rarely limited in application to orly a single direction. A force or lS displacement app~ied in primarily the z direction, for examp~e, will alsio have components -n both the x and y directions. In ~.ddition, x, y, and z torsional components will also be present. If it ls desired to obtain an accurate measurement of the displacement or force in the z di:ection only, the effect of these additional componi~ints must be minimized in the measurement device.
Summary of the Invention The present invention provides a device for measuring displaoement. The device comprises two masses of matericl linked together via two parallel beams. The beam~ are configured so as to allow the two masses to move w:th respect to each other in a direction transv~rse to the beams against a return force provided by the beams. Motior. in other directions between the masses is virtually eliminated by the parallel heam configuration. A sensor is used WO93/18380 PCT/US93/0175~ ~
~U~3 to sense the displacement of the masses relative to each other.
One mass may be located within the other mass. In this configuration, the masses and the parallel beams linkin~ them may form a single unit formed from a single piece of material.
The beams mcy each consist of a piece of material wrapped around it~elf to form the beam into a spring member. This may be accomplished by cutting the masses and the fold-bac}- spring beams from a single piece of material.
The device may also be used as a force transducer.
With the spring characteristics of the linkage known, th~ displacement measurement provides an indication of the force applied to ~ne of the masses. Thus, various ranges of force can be measured by using different spring members ir the linkage.
The device may also be used as an inclination transducer. Witi the masses being of known mass and the beams having a known spring constant, the displacement meac~rement provides ar. indication of the angle of inclination of the device.
In the preferred embodiment of the invention, the sensor cumprises a Hall effect sensor positioned between two magn~ts. The Hall effect sensor is fixed to the first mass. The two magnets are fixed to the second mass with one magnet on either side of the Hall effect sensor. Thus, the Hall effect sensor is positioned in the magnetic field within the gap between the two magnets. When the second mass is displaced with respect to the first mass, the Hall effect sensor W093/18380 ~V ~ 9 ~ PC~/US93/Ot755 detects the resu~ting change in the magnetic field and outputs a signal indicative of the amount of displacement.
Brief Descriptio~: of the Drawinqs The foregoing and other objects, features and ~:
advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying dra~ings in which like reference characters refer lo the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles oi the invention.
Figure 1 schematically depicts a prior art configuration of two masses and parallel beams.
Figure 2 shows the masses and the parallel beam linkage cut from a single piece of material in the preferred embodir.~ent.
Figure 3 depicts the details of the fold-back feature of the parallel beams and the parameters used in the displacement equation for the device~
Figure 4 shows the preferred embodiment of the invention.
Figure 5 is a sectional view of the preferred embodiment.
Figure 6 is ~n isometric view of the preferred embodiment.
Figure 7 is ~ block diagram of the electronics of the preferred em~odiment.
~ ~ ~ 9 3 Detailed Descri~tion ~f the Invention Figure 1 sc~ematically depicts a prior art configuration of two masses 12 and 14 side-by-side linked by parallel beams 18 and 20. Mass 12 is linked to mass 14 via parallel beam linkage 16. Mass 12 is considered stationary, and mass 14 is movable. Linkage 16 is comprised cf two parallel beams 18 and 20. The beams 18, 20 are fixed at their ends to masses 12, 14.
They allow mass 14 to move in the ~z direction in response to a force or displacement input 15 while remaining rigid to movement of mass 14 in any other direction. The b2ams 18, 20 also provide a reactive force against the force or dis~lacement input 15 such that when the input 1~ is removed, mass 14 returns to its original position. The linkage 16 thus allows lateral mo~ement of mass 14 relative to mass 12 while minimizing movem~t in other directions.
A force or c~.isplacement input 15 applied in the z axis to mass 14 causes mass 14 to move in the z axis.
Beams 18 and 20 are configured to pr~vide a spring force against that mo~ement~ Also, they are rigid to any movement in the other axes. Therefore, they allow motion of mass 1~ in only one direction while eliminating most motion in other dilections.
One form of motion not eli~inated by the c:onf iguration of ~igure 1 is motion of the masses 12, 14 toward each other when the input 15 is appl ied .
When mass 14 is forced down, each of beams 18 and 20 bends into a slic~t "S" shape. This causes the ends of 3~ the beams 18 and 20 attached to mass 14 to translate W093/]8380 PCT/US93/017 along an arc as indicated by the dotted arcs in Figure 1 (shown exaggerated for clarity). Since the ends of the beams 18, 20 arc, so will the ma~s 14 to which they are fixed. Due to this arc motion, there will be some displacement of m~ss 14 with respect to mass 12 in the y directio~.
Figure 2 sh~ws in cross section the masses 12 and 14 and the linka~e 16 in the preferred embodiment of the invention. The body of the transducer 10 serves as stationary mass ~ from Figure 1. In one specific embodiment, the ~ody is a rectangular block 1.25 inche~
high, 2.37 inchec wide and one inch deep. In the preferred embodiment, the movable mass 14 is located within mass 12. 'rhe linkage 16 is comprised of beams 18 and 20. The ~eams lB, 20 are produced in a i'fold-back" spring conliguration, the details of which will be discussed belcw. Both masses 12 and 14 and the linkage 16 are ct~t from a single piece of material using wire elect~ical-discharqe mac~ning (EDM~
techniques. Slots 24 and 26 define mass 12 and mass 14 and make up part of linkage 16. Slc~ts 28 and 30 complete the linkage 16. Slots 24 and 28 form beam 18, and slots 26 and 30 form beam 20. ~isplacement or force input 15 is applied to mass 14 via an opening in mass 12, not sho~n.
The parallel beam linkage 16 between the masses is detailed in Figu~e 3. In this embodiment, each beam is comprised of two arms in a fold-back configuration. As an example, beam 18 is comprised of arms 70 and 72 displaced relati~e to each other transverse to the beam structure itself. The arms 70 and 72 are joined end-WO93/18380 PCT/US93/0175~
to-end. The fol-back design of th~ beams 1~, 20 effected by slot~ 24, 26, 28, and 30, provides the preferred embodiment with unique advantages. The fold-back of the beams 18, 20 minimizes displacement of mass 14 in the y axis. To illustrate, if a displacement or force input 15 is applied in the direction indicated by arrow 23 in Figure 3, mass 14 will move in that direction. Beam 18 will expand as arms 70 and 72 move away from each other. At the same time, beam 20 will compress as arms 74 and 76 move toward each other.
The motion cf the individual arms within a beam operates to eliminate motion of mass 14 in the y direction. As t~e input 15 forces mass 14 down, arm 70 bends in the sli~ht "S" shape discussed above with reference to Figure 1. The end of arm 70 arcs as indicated by dotted arrow 73. This arc tends to translate the end of the arm 70 to the left. However, at the same time, arm 72 also bends into the S shape, and the end of a~-.n 72 arcs as indic~ted by dotted arrow 71. This motion tends to translate the end of arm 72 to the right. Tiese two approximately equal and opposite motions tend to cancel each other out. Thus, the top of the mass 14 moves only in the z direction.
The bottom of th~ mass 14 is prevented from moving in the y direction :n the same manner ky beam 20. Arm 76 arcs as indicate~ by dotted arrow 7', tending to move mass 14 to the right. Arm 74 arcs as indicated by dotted arrow 77, tending to move mass 14 to the left, thus cancelling out the motion to the right. Thus, beams 18 and 20 configured as fold-back springs act in concert to eliminate motion of mass 14 in the y direction.
~1301~3 The unitary ~ass and beam design provides the transducer 10 with additional featu~es. The transducer 10 may be made cc~pact because the fold-back design provides for mor~ desired spring length in a small space. ~lso, because the masses 12, 14 and the beams 18, 20 are made from one piece of material, hysteresis-free motion can ~.~2 achieved. As noted above, there is essentially no s.de motion between the masses 12, 14.
Also, the motion is directly and linearly proportional to force along the z axis.
Slots 24, 26, 28, 30 of the unitary design also provide extremely high force overload protection:for the transducer. A force or displacement input 15 beyond the displa~ement range of the transducer simply 15 causes mass 14 to bump against surface 32 or 34 when slot 24 or 26, respectively, closes. Thus, the single piec~ configurat:on of the preferred embodiment - provi.des displacement stops to prevent overload of the transducer 10.
Also, due to the one-piece design of the invention, very high tension or compression loads applied to mass 14 will not damage the transducer 10.
The side load (Fx, Fy) capacity and the three torsional (M~, My~ M2) capa~.ties axe substantial and depend upon the load range of the transducer 10. The load range can be ~aried by ~hanging the characteristics of the parallel beams 18, 20 as discussed below.
Figure 4 sh~ws the preferred embodiment displacem~nt and force transducer 10. Displacement sensor 22 comprises two magnets 38 and 40 on opposite sides of a Hall ~ffect sensor 42. The Hall effect sensor 42 is mounted on a printed circuit board 44 which is mounted on the transducer body 12 in grooves 17 (see Figure 2). Magnet holders 46 and 48 are press fit into mass 14. Magnets 38 and 40 are mounted on magnet holders 4~ and 48, respectively, with like poles facing each other, and Hall effect sensor 42 is positioned at the midpoint of the gap between the magnets 38, 40. rhe magnetic ~rrangement produces a , magnetic field w~.ich is zero in the center of t:he gap between the magnets 38, 40 and whic~ varies linearly in the direction per?endicular to the faces of the magnets 38, 40. The char.ge in field for motion parallel to the gap is small for 3apis less than one-half the magnet diameter and mot:~.ons of less than one-half the gap spacing.
Displacement or force input 15 at contact point 50 or S2 is transmitted to mass 14 through magnet holders 46 or 48. Displacement of magnets 38, 40 causes a change in the mag~etic field in the gap between the magnets 38, 40. The Hall effect sensor 42 senses the change in magnet~c field and genera';es a signal indicative of the change. This signal is transmitted to the circuitry on the printed circuit board 44. The circuitry condit;ons the signal and provides a bipolar output signal which is indicative of the displacement of mass 14.
Figure 5 is a sectional view (~A) of the transducer 10 cut as shown in Figure 4. Covers 80 and 82 enclose the assembly. This view shows the Hall effect sens~r 42 on the circuit board 44 mounted between the maqnets 38 and 40. It can be seen that ~13~53 displacement of mass 14 will displace the magnets 3~
and 40. This will cause a change in the magnetic field around the board ~4 which will be sensed by the Hall effect sensor 42.
Figure 6 is ~n isometric view of the preferred embodiment of the transducer 10. Th~ covers 80 and 82 have been remove~. Contact point 50 is shown threaded into magnet hold~ 46. This contact point 50 can be removed and exc~cnged for different types of contact points 50~ Seal 90 seals the transducer from environmental cortaminants. Seal retainer 92 holds the seal 90 in place. Magnet 38 is shown attached to magnet holder 46 and is located directly above the Hall effect sensor 42 on the circuit boa,~ 44.
When attached, covers ~0 and 82 seal the transducer 10. C~ver 82 attaches to the transducer via alignment pins 9~ pressed into alignment holes 106 (not shown). Alignmel~ pins 94 pass through clearance holes 102 in the body. The pins 94 are pressed into holes 106 in cover 80 1o enclose the trancducer 10. Seal 96 on cover 82 and ~eal 98 on cover B0 ~ontact the transducer body t~ seal out environmental contaminants, When the transducer 10 is assembled, clearance holes 100 in the coverc 80, 8~ and 104 in the body provide clearance for hardware to mount the transducer 10 (not shown). Access ~oles 108 and 110 provide access to screwdriver-adjustable potentiomete~s 88 and 86 on the circuit board 4~, respectively (see Figure 4).
Figure 7 is a block diagram of the electronic circuitry on pri~ted circuit board 44. A single-ended DC power supply (not sh~wn) provides a DC voltage ~13i)i.'~3 between ~lo and -~30 volts to a +8 VDC preregulator 54.
The +8 VDC outpul of preregulator 54 is provided to ~5 VDC regulator 56. The output of res~lator 56 powers the Hall effect c.ensor 42. The sensor 42 provides an output to amplifier 58 based upon the intensity of the magnetic field surrounding the sensor 42. In the preferred embodil.~ent, a +0.010 inch displacement of mass 14 will cauCe an approximate +200 Gauss deviation in magnetic field around the sensor 42. This corresponds to a +0.3 volt change in sensor 42 output.
DC/DC converter ~.0 converts the +8 ~JDC from the preregulator 54 to +15 VDC to power the amplifier 58.
The +0.3 volt output from the Hall effect sensor 42 is amplified to a ~:Ø0 volt output from the electronic circuitry.
Gain and balance control 62 allows the user to adjust the output of the transducer 10 via screwdriver-adjustable potentiometers 86 and 88 tsee Figure 4) accessible throush holes in the transducer cover 80.
The gain of amplifier 58 may be adjusted via potentiometer 86 so that the range of the output ma~ be varied~ For example, the user may require the output to swing between +5 volts instead of +10 volts. The other control acoessible to the user is the zero balance of the urit. Ordinarily, a zero displacement will yield a zerc output, and the voltage output will vary symmetrical:y on either side of zero volts as the displacement var:es on either side ~` zero inches.
However, in some applications it may be desirable to set the zero balnce such that zero displacement yields a non-zero voltage output. This may occur where more WO93/18380 PCT/USg3/01755 U~ 93 displacement is expected in one direction than in the other. This setting may be accomplished by the user via adjustable pc)-entiometer 88.
The displac~ment and force transducer 10 of the present inventior can be used for many different load ranges. The maximum displacement of the transducer 10 is set at +0.010 inch with +0.006 inch of overtravel.
The force requir~ to produce this rull scale displacement can be varied between about 10 grams and about 20 pounds. The full scale fo~ce for the transducer 10 is ~etermined by the spring characteristics of the linkage 16. This can be seen by referring back to Figure 3 which shows the details of the linkage 16. By substitutin~ the required displacement of C.010 inch for Z and the desired full-scale load range for F in the equation, one can solve for the required oeam parameters. Thus, the desired load ranqe for the transducer 10 de_ermines the dimensions of th~ components of the beams 18, ~o.
When a very low load range is celected, the transducer 10 caI) be used as an inclinometer. In this configuration, t}e contact points 5~, 52 are removed, and the access hcles to the mass 14 are capped off. In the inclinometer mode, the weight of mass 14 provides sufficient force '.o displace itself against the springmembers 18, 20 of linkage 16. The closer the displacement axic is to vertical, the greater the displacement. T}us, the amount of displacement of mass 14 provides an ir.dication of the angle of inclination of the transduce~ 10. The angle of inclination ~ of WO93/18380 PCT/US93~017~5 i93 the axis of disp~cement from vertical may be calculated by cos~'[ mg]
kx where m = mass of mass 14, . g = acce~eration due to gravity, k = sprir:g constant of the linkage 16, and x = displacement of mass 14.
A similar device can serve as an aecelerometer for accelerations in the z direction.
While this ~.nvention has been particularly shown and described wilh references to preferred embodiments thereof, it will ~e understood by those skilled in the art that various changes in form and details may be made therein without department from the spirit and scope of the invention as defined by the appended claims.
For example~. the first mass need not completely enclose the secord mass. The first mass ~ay simply wrap around the ~econd mass in any direction. Also, the second mass r;ay be located above or below or next to the first mas~. Regarding the beam configuration, the fold-back may comprise more than a single fold.
What is cla~med is:
is also often req~ired to obtain measurements of force applied in a particular direction.
, Most mechanical devices designed to obtain these measurements are typically limited by the inherent characteristics Gf mechanical systems. These limitations incl~de hysteresis and backlash. Also, forces- and displ~^ements are rarely limited in application to orly a single direction. A force or lS displacement app~ied in primarily the z direction, for examp~e, will alsio have components -n both the x and y directions. In ~.ddition, x, y, and z torsional components will also be present. If it ls desired to obtain an accurate measurement of the displacement or force in the z di:ection only, the effect of these additional componi~ints must be minimized in the measurement device.
Summary of the Invention The present invention provides a device for measuring displaoement. The device comprises two masses of matericl linked together via two parallel beams. The beam~ are configured so as to allow the two masses to move w:th respect to each other in a direction transv~rse to the beams against a return force provided by the beams. Motior. in other directions between the masses is virtually eliminated by the parallel heam configuration. A sensor is used WO93/18380 PCT/US93/0175~ ~
~U~3 to sense the displacement of the masses relative to each other.
One mass may be located within the other mass. In this configuration, the masses and the parallel beams linkin~ them may form a single unit formed from a single piece of material.
The beams mcy each consist of a piece of material wrapped around it~elf to form the beam into a spring member. This may be accomplished by cutting the masses and the fold-bac}- spring beams from a single piece of material.
The device may also be used as a force transducer.
With the spring characteristics of the linkage known, th~ displacement measurement provides an indication of the force applied to ~ne of the masses. Thus, various ranges of force can be measured by using different spring members ir the linkage.
The device may also be used as an inclination transducer. Witi the masses being of known mass and the beams having a known spring constant, the displacement meac~rement provides ar. indication of the angle of inclination of the device.
In the preferred embodiment of the invention, the sensor cumprises a Hall effect sensor positioned between two magn~ts. The Hall effect sensor is fixed to the first mass. The two magnets are fixed to the second mass with one magnet on either side of the Hall effect sensor. Thus, the Hall effect sensor is positioned in the magnetic field within the gap between the two magnets. When the second mass is displaced with respect to the first mass, the Hall effect sensor W093/18380 ~V ~ 9 ~ PC~/US93/Ot755 detects the resu~ting change in the magnetic field and outputs a signal indicative of the amount of displacement.
Brief Descriptio~: of the Drawinqs The foregoing and other objects, features and ~:
advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying dra~ings in which like reference characters refer lo the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles oi the invention.
Figure 1 schematically depicts a prior art configuration of two masses and parallel beams.
Figure 2 shows the masses and the parallel beam linkage cut from a single piece of material in the preferred embodir.~ent.
Figure 3 depicts the details of the fold-back feature of the parallel beams and the parameters used in the displacement equation for the device~
Figure 4 shows the preferred embodiment of the invention.
Figure 5 is a sectional view of the preferred embodiment.
Figure 6 is ~n isometric view of the preferred embodiment.
Figure 7 is ~ block diagram of the electronics of the preferred em~odiment.
~ ~ ~ 9 3 Detailed Descri~tion ~f the Invention Figure 1 sc~ematically depicts a prior art configuration of two masses 12 and 14 side-by-side linked by parallel beams 18 and 20. Mass 12 is linked to mass 14 via parallel beam linkage 16. Mass 12 is considered stationary, and mass 14 is movable. Linkage 16 is comprised cf two parallel beams 18 and 20. The beams 18, 20 are fixed at their ends to masses 12, 14.
They allow mass 14 to move in the ~z direction in response to a force or displacement input 15 while remaining rigid to movement of mass 14 in any other direction. The b2ams 18, 20 also provide a reactive force against the force or dis~lacement input 15 such that when the input 1~ is removed, mass 14 returns to its original position. The linkage 16 thus allows lateral mo~ement of mass 14 relative to mass 12 while minimizing movem~t in other directions.
A force or c~.isplacement input 15 applied in the z axis to mass 14 causes mass 14 to move in the z axis.
Beams 18 and 20 are configured to pr~vide a spring force against that mo~ement~ Also, they are rigid to any movement in the other axes. Therefore, they allow motion of mass 1~ in only one direction while eliminating most motion in other dilections.
One form of motion not eli~inated by the c:onf iguration of ~igure 1 is motion of the masses 12, 14 toward each other when the input 15 is appl ied .
When mass 14 is forced down, each of beams 18 and 20 bends into a slic~t "S" shape. This causes the ends of 3~ the beams 18 and 20 attached to mass 14 to translate W093/]8380 PCT/US93/017 along an arc as indicated by the dotted arcs in Figure 1 (shown exaggerated for clarity). Since the ends of the beams 18, 20 arc, so will the ma~s 14 to which they are fixed. Due to this arc motion, there will be some displacement of m~ss 14 with respect to mass 12 in the y directio~.
Figure 2 sh~ws in cross section the masses 12 and 14 and the linka~e 16 in the preferred embodiment of the invention. The body of the transducer 10 serves as stationary mass ~ from Figure 1. In one specific embodiment, the ~ody is a rectangular block 1.25 inche~
high, 2.37 inchec wide and one inch deep. In the preferred embodiment, the movable mass 14 is located within mass 12. 'rhe linkage 16 is comprised of beams 18 and 20. The ~eams lB, 20 are produced in a i'fold-back" spring conliguration, the details of which will be discussed belcw. Both masses 12 and 14 and the linkage 16 are ct~t from a single piece of material using wire elect~ical-discharqe mac~ning (EDM~
techniques. Slots 24 and 26 define mass 12 and mass 14 and make up part of linkage 16. Slc~ts 28 and 30 complete the linkage 16. Slots 24 and 28 form beam 18, and slots 26 and 30 form beam 20. ~isplacement or force input 15 is applied to mass 14 via an opening in mass 12, not sho~n.
The parallel beam linkage 16 between the masses is detailed in Figu~e 3. In this embodiment, each beam is comprised of two arms in a fold-back configuration. As an example, beam 18 is comprised of arms 70 and 72 displaced relati~e to each other transverse to the beam structure itself. The arms 70 and 72 are joined end-WO93/18380 PCT/US93/0175~
to-end. The fol-back design of th~ beams 1~, 20 effected by slot~ 24, 26, 28, and 30, provides the preferred embodiment with unique advantages. The fold-back of the beams 18, 20 minimizes displacement of mass 14 in the y axis. To illustrate, if a displacement or force input 15 is applied in the direction indicated by arrow 23 in Figure 3, mass 14 will move in that direction. Beam 18 will expand as arms 70 and 72 move away from each other. At the same time, beam 20 will compress as arms 74 and 76 move toward each other.
The motion cf the individual arms within a beam operates to eliminate motion of mass 14 in the y direction. As t~e input 15 forces mass 14 down, arm 70 bends in the sli~ht "S" shape discussed above with reference to Figure 1. The end of arm 70 arcs as indicated by dotted arrow 73. This arc tends to translate the end of the arm 70 to the left. However, at the same time, arm 72 also bends into the S shape, and the end of a~-.n 72 arcs as indic~ted by dotted arrow 71. This motion tends to translate the end of arm 72 to the right. Tiese two approximately equal and opposite motions tend to cancel each other out. Thus, the top of the mass 14 moves only in the z direction.
The bottom of th~ mass 14 is prevented from moving in the y direction :n the same manner ky beam 20. Arm 76 arcs as indicate~ by dotted arrow 7', tending to move mass 14 to the right. Arm 74 arcs as indicated by dotted arrow 77, tending to move mass 14 to the left, thus cancelling out the motion to the right. Thus, beams 18 and 20 configured as fold-back springs act in concert to eliminate motion of mass 14 in the y direction.
~1301~3 The unitary ~ass and beam design provides the transducer 10 with additional featu~es. The transducer 10 may be made cc~pact because the fold-back design provides for mor~ desired spring length in a small space. ~lso, because the masses 12, 14 and the beams 18, 20 are made from one piece of material, hysteresis-free motion can ~.~2 achieved. As noted above, there is essentially no s.de motion between the masses 12, 14.
Also, the motion is directly and linearly proportional to force along the z axis.
Slots 24, 26, 28, 30 of the unitary design also provide extremely high force overload protection:for the transducer. A force or displacement input 15 beyond the displa~ement range of the transducer simply 15 causes mass 14 to bump against surface 32 or 34 when slot 24 or 26, respectively, closes. Thus, the single piec~ configurat:on of the preferred embodiment - provi.des displacement stops to prevent overload of the transducer 10.
Also, due to the one-piece design of the invention, very high tension or compression loads applied to mass 14 will not damage the transducer 10.
The side load (Fx, Fy) capacity and the three torsional (M~, My~ M2) capa~.ties axe substantial and depend upon the load range of the transducer 10. The load range can be ~aried by ~hanging the characteristics of the parallel beams 18, 20 as discussed below.
Figure 4 sh~ws the preferred embodiment displacem~nt and force transducer 10. Displacement sensor 22 comprises two magnets 38 and 40 on opposite sides of a Hall ~ffect sensor 42. The Hall effect sensor 42 is mounted on a printed circuit board 44 which is mounted on the transducer body 12 in grooves 17 (see Figure 2). Magnet holders 46 and 48 are press fit into mass 14. Magnets 38 and 40 are mounted on magnet holders 4~ and 48, respectively, with like poles facing each other, and Hall effect sensor 42 is positioned at the midpoint of the gap between the magnets 38, 40. rhe magnetic ~rrangement produces a , magnetic field w~.ich is zero in the center of t:he gap between the magnets 38, 40 and whic~ varies linearly in the direction per?endicular to the faces of the magnets 38, 40. The char.ge in field for motion parallel to the gap is small for 3apis less than one-half the magnet diameter and mot:~.ons of less than one-half the gap spacing.
Displacement or force input 15 at contact point 50 or S2 is transmitted to mass 14 through magnet holders 46 or 48. Displacement of magnets 38, 40 causes a change in the mag~etic field in the gap between the magnets 38, 40. The Hall effect sensor 42 senses the change in magnet~c field and genera';es a signal indicative of the change. This signal is transmitted to the circuitry on the printed circuit board 44. The circuitry condit;ons the signal and provides a bipolar output signal which is indicative of the displacement of mass 14.
Figure 5 is a sectional view (~A) of the transducer 10 cut as shown in Figure 4. Covers 80 and 82 enclose the assembly. This view shows the Hall effect sens~r 42 on the circuit board 44 mounted between the maqnets 38 and 40. It can be seen that ~13~53 displacement of mass 14 will displace the magnets 3~
and 40. This will cause a change in the magnetic field around the board ~4 which will be sensed by the Hall effect sensor 42.
Figure 6 is ~n isometric view of the preferred embodiment of the transducer 10. Th~ covers 80 and 82 have been remove~. Contact point 50 is shown threaded into magnet hold~ 46. This contact point 50 can be removed and exc~cnged for different types of contact points 50~ Seal 90 seals the transducer from environmental cortaminants. Seal retainer 92 holds the seal 90 in place. Magnet 38 is shown attached to magnet holder 46 and is located directly above the Hall effect sensor 42 on the circuit boa,~ 44.
When attached, covers ~0 and 82 seal the transducer 10. C~ver 82 attaches to the transducer via alignment pins 9~ pressed into alignment holes 106 (not shown). Alignmel~ pins 94 pass through clearance holes 102 in the body. The pins 94 are pressed into holes 106 in cover 80 1o enclose the trancducer 10. Seal 96 on cover 82 and ~eal 98 on cover B0 ~ontact the transducer body t~ seal out environmental contaminants, When the transducer 10 is assembled, clearance holes 100 in the coverc 80, 8~ and 104 in the body provide clearance for hardware to mount the transducer 10 (not shown). Access ~oles 108 and 110 provide access to screwdriver-adjustable potentiomete~s 88 and 86 on the circuit board 4~, respectively (see Figure 4).
Figure 7 is a block diagram of the electronic circuitry on pri~ted circuit board 44. A single-ended DC power supply (not sh~wn) provides a DC voltage ~13i)i.'~3 between ~lo and -~30 volts to a +8 VDC preregulator 54.
The +8 VDC outpul of preregulator 54 is provided to ~5 VDC regulator 56. The output of res~lator 56 powers the Hall effect c.ensor 42. The sensor 42 provides an output to amplifier 58 based upon the intensity of the magnetic field surrounding the sensor 42. In the preferred embodil.~ent, a +0.010 inch displacement of mass 14 will cauCe an approximate +200 Gauss deviation in magnetic field around the sensor 42. This corresponds to a +0.3 volt change in sensor 42 output.
DC/DC converter ~.0 converts the +8 ~JDC from the preregulator 54 to +15 VDC to power the amplifier 58.
The +0.3 volt output from the Hall effect sensor 42 is amplified to a ~:Ø0 volt output from the electronic circuitry.
Gain and balance control 62 allows the user to adjust the output of the transducer 10 via screwdriver-adjustable potentiometers 86 and 88 tsee Figure 4) accessible throush holes in the transducer cover 80.
The gain of amplifier 58 may be adjusted via potentiometer 86 so that the range of the output ma~ be varied~ For example, the user may require the output to swing between +5 volts instead of +10 volts. The other control acoessible to the user is the zero balance of the urit. Ordinarily, a zero displacement will yield a zerc output, and the voltage output will vary symmetrical:y on either side of zero volts as the displacement var:es on either side ~` zero inches.
However, in some applications it may be desirable to set the zero balnce such that zero displacement yields a non-zero voltage output. This may occur where more WO93/18380 PCT/USg3/01755 U~ 93 displacement is expected in one direction than in the other. This setting may be accomplished by the user via adjustable pc)-entiometer 88.
The displac~ment and force transducer 10 of the present inventior can be used for many different load ranges. The maximum displacement of the transducer 10 is set at +0.010 inch with +0.006 inch of overtravel.
The force requir~ to produce this rull scale displacement can be varied between about 10 grams and about 20 pounds. The full scale fo~ce for the transducer 10 is ~etermined by the spring characteristics of the linkage 16. This can be seen by referring back to Figure 3 which shows the details of the linkage 16. By substitutin~ the required displacement of C.010 inch for Z and the desired full-scale load range for F in the equation, one can solve for the required oeam parameters. Thus, the desired load ranqe for the transducer 10 de_ermines the dimensions of th~ components of the beams 18, ~o.
When a very low load range is celected, the transducer 10 caI) be used as an inclinometer. In this configuration, t}e contact points 5~, 52 are removed, and the access hcles to the mass 14 are capped off. In the inclinometer mode, the weight of mass 14 provides sufficient force '.o displace itself against the springmembers 18, 20 of linkage 16. The closer the displacement axic is to vertical, the greater the displacement. T}us, the amount of displacement of mass 14 provides an ir.dication of the angle of inclination of the transduce~ 10. The angle of inclination ~ of WO93/18380 PCT/US93~017~5 i93 the axis of disp~cement from vertical may be calculated by cos~'[ mg]
kx where m = mass of mass 14, . g = acce~eration due to gravity, k = sprir:g constant of the linkage 16, and x = displacement of mass 14.
A similar device can serve as an aecelerometer for accelerations in the z direction.
While this ~.nvention has been particularly shown and described wilh references to preferred embodiments thereof, it will ~e understood by those skilled in the art that various changes in form and details may be made therein without department from the spirit and scope of the invention as defined by the appended claims.
For example~. the first mass need not completely enclose the secord mass. The first mass ~ay simply wrap around the ~econd mass in any direction. Also, the second mass r;ay be located above or below or next to the first mas~. Regarding the beam configuration, the fold-back may comprise more than a single fold.
What is cla~med is:
Claims (20)
1. A displacement measuring apparatus comprising:
a first mass of material;
a second mass of material linked to the first mass of material via parallel beams for allowing displacement between the masses in a direction transverse to the beams and providing return force against said displacement, each of said beams comprising arms displaced relative to each other in the direction transverse to the beams and joined end-to-end; and a sensor for sensing the displacement of the second mass relative to the first mass.
a first mass of material;
a second mass of material linked to the first mass of material via parallel beams for allowing displacement between the masses in a direction transverse to the beams and providing return force against said displacement, each of said beams comprising arms displaced relative to each other in the direction transverse to the beams and joined end-to-end; and a sensor for sensing the displacement of the second mass relative to the first mass.
2. A displacement measuring apparatus comprising:
a first mass of material;
a second mass of material enclosed by the first mass and linked to the first mass of material via parallel beams, said parallel beams allowing displacement between the masses in a direction transverse to the beams and providing return force against said displacement; and a sensor for sensing the displacement of the second mass relative to the first mass.
a first mass of material;
a second mass of material enclosed by the first mass and linked to the first mass of material via parallel beams, said parallel beams allowing displacement between the masses in a direction transverse to the beams and providing return force against said displacement; and a sensor for sensing the displacement of the second mass relative to the first mass.
3. The apparatus of Claim 3 wherein each beam comprises arms displaced relative to each other in the direction transverse to the beams and joined end-to-end.
4. The apparatus of Claim 2 wherein the displacement measurement provides an indication of the force applied to the second mass in the direction of displacement.
5. The apparatus of Claim 2 wherein the displacement measurement provides an indication of the angle of inclination of the apparatus.
6. The apparatus of Claim 2 wherein the first mass, the second mass, and the parallel beams are a single unit formed from a single piece of material.
7. The apparatus of Claim 6 wherein the unit is formed by wire electrical-discharge machining (EDM) techniques.
8. The apparatus of Claim 2 wherein the sensor comprises a Hall effect sensor located within a magnetic field.
9. The apparatus of Claim 8 wherein the magnetic field is formed by two magnets fixedly attached to the second mass, said magnets separated from each other by a fixed gap, and the Hall effect sensor is fixedly attached to the first mass and positioned between the magnets, such that the Hall effect sensor senses the displacement of the masses relative to each other and causes to be generated a signal indicative of the amount of said displacement.
10. The apparatus of Claim 9 wherein the Hall effect sensor is located on a circuit board, said circuit board being fixedly attached to the first mass and passing through the gap between the magnets.
11. A method of measuring displacement comprising:
providing a first mass of material and a second mass of material;
linking the two masses via parallel beams to allow displacement between the masses in a direction transverse to the beams and provide return force against said displacement, each of said beams comprising arms displaced relative to each other ?n the direction transverse to the beams and joined end-to-end; and sensing the displacement of the second mass relative to the first mass.
providing a first mass of material and a second mass of material;
linking the two masses via parallel beams to allow displacement between the masses in a direction transverse to the beams and provide return force against said displacement, each of said beams comprising arms displaced relative to each other ?n the direction transverse to the beams and joined end-to-end; and sensing the displacement of the second mass relative to the first mass.
12. A method of measuring displacement comprising:
providing a first mass of material and a second mass of material;
enclosing the second mass within the first mass;
linking the two masses via parallel beams, said parallel beams allowing displacement between the masses in a direction transverse to the beams and providing return force against said displacement, and sensing the displacement of the second mass relative to the first mass.
providing a first mass of material and a second mass of material;
enclosing the second mass within the first mass;
linking the two masses via parallel beams, said parallel beams allowing displacement between the masses in a direction transverse to the beams and providing return force against said displacement, and sensing the displacement of the second mass relative to the first mass.
13. The method of Claim 12 wherein each beam comprises arms displaced relative to each other in the direction transverse to the beams and joined end-to-end.
14. The method of Claim 12 wherein sensing step provides an indication of the force applied to the second mass in the direction of displacement.
15. The method of Claim 12 wherein the sensing step provides an indication of the angle of inclination of the apparatus.
16. The method of Claim 12 wherein the providing and linking of the two masses comprise forming the two masses and the parallel beams from a single piece of material.
17. The method of Claim 16 wherein the forming is accomplished via wire electrical-discharge machining (EDM) techniques.
18. The method of Claim 12 wherein the sensing is provided by a sensor comprising a Hall effect sensor located within a magnetic field.
19. The method of Claim 18 wherein the magnetic field is formed by two magnets fixedly attached to the second mass, said magnets separated from each other by a fixed gap, and the Hall effect sensor is fixedly attached to the first mass and positioned within said gap, such that the Hall effect sensor senses the displacement of the masses relative to each other and causes to be generated a signal indicative of the amount of said displacement.
20. The method of Claim 19 wherein the Hall effect sensor is located on a circuit board, said circuit board being fixedly attached to the first mass and passing through the gap between the magnets.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US844,126 | 1992-03-02 | ||
| US07/844,126 US5339699A (en) | 1992-03-02 | 1992-03-02 | Displacement/force transducers utilizing hall effect sensors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2130193A1 true CA2130193A1 (en) | 1993-09-16 |
Family
ID=25291890
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002130193A Abandoned CA2130193A1 (en) | 1992-03-02 | 1993-02-26 | Displacement/force transducers utilizing hall effect sensors |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5339699A (en) |
| EP (1) | EP0629285B1 (en) |
| JP (1) | JPH07504507A (en) |
| AT (1) | ATE151874T1 (en) |
| CA (1) | CA2130193A1 (en) |
| DE (1) | DE69309913T2 (en) |
| WO (1) | WO1993018380A1 (en) |
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-
1992
- 1992-03-02 US US07/844,126 patent/US5339699A/en not_active Expired - Lifetime
-
1993
- 1993-02-26 JP JP5515783A patent/JPH07504507A/en active Pending
- 1993-02-26 AT AT93906251T patent/ATE151874T1/en not_active IP Right Cessation
- 1993-02-26 DE DE69309913T patent/DE69309913T2/en not_active Expired - Fee Related
- 1993-02-26 EP EP93906251A patent/EP0629285B1/en not_active Expired - Lifetime
- 1993-02-26 WO PCT/US1993/001755 patent/WO1993018380A1/en active IP Right Grant
- 1993-02-26 CA CA002130193A patent/CA2130193A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP0629285A1 (en) | 1994-12-21 |
| WO1993018380A1 (en) | 1993-09-16 |
| JPH07504507A (en) | 1995-05-18 |
| DE69309913D1 (en) | 1997-05-22 |
| DE69309913T2 (en) | 1997-10-23 |
| ATE151874T1 (en) | 1997-05-15 |
| EP0629285B1 (en) | 1997-04-16 |
| US5339699A (en) | 1994-08-23 |
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| FZDE | Discontinued |