SU1249309A1 - Capacitive meter of angular shifts - Google Patents

Abstract

The invention relates to a measurement technique and allows extending the measurement range of angles of a capacitive angular displacement meter to ± 180 °. The capacitive angle sensor contains two rotatably mounted one relative to the other around a common axis of rotation of rectangular measuring electrodes, one of which is equipped with a grounded guard electrode. These electrodes are placed inside a hollow cylindrical shielding electrode whose axis coincides with the axis of rotation of the rectangular electrodes. The shielding electrode is grounded, and a correction capacitor is connected in parallel with the measuring electrodes, the capacitance of which is selected in accordance with the specified mathematical expression, including the dimensions of the measuring and guard electrodes. When the sensor operates, the parasitic components of the measured capacitance between the active surfaces located at an angle of the rectangular measuring electrodes are compensated, which increases the linearity of the conversion characteristics of the capacitive angle meter in the wide range of measured angles. 1 h. item f-ly, 2 ill. to (l go j; 00

Description

one

The invention relates to measure; 1 technology and can be used for

measure, first change;

The purpose of the invention is to distribute the range of () to measurements of the capacitance of the angle sensor up to 180 °; 1linearize its conversion in this range with the nominal screening electrodes in combination with the correct capacitor of the given capacitance.

FIG. 1 is shown capacitive and; measure of angular displacements, general nid; on f Ig. 2 - capacitive angle sensor, knock), section.

A capacitive angular displacement meter contains a capacitive angle sensor, nr mongular e; 1 spectrods 1 and 2 of which have a common axis 3 (rotation, with which the continuity line of the active internal surfaces of these electrodes or their continuation is combined. The 1st electrode 2 is surrounded by spaced electrodes in the plane of the guard electrode 4. The shielding electrode 5, B1 filled in the form of a hollow cy.chnr, the axis of which is aligned with the axis 3 of the right angles of the right carbon electrodes 1 and 2 capacitive sensor, electrical The cable is connected to a guard electrode 4 connected to the common ground point and, in the point equipotential to it. Straight () angle 1) Pyie electrodes 1- and 2 or at least one of them is shielded outside the meta. A clinical layer, vnolnopnym on the same isolated substrates as nr mogalnye electrodes 1 and 2 of the capacitive sensor. In view of this, between these surfaces of the electrodes there is a decrease in the interconnection of the coupling. ... in the 1 and 2 protodrodnamn,: scheme G, which is designed d, 1I of the control value, back npOHOpHiioHa.iijiioii measurable capacitance C ,; between these electrodes,, with the informative parameter yr,: ia ((between them depending on the corner of the control object (not shown). Between the same electrodes 1 and 2 of the capacitive sensor, the corrective co-detector is 7.

An acoustical angle meter is operated as follows.

When the angular position is changed about 1z, the angle changes (p between the rectangular electrodes 1 and 2 of the capacitive sensor, which leads to a change in capacitance S, between them, the reciprocal of which varies with the circuit 6, This is a parasite bridge circuit. In a capacitive sensor, yi Jia, having the described structure, a cylindrical shielding device, 1 electrode, the value of S. between the electrode, the variation, is determined by the following :

  1 .- -t, L

 - i y.,

(one)

2. (

Have

; 2;

C, + (f

Sf /: # -.

(3)

five

o and b

0 5 o

/

f is the absolute dielectric constant of the medium between the electrodes of the capacitive sensor;

a length parallel to the axis of rotation 3 of the side of the rectangular electrode 2 provided with a guard electrode 4;

the radius of the Euthene surface of the cylindrical shielding electrode;

- distance from the axis of the sides of the rectangular electrode parallel to it, of the rectangular electrode equipped with a guard electrode.

When b R, i.e., at the practical coincidence of the distant side of the rectangular electrode 2, parallel to the axis 3 of the impingement, with the circumference of the inner surface of the shielding cylindrical electrode 5, it becomes equal to

3 rotations to the nearest and respectively.

C, 2pf2 const.

; 41

0 5 o

five -

0

0

With (240.1 /, i.e., with a rather small width of the guard electrode 4 in the area between the axis 3 of the liver and the closest parallel side to it of the rectangular stationary electrode 2 compared to the radius of the inner surface of the shielding electrode 5, component C-) tends to zero in the range of angles ((; 5C.

Therefore, the inclusion of a correction capacitor 7 of a just-capacitance, numerically equal to C |, along the measuring rectangular electrodes 1 and 2 of the capacitive processor, eliminates C from equation (I), which at the output of the capacitance meter of angular displacements get almost linear, unambiguous in the range of the angle q, O - 180 °, the conversion function, which is the capacitance 1 / ws dependence. as a function of angle y. The nonlinearity of the angle transform function in this range does not exceed 0.7%. The high noise-attenuation and compactness of the structure, as well as the stability of the conversion function, make it possible to use a capacitive angle meter also in the range of 180 - 360 °, which does not imply a complication of its design, although the non-linearity of the conversion increases monotonically from 0.7 to 10%.

Claims (2)

Invention Formula . C. Capacitive angular displacement meter containing a capacitive sensor. the angle formed by two flat, pivotally mounted relative to each other by rectangular electrodes, the active surfaces of the electrodes intersect along a straight line coinciding with their axis of rotation, and one of them is surrounded by a guard electrode placed in the common plane and connected to the right angle electrodes a measuring circuit for controlling the magnitude inversely proportional to the capacitance between these electrodes, characterized in that, in order to extend the measurement range, it is equipped with a shielding electr house electrically connected to the guard electrode and designed as a hollow cylinder whose axis is aligned with the axis of rotation of rectangular electrodes, and incorporated between the rectangular electrodes with a correction capacitor. 2. The meter according to claim 1, characterized in that the radius of the inner surface of the cylindrical shielding electrode is equal to the distance from the axis of rotation of the rectangular electrodes to the more distant side of the rectangular electrode surrounded by the guard electrode, and the capacitance C of the correction capacitor is chosen C 2e | - & t2, where e is the absolute dielectric constant of the medium between the electrodes of a capacitive angle sensor; f is the length of the axis of rotation parallel to the axis of the rectangular electrode surrounded by the guard electrode.