CA1067601A - Induction-type meter for measuring mechanical quantities - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An induction-type meter for measuring mechanical quan-tities, comprising a first converter to convert the measured quan-tity into a displacement and having elements adapted to be moved relative to each other, and a second converter to convert the displacement into an electric signal and including a magnetic cir-cuit with a block of coils, mounted on one of the elements capable of relative movement, and a diamagnetic screen mounted on the other element capable of relative movement of the first converter, said magnetic circuit being embodied as a system comprised of two parallel parts formed by armored cores mounting said coils and arranged to provide ? gap accommodating said diamagnetic screen with profiled working edges. The inclination angle of the screen with the direction of movement may be varied.

Description

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The present invention relates to measuring devices and more particularly to induction-type meters for measuring mechani-cal quantities, which meters find application for measuring force, forque, vibration, acceleration, displacement, and the like.
Induction-type meters for measuring mechanical quanti-ties are used in technology for converting various displacements caused by the quantities to be measured into an electric signal suitable for remote control, the meters comprising a converter to convert the controlled parameter into a displacement, a con-verter to convert the displacement into an electric signal andan electric measuring circuit shaping a specific signal at the output thereof.
Known in the art are various designs of induction-type and transformer converters to convert displacements into electric signals (having variable size of magnetic gap, variable gap area, solenoid-operated, magnetoelastic, and the like), operating at frequencies of up to 1000 Hz.
Said converters for converting displacements into electric signals, as a rule, include a closed-loop magnetic cir-cuit, an exciting coil, measuring coil, and a movable armatureconnected to the object being displaced.
Their common disadvantage resides in the fact that they feature limited sensitivity and accuracy which is due to the readings thereof being dependent on uncontrollable mutual dis-placements of the coils and the armature, which disadvantage entails the use of guides and requires a higher ~0~7~01 degree of sophlstication of che de~i~n. Moreover, they suf~er from the appearance of a reverse e~ect whlch can ~e reduced by decreasing the value of ou-tput signal, w~ich in turn ~ecessitates the us~ of i~volved seco~dary apparatus-es, limits the distance between the displaceme~t converter and the amplif`ier of the electric measuring circuit and restricts the ~ield o~ application for the co~Yerters.
Al~o known i~ the art are inductio~-type converter~, conYerting displacements into electric signals, also compri~-ing a field coil, a mea~uring coil, but with a mag~tic screen, the coils o$ these converters bei~g connected i~to the circuit of high-frequency o~cillatora and cha~gin~ their inductivity in response to the displaceme~t of a me~al plate (screen) ¢o~nected to an element adapted to re~pond to a variation of ~orce, torque, and other controlled para-meter~.
~ aid co~verters, converting di~plac~ments into an electric signal mak~ use of an open-loop, magnetic circuit s~stem, which permit~ the setting o~ several coil8 at various required di~tances relatiYe to each other and the use of variou~ly shaped screens, which features pe~mit to v~r~ the range o~ measurement~ and the slope o~ the static characteristic of the meter~.
Howe~er, tbe above-described con~erter~ also ~a~e th~ir disadv~tages, re~iding in t~e pre~ence of cons~derable effect~ of uncontrolled transverse displaceme~ of the ~cree~ a low degroe of contact between mutually i~ductiv~
coil~ which reduce~ the output ~ignal leYel, and al~o in -- 3 ~

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the mutual effect of coil~ which ara not inducti~el~ coupl-ed to each o-ther.
In the ca~e~ discus~ed above, the magne~ic circuitEi o~
converters conver-ting displacement into ele¢tric 8ignal~
can be embodied in any conven~io~al i3hape, such as, ~-shape, U-shapes cup-~hape, iand the lik~.
~ L~o known in the art i8 an induction-type co~verter for mea uring mechanical qua~tities, including a con~erter to convert tho controlled parameter into a displacemeat, a converter to convert the di~placement into an electriG
signal, wherein the ~irst converter featurea elements adapted to bo moved relative to each other in respon~e to a change in the controlled parameter, which eleme~t~ mount a magnetic circuit with a block of coili3 coupled to the circuit of a ~elf-e~cit~d o~cillator~ and a metial screen o~ the second converter.
An~ change of the controlled parameter, for example,~orce, re~ults in a relative displacement of the coil bloc~
and the scree~, thu~ changing in turn the coefficients o~ mutual inducta~ce of the coils, which lead~ to the appear-ance of a resultant voltage acros~ the output o~ the , differ~ntial electric mea~uri~g circuit ~differential trans-former).
A diiea~vantage wbich i~ common to all conven~ional meters ~or measuriag me¢hanical quantitie~ i~ a rather in-olved design re~ultin~ - ~ requirement to provide spocial devices ~or protectin~ the converter converti~g .. ~ . , . . . ~, .

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the controlled parameter into a displ~ceme~t from lateralcomponents of the load, and ~or protecting ~he converter for con~erting the di~placoments into an ele¢tric 9ignal from tran~erse di~placement~, a~ ~11 a~ stif~ require-ment~ im~os~d on th~ installation of said mechanical quantitie~ meters in the des~gnated plac~.
Another disadvantage oi th~s above-described meters resides in the difficulties experienced in adjusting and matching the working stroke in re~pon~e to a preset conver-sion characteri~tic or when correctiDg same in re~ponse to t~e environme~tal effect, or a temporary change of the c~aracteristic.
It is an obJect of the present i~ventio~ to provide an induction-type meter for measuring mec~anical guantitie~, combining the advantages of a clo~ed-loop ~nd open-loop magnetic circuits in w~ich meter the above-described di~-advantage~ would be avoided.
Particularly, a con~iderable working gap ~ould be provided between t~e coil~ with inducti~e coupling, w~ich gap s~ould ~e ~uf~icientl~ large to pre~ent the ef~e¢t oi uncoatrolled (transver~e) displacement~ of the ~creen on the value o~ the output ~ignal. The field con~iguratio~ of the induction-couplsd coils mu73t be 73uch a3 to ensure the possibilit~ of using ~creens haviD~ a~ required profile - o~ the working edge.

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The magnetic field must encompass only theinduction-coupled coils and there must be no magnetic field in the region of other coils. The magnetic system must permit the induction non-coupled coils to be arranged in the required position and ensure the possibility of their movement as a result of adjustment of the meter, a change of its characteristic of correction of the characteristic in response to changing external factors.
According to the present invention there is provided an induction-type meter for measuring a controlled mechanical : parameter comprising in combination: a first converter means for converting the controlled mechanical parameter into a displacement; said first converter means having elements `~ capable of relative movement; a second converter means for converting said displacement into an electric signal comprising a magnetic circuit with a block of coils and a diamagnetic screeen; said magnetic circuit embodied as a closed-open loop system comprised of two parallel parts formed by armored cores upon which are mounted said coils and arranged to provide a gap; said magnetic circuit being mounted on one of said elements capable of relative movement of said first converter;
and wherein said diamagnetic screen includes profiled working edges and is secured on the other one of said elements capable of relative movement of said first converter and is disposed in said gap; and said meter further including means for varying an inclination angle of said screen with said direction of movement.
In order to adjust the displacement conversion characteristic into an electric signal, said coil block and said diamagnetic screen are preferably embodied with a provision ' :

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for movement relative to each other.
~ l~he adjustment of the characteristic o~ displacement conversion into an electric ~ignal i~ prefsrably achieved by a provision for relative movement o~ said diamagnetic screen an~ said block oi coils.
~ utomatic correction o~ the conversion characteristic in re~ponse to varying exterDal conditio~ i preferably achieved by providing the induction-type meter ~or mea~urlng mechanical quantities with a corrector drive mea~, serving ~or changing the angle between the working edge of the diamag~etic screen and the direction of di~-placeme~t thereof.
~ he induction-type meter for measuri~g mechanical quantities according to the present inveDtion ~eatures the following adva~tages over the prior art meters.
1. It permits local shorting o~ the magnetic circuit of the oppositely dispo~ed coils, ~hus permitting the gap between said coils to be increased (at a high signal }evel) and al~o reduce the level and effect o~ random scree~ dis-placeme~ts in the workin4 gap, which i~ achieved b~ u~ing speciall~ shaped cores.

2. ~he open-loop mag~etic ~stem of adjaeent coils permits the coils to be dispo~ed at a~y distance from each other, thus ¢hangi~g the range oi measurement~ whereas the shape oi the magnetic field created by the armored cores permits the slope of the co~verter characteristic to be changed or to ~eate a characteristic having any desired ~ , . . .

1067~;01 shape by cha~ging the aDgle of slope of the screen eoges elative to the axis of its diæplacement~

3. The ~act tha~ the shield and the coils are mou~ted on constructional eleme ts that are capable of relative movement and that the edges of the screen are pro~iled simplifies the adjustment o~ the meter, eneuri~g a preæet co~erter characteri~tic and/or the ad~u~tmen~ thereof in response to a temporary change o~ the characteristic.

4. It provides the possibilit~ o~ carrying out automatic correctio~ depending o~ the changing external co~ditionR, with the help o~ a corrector driYe mea~s.
~ e meter according to the present i~ve~tion permitæ
the level of the output signal to ~e i~crsased 5 to 10 t~meæ with æimultaneous similar reductio~ of power demand as compared with the prior art induction, ~errodynamic and other meter~.
The meter according to the pre~ent inventio~ ~eature~
high a¢curacy which iæ ~ to 3 times better tba~ that o~ a meter ha~ing an open-loop magnetic circuit, whereas the time required for its adjustment under æervic~ conditionæ
i8 substantiall~ leæ~ (by a factor of 3 to 5) as comp~red with other type~ o~ meteræ. In addition to that, the quality requireme~ts for the manufacture of the presant metere ~or measuri~g mechanical quantitieæ are co~siderably less stri~geDt.

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~0~j7601 On the whole, the present invention permits a substan-tial improvement of meterologic characteristics with simul-taneous reduction of the requirements for setting the present me-ter at the point of installation, and also provides a device of a rather simple construction.
The present invention will now be explained in greater detail with reference being had to the preferred embodiments thereof which are represented by the accompanying drawings, wherein:
Fig. 1 illustrates a general view of an induction-type meter for measuring mechanical quantities, Fig. 2 shows a longitudinal section of the meter in Fig. l;
Fig. 3 illustrates an induction-type meter wherein the coil cores are mounted on movable brackets;
Fig. 4 shows another embodiment of the meter in Fig. 3;
Fig. 5 illustrates an induction-type meter according to the invention with the screen mounted on a movable element;
` Fig. 6 shows another embodiment of the meter in Fig. 5;
; Fig. 7illustrates an induction-type meter with a , corrector drive means, for example, a temperature corrector;
- Fig. 8 shows another embodiment of the corrector ` (pressure corrector);
Fig. 9 illustrates the electrical diagram of an induc-tion-type meter for measuring mechanical quantities.

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~L0f~760:1 An induction-type meter for measuring mechanical quan--- tities, for example, force, comprises a resilient force meter 1, which is a converter effecting conversion of the controlled para-meter into displacement ~Fig. 1), the elements 2 and 3 thereof, which are capable of relative movement by resilient deformation of the force meter 1 mount a profiled diamagnetic screen 4 on the one side, and on the other side - a bracket 5 with a magnetic circuit 6 secured thereto, the magnetic circuit 6 comprising two parallel parts 7 and 8, disposed in such a manner as to form a gap "~" between them and made in the form of armored cores 9, 10, 11 and 12, with induction coils 13, 14, 15 and 16 wound thereon.
The magnetic circuit 6 with the induction coils 13, 14, 15 and 16, together with the screen 4 form a converter to convert displacements into an electric signal, of a transformer type.
Fig. 2 illustrates a longitudinal section of the above !~ described induction-type meter for measuring mechanical quantities, showing the screen 4 with working edgeS17 and 18 profiled accord-ing to the required law, the screen 4 partially overlapping the electromagnetic field of the cores 9, 10, 11 and 12.
In Fig. 3 said armored cores 9, 10, 11 and 12 are mounted on a bracket 19 with a provision for movement along , ~ , ;

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guides 20 ~the arrows indicating the direction of movement of cores 9, 10, 11 and 12 and the bracket 19!. For the purpose of their adjustment, the armored cores 9, 10, 11 and 12 are mounted on articulated brackets 21 and 22. The mitred working edges 17 and 18 of the diamagnetic screen 4 ensure zero setting when adjusting the system.
Fig. 4 illustrates another embodiment of movable armored cores 9, 10, 11 and 12, namely: the brackets 21 and 22, which are supporting said cores, are moved along the bracket 19 by means of screws 23 and 24 having a left-hand and a right-hand thread, respectively, thereby effecting the adjustment of the meter of mechanical quantities. The arrows indicate the direction of move-~ ment of brackets 21 and 22.
- The concrete method for moving the brackets 19, 21 and 22 i5 dependent on the type of the resilient element used for providing the force meter 1, also on specific parts used in the construction of the present induction-type meter.
The working edges 17 and 18 of the screen 4 can be pro-filed according to any preset law.
2Q In Fig. 5, the shield 4 is mounted on the bracket 25 ~ith a provision for movement, thereby facilitating the adjust-ment thereof and permitting the required conversion 1q)6 76~D1 characteristic~ to be obtained. In accordance with ~ig. 5, ~he shield 4 is mounted o~ the bracket 25 o~ pivot 26.
As the shield 4 i8 rotated b~ mea~s of the ad~usting mean~
27, the angle between its working edge 1~, 18 and the direction of mo~eme~t will be chaR4ed, thereby correspond-ingly contracting or expanding its co~version characteristi¢.
The arrow~ indicate the direction of di~placeme~t oi ~creen 4 relative to the pivot 26.
~ tg. 6 illugtrates a~other embodi~e~t of the movable screen 4, comprisi~g two similar part8 (elem~nt~) 4' and 4", articulated together in such a manner that a displac~ment of t~e adjusting mean~ 27, cause~ the working edges 17 and 18 of the screen part~ 4 to aliga with the centre of th~
respective pair of arm~red cores 9, ll, lO, 12.
~ his ensures variation of the conversion cbarac~erist~c slope, but o~ the other hand it might cause the ~ero to shiit.
In order to a~oid 3hi~ting the zero when di~placi~
the shiel~ 4, the bracket l9 hRs to be ~dditionall~ moved along the guide~ 20 until the workin~ edges 17 and 18 are alig~ed with the ce~tre of a corresponding pair o~ armored cores 9, ll, lO and 12. Similar eifect can be obtained b~
u~ing a combination wherein the construction includes a rotata~le screen 4 ~ig9 5 and 6) and rotatable cor~s 9, lO, ll and 12 (Figs 3 and 4).
Fig. 7 illustrates a diamagnetic screen 4 secured o~
tbe pivot 26 in the bracket ?5, t~e scree~ being coupled with ; 12 -.

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:1067601 a drive means 28 of a corrector (not shown in the Fig.) The specific design of the drive means 28 is detcrmined by the corrected parameter selected.
For example, to effect temperature correction use is made of a bimetal thermal spiral 28 (drive means), one end thereof being connected to the screen 4 and the other end, to the bracket 25. ~lith the parameters of the bimetal thermal spiral 28 having been properly selected, the present device will ensure automatic compensation of the temperature effect on the conversion characteristic of the induction-type meter.
Fig. 8 illustrates another embodiment of the corrector - drive means for pressure correction. In this case a chamber 29 is provided in the kinematic link defined by the bracket 25 and screen 4, the chamber 29 being separated by a spring-loaded dia-phragm 30, connected by means of rods 31 with the screen 4, the chamber 29 communicating with the pressure source "p" by means of an inlet branch pipe 32.
The electric diagram of the induction-type meter for ~easuring mechanical quantities is shown in Fig. 9.
The diagram comprises a resistor 33 and a Zener diode 34 of the first stabilization stage, resistor 35 and Zener diode 36 of the second stabilization stage, as well as a capacitor 37 which serves as a filter for the alternating voltage of the self-exciting oscillator, (in principle, any known stabilization cir-cuit can be used, provided it is required to meet the operating conditions of the converter).

0 6 7 6~1 ~l'he sel~-exciting oscillator is built eround a tran~istor 38 an~ comprises resistors 39 and 4Q, serving as a bias circuit, and a resis~or 41 serving ~or current stabiliz~tion of the transistor 38, and a capacitor 42 to ~hunt the alternating current of the re~iætor 41.
The oollector of transistor 38 include~ an inductioa, which induction is formed by th~ excitation coil 13 and 14 of t~e displacemeut Converter, which in combina~io~ with capaci-tor~ 43 and 44 ensures the requ$red conditions for sel~-excitation of the oscillator.
Capacitors 45 and 46 connected to the measuring coil~ -15 a~d 16 ~orm the secondary circuit~ e diodes 47 and 48, co~nected thereto serve ~or recti~ing the alternati~
current.
After recti~i~ation and ~iltration by capacitor~ 49 and 50, Yoltages of equal magnitude and rever~e polarity appear acros~ resistors 51 and 52 (i~ the zero position of the screa~ 4). Thus the potential difrerence between poi~t~
53 and 54 in ~his state of t~e converter is ~ero.
di~erential diagram of connection permits to~i~crease the accurac~ of the induction-type meter, improve~ the sen8i-tivity thereof by a factor o~ 2 a~d en~ures the ab~ence o~
voltage across the output (zere Rignal) in the initial state o~ the induotion-type meter. W~en the proces8 o~ measur~ment realized by the induction-type meter for measuring mechani¢al quaLtitie~ require~ to have a certain level o~ signal ~other : `'' . ~ ~' ' ' ' .,, . ~ ' ' . . ' , i7601 than zero) in the initial state, a 5imple convertion circuit Wit~l CoilB 9 and 11 (Fig. 1) is possible.
~ he induction-type meter ~or mea~uring mechanical quantities operates a~ follows.
Direct curre~t fed across the supply buses causes excitation o~ the sel~-excited oscillator, cau~ing the appearance of ~inusoidal volt~ge acros~ t~e coils 13 a~d 14 ~Fig. 1).
~ his voltage creates in the coils 15 and 16 voltage~
whose amplitude depends on the co~trolled displaceme~t~ of the scree~ 4. In the.example of force measurements now considered, the force meter 1 (~ig. 1) i~ strained under the actio~ of applied load causi~ the screen 4 and the magnetic 3y~t~ o~ cores 9, 10, }1 and 12 to be rel~tively di~placed, thereb~ changi~g the relationship between thR
screa~ed coil areas. This leads to a change in the tra~sfor-mation ratio between coils 13, 15 a~d 14, 16, re~pectively, with the result that the voltages acro~s the coila 15 aGd 16 will be dif~ere~t (unlike the initial "zero" state, whe~
these voltage~ have equal amplitude, the transformation ratio between coils 13, 15 and 14, 16 being equal). ~e voltages derived ~rom the coils 15 and 16 are rectified bsr amplitude detectors 47 and 48, smoothed by filters 49 and 50, thereby creatiDg a potential di~f~rence between points`5~ a~d 54, which i~ proportioaal to ~che voltage difference across coils 15 and 16, taking i~to co~ideration the cig~ o~ t~e difference.

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1~67601 ~ l'hus, owing to theIelative di~placeme~t of the screen 4 and the magnetic system o~ colres 9, 10, 11 and 12 acro~s the output of the lnduction type meter circuit (Fig. 9), there appear~ a signal whlch is proportional to thi~ di~-placement and correspo~d~ to the force applied to thP force meter 1 (~ig. 1) in the ex~mple consi ~ ed, and havin~ a ~ign uhic~ take into account the dir~ction of this displacement.

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Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An induction-type meter for measuring a controlled mechanical parameter comprising in combination:
a first converter means for converting the controlled mechanical parameter into a displacement; said first converter means having elements capble of relative movement;
a second converter means for converting said displacement into an electric signal and comprising a magnetic circuit with a block of coils and a diamagnetic screen;
said magnetic circuit embodied as a closed-open loop system comprised of two parallel parts formed by armored cores upon which are mounted said coils and arranged to provide a gap; said magnetic circuit being mounted on one of said elements capable of relative movement of said first converter;
and wherein said diamagnetic screen includes profiled working edges and is secured on the other one of said elements capable of relative movement of said first converter and is disposed in said gap; and said meter further including means for varying an inclination angle of said screen with said direction of movement.

2. An induction-type meter for measuring mechanical quantities as claimed in claim 1, wherein said screen is made up of two similar parts articulated together in such a manner that a displacement of said adjusting means results in said working edges of said parts of said screen coinciding with the center of the corresponding pair of said armored cores.

3. An induction-type meter for measuring mechanical quantities as claimed in claim 2, wherein said coils are mounted on brackets movable along guides to enable the working edges of the diamagnetic screen to be aligned with the armored cores.

4. An induction-type meter for measuring mechanical quantities as claimed in claim 1, wherein said means for varying an inclination angle of said screen with said direction of movement comprises a thermobimetal spiral having one end connected to said screen and the other end connected to a bracket which mounts said screen.