SU1337671A1 - Electromagnetic scales - Google Patents

Abstract

This invention relates to electromagnetic load balancing scales. The purpose of the invention is to improve accuracy. The reference coil 10 of a given mass is located on the edge of the gap of the magnetic system, where the edges of the pole tip and the magnetic circuit are made beveled. Under the action of a given constant weight P, the coil 10 is shifted down and the signal from the photodetector 12 is amplified and converted by the amplifier 20 into a direct current 1o which passes through the coil 10, creating an electromagnetic force. The position of the reference coil 10 at the edge of the gap allows you to fully use the working gap for balancing the measured force. The constant current 1 in the reference coil 10 causes its constant heating, which makes it possible to increase the heating, and with it the amp-turns of the coil and to balance a sufficiently large value of the reference weight. 3 il. (L / (jO GS with: gtue.Z

Description

 133767

The invention relates to weighing technology, in particular, to a case with electromagnetic load compensation.

The purpose of the invention is to improve the accuracy.

Figure 1 shows a diagram of the design of electromagnetic scales; on

figure 2 - electrical circuit diagram

which part; Fig. 3 is a graphical induction in the region of the reference coil.

Electromagnetic scales contain a sensing element I with a load-carrying cup 2 for a measured load 3 with a mass rp, an elastic suspension 4 for a sensing element 1, a sensor for moving a sensing element, for example a capacitive sensor formed by plates 5, one of which is placed on the sensing element measuring coil 6 power compensation, located in the working gap of the magnetic system. The magnetic system contains a permanent magnet 7 with a pole tip 8 and a magnetic conductor 9. At the edge of the gap between the tip 8 and the magnetic core 9 there is a reference coil 10 carrying a slot screen 1 I, on one side of which a photodetector 12 is mounted, on the other side an illuminator 13 forming the photosensor of movement of the reference coil 10. The coil 10 is fixed, for example, by means of three radially stretched extensions 14. The measuring coil 6 is connected by means of guide posts 15 located in the slots 16 of the magnetic circuit 9 1. The plate 5 is electrically connected to the input of the displacement sensor 17, the output of which is connected to the voltage converter 18 dU in the time interval controlling the modulator 19. The photodetector 12 is connected to the amplifier 20 of the displacement sensor of the reference coil, the current output of which is connected to to the input of the modulator 19. The output of the latter is connected to the measuring coil 6. A reference coil 10 is connected in series with the current amplifier 20. A sample device 21 is connected to the output of the converter 18.

Electromagnetic scales work as follows.

The standard coil is 10 given mass m, i.e. weight P i in. are located

0

5 Q

five

0

five

I2

on the edge of the magnetic system gap, where the edges of the pole tip 8 and the magnetic core 9 are made bevelled, which ensures a constant gradient of magnetic induction dB / dx const in the region of the gap, and the height h Id is the height of the reference coil (FIG. 3). Under the action of a given constant weight P, the coil 10 is shifted down and the signal dU from the photoreceiver I2 is amplified and converted by the amplifier 20 into a constant current Ijj, which passes through the coil 10 with the length of turns Pp, creating an electromagnetic force

FBX FC - fx with IO (BCP + F b

where vs is the mean

induction at the edge of the gap;

hj, is the height of the coil; (3 X is the displacement of the coil. Thus, the electromagnetic force FPJ is characterized by the constant component F „1.8. ,,,

Ltd

 1y TCrVr and variable component fx Wp. . dx, where W.PJ ,, sB / h (negative stiffness), depending on the movement of the reference coil, the weight of the reference coil P, the length of the coils 1 and the current 1 are calculated so that the constant component Fj balances the weight P „ i.e. F P „P, 1, K, B ,, and variable f compensated for the force from the stiffness W of the elastic suspension (stretching) when moving by lx, i.e. fj Wpdx. The force f is the force of the negative stiffness, which is created by the corresponding direction of the current 1, while at the same time balancing the weight P ,. This is possible only when the reference coil is located on the outer edge of the gap. When placed on the inner edge of the gap, one direction of current 1 balances the weight P, but creates the effect of positive rigidity, another direction 1 though creates negative rigidity, but the force F coincides with the direction P and does not balance the latter.

In the absence of measurable cargo 3 with a mass t, i.e. R d, the measuring system is loaded with its own weight P - a passive container, which causes an initial displacement

The measuring coil, which leads to a change in the capacitance between the plates 5. The change in capacitance is converted by the sensor 17 into an electrical signal y, "which is amplified, rectified and converted by the transducer 18 into a relative length T (, is .

During the time t in the measuring coil 6 current flows I the average value of the pulse current 1 creates a balancing force

strength

H / T.

about

t bja,

T,

where E, is the length of the coils Since

g -: 0 oksv „

drift zero reference balancing system,

- .Mj.o.Jj.I

F,

fcKJ,

21 counting device

is preliminarily reset to the number, JQ also the component of the error

addition to which is the number of pulses corresponding to the duration of SD.

Thus, in the absence of a load, zero readings are recorded in the reading device 21 at t JJ equal to 0. At 4 g 7 O the reading device records this drift, causing a zero error

When a load 3 with mass m is applied, the sensitive element is displaced downward by a distance lx, which causes a proportional change in the capacitance of the plates 5, which is converted to a voltage dU, by the displacement sensor 17. The voltage of the LC is amplified and transformed by the converter 18 into a change in the relative duration tn / Tg. The average value of the current in the coil

x

 I -i

creates electromagnetic forces p, B I bi JjiP- -lAo.i,

   glou

balancing the strength of the tin of P load,

those.

PX

Thus, the measured carrier P is proportional to the time duration tj, and does not depend on changes in the magnetic induction BQ.

Thus, the reference coil eliminates the influence of the instability of the magnetic induction on the conversion result, as well as the nonlinearity of the conversion caused by the change in the magnetic induction from the demagnetizing effect of the current 1. The location of the reference coil on the outer edge of the gap allows

negative stiffness to almost completely compensate for the mechanical stiffness of the elastic suspension (stretch) and to ensure the static nature of the weight balance

reference coil. Without

the stiffness of the reference coil is in the position of indifferent equilibrium, and the mechanical coil (displaced part) brought to the input and

electric zero drifts do not affect the result of converting a PD to a current 1 ,.

The absence of a drift zero electronic balancing system eliminates

the sensitivity of the balancing measuring system caused by it. The location of the reference coil on the edge of the gap, i.e. in the usually unused area, it makes it possible to effectively, almost completely, use the working gap for balancing the measured force. The constant current Ig in the reference coil causes a constant heating of the coil, which makes it possible to significantly increase it, and with it the ampere-turns of the coil and to balance a sufficiently large value of the reference weight.

formula of invention

Electromagnetic scales, containing; and a weighing pan mounted

on a sensing element having a power compensation coil and a position sensor connected to one electrical equilibration and reference circuit, a reference coil with a given mass mounted on an elastic suspension, and a position coil of a reference coil connected to another equilibrium electrical circuit common to the reference and coil power

Compensation magnetic system formed by a permanent magnet, attached to it by a pole tip, a working gap is formed, in which a power compensation coil is placed, characterized in that, in order to achieve accuracy.

in them, the working gap is located in the lower part of the magnetic system, and the edge of the magnetic circuit and the pole tip at the outer part of the gap are made beveled and a reference coil is located in the formed extended area of the working gap.

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Compiled by V.Shirshov Editor M.Petrova Tehred L.Oleinik

4118/36

Circulation 693 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4

Proofreader L. Pilipenko

Claims (1)

Claim An electromagnetic balance containing a load cup mounted on a sensing element having a power compensation coil and a position sensor connected to one electric balancing and reference circuit, a reference coil with a given mass, mounted on an elastic suspension, and a position coil of the reference coil connected to another electrical balancing scheme common to the reference and power coil I 337671 of compensation, the magnetic system formed by a permanent magnet, a pole attached to it, a working gap is formed in which a power compensation coil is placed, characterized in that, in order to improve accuracy, the working gap is located in the lower part of the magnetic system, and the edges of the magnetic circuit and the pole piece at the outer part of the gap are beveled and a reference coil is located in the formed expanded region of the working gap. fiez