SU1536188A1 - Capacitive meter of distance to earthed surface - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure and control the distance to a grounded electrically conductive surface. The purpose of the invention is to improve accuracy. To do this, a second voltage source 11, a transformer 13 and a capacitor 14 are introduced into the meter, and the capacitive sensor 1 is made in the form of a shielding electrode 2 and a central electrode 3 located in the same plane, which eliminates the influence of the parasitic capacitance. Performing at least one of the sources 4, 11 in the form of a capacitive distance meter to a grounded surface allows one to obtain a result that corresponds to the product or the algebraic sum of two distances. 1 sec. and 2 hp ff, 1 ill.

Description

(21) 4433708 / 24-28

(22) 05.31.88

(46) 01/15/90. Bul № 2

(71) Institute of Electrodynamics, Academy of Sciences of Ukraine

(72) P.I.Boshev. A.V. Krasilenko,

. R.S. Lezhoev.S.V.Makarenko and A.I.Novik

(53) 621.317.39: 531.717 (088.8)

(56) US Patent No. 4386312, cl. G 01 R 27/26, 1976.

US Patent No. 4054833, cl. G 01 R 11/52, 1975.

(54) CAPACITY DISTANCE MEASURING TO GROUNDED SURFACE

(57) The invention relates to a measurement technique and can be used to measure and control the distance to a grounded electrically conductive surface. The purpose of the survey is to increase accuracy. For this purpose, a second voltage source 11, a transformer 13 and a capacitor 14 are introduced into the meter, and the capacitive sensor 1 is made in the form of a shielding electrode 2 and a central electrode 3 located in the same plane, which eliminates the influence of the parasitic capacitance. Performing at least one of the sources 4, 11 in the form of a capacitive distance meter to a grounded surface allows to obtain a result corresponding to the product or the algebraic sum of two distances, 1 sec., 2 з, п, ф-л, 1 Il.

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The invention relates to a measurement technique and can be used to measure and counter the distance to a grounded plectrical conductive surface.

The purpose of the invention is to improve the accuracy of the estimates of the influence of the parasitic capacitance of the sensor,. also the expansion of functional possibilities by measuring the production or algebraic sum of two distances.

The drawing shows the block diagram of the meter.

The meter contains a capacitive sensor 1 with a shielding electrode 2 and a central electrode 3, a voltage source A, a switch 5, a capacitor 6, an amplifier 7, a phase-sensitive detector 8, an integrator 9, a switch 10, a voltage source 11, a pulse generator 12, a transformer 11, a capacitor 14 and a zero potential bus 15.

The voltage source 4 is connected to the first information input of the switch 5, the second input of which is connected to the zero potential bus 15. The output of the switch 5 is connected to the input of the amplifier 7 through the reference capacitor b. The phase-sensitive detector 8 and the integrator 9 connected to the output of the amplifier 7 form an automatic balancing system. The information inputs of the switch 10 are connected respectively to the integrator 9 and voltage source 11. The control inputs of both switches and the phase-sensitive detector 8 are connected to the generator output 12 rectangular pulses. The transformer 13 is made on a ferromagnetic core (for example, on a ferrite ring). Its cores are made with shielded wire, the central core of the wire performs the functions of secondary winding, its beginning is connected to the input of amplifier 7, and its end is connected to the central electrode of sensor 1. The braid of the screened wire performs the functions of the primary winding 15 (at the input of the amplifier 7), and the end is connected to the shielding point 2 of the sensor 1 and through the coupling capacitor 15 to the CURRENT of the second switch 10.

d 5

0

five

The meter works as follows.

The pulses from the generator output of 12 rectangular pulses control the operation of the switches 5 and 10 in such a way that an alternating rectangular voltage is formed at their inputs, the amplitude of the pulses of which is equal to the difference of the constant voltage at the inputs of the switches 5 and 10.

Transformer 13 performs the functions of a repeater, at the same time forming a surface, equipotentially shielding the secondary winding of the transformer. Isolation capacitor 14 prevents the voltage of the transformer core from being saturated with direct current. The automatic balancing system formed by the series-connected amplifier 7, the phase-sensitive detector 8 and the integrator 9 causes the signal at the input of the amplifier 7 to zero. In this case, the voltage drop on the reference capacitor 6 is equal to the voltage at the output of the switch 5, the voltage drop on the capacitive sensor is equal to the secondary voltage of the secondary winding of the transformer 13, and the currents through the reference capacitor 6 and sensor 1 are equal to each other.

Voltage at the output of a capacitive distance meter to a grounded surface

 C -Ј 1 s.

g

0

five

0

five

Where

and - voltages at the outputs of sources of constant voltage 4 and 11, respectively; CQ - model capacity

capacitor 6; Cx is the working capacity of the sensor 1.

The transformer 13 can be made not only with the primary winding combined with the braid of the shielded wire of the secondary winding, but also with a separately made winding. This may be necessary if the transformation ratio needs to be changed, when the number of turns in the primary winding should be different from the number of turns in the secondary winding. Thus, it is possible to widely change the sensitivity of the measuring transducer, gmcc: yy and ei on

,, Ь 1 Го

 :

and

Z

where N, and

N. - the number of beats in the primary and secondary windings of the transformer 13.

When two or more capacitances are connected in series, measuring the distance to a grounded surface, the change in the ratio N ,, / N allows to sum their input signals with different weights.

Consecutive connection of two or more distance gauges along a grounded surface is necessary, for example, in the following cases.

1. Measurement of the thickness of the conductive coating or tolmin light carrier on a conductive, grounded substrate. At the same time, dpa of a distance meter, one

of which measures the distance to the surface of the grounded substrate, and the other to the surface of the tape or coating. The output voltage of the circuit of the two meters is proportional to the distance difference, i.e. Directly to the thickness of the tape or coating, the first distance meter to a grounded surface should be used as the source 11 of the voltage of the second distance meter, and the polarity of the voltage sources of these meters should be different,

2. Measurement of the distance to a grounded surface under conditions of significant changes in the dielectric constant of the medium and temperature deformations of the object and the sensor. The first of two distance meters to a grounded surface is used as voltage source A. The signal at its output contains information about the changing characteristics of the environment and accordingly changes the sensitivity of the rms distance meter to a grounded surface.

Claims (3)

1. Capacitive distance meter to a grounded surface, co0 holding the first exudes; i i, two switches, capacitive sensor, specimen capacitor, PIUHV of zero potential, h remove, phacochungsg-on detector, the voltage of which through the integrator is connected to the first signal input of the first switch, the output of the voltage source nepFtoro is connected to the first signal to the input of the second switch, whose output is connected to the signal through a series-connected exemplary capacitor and amplifier g to the input of the phase-sensitive detector, the output of the pulse generator is connected to the inputs of the control of the Aa-sensitivity sensor, the first switch and the second switch, the second signal input of which is connected to the zero potential bus, so that , with a chain of increasing accuracy, a second voltage source is inserted in it, a separating capacitor and a transformer, and the capacitive sensor is made in the form of central and shielding electrodes located in the same plane, the beginning of the primary winding of the transformer It is connected to the PMKOCTHOIO sensor shielding electrode and through a coupling capacitor to the input of the first switch, the second signal input of which is connected to the input of the second voltage source, zero potential terminals of the transformer primary winding, the secondary winding of which is connected between the central electrode of the capacitive sensor and the amplifier input . 0 five 0 2 Measuring device according to claim 1, 1, oo tl and - chi and u so that, in order to expand the information capabilities by measuring the product or the algebraic sum of two distances, at least one of the voltage sources is capacitive a distance meter to a grounded surface 3. The meter PP. 1 and 2, about t - l and h a and y with the fact that the primary winding of the transformer is made in the form of a braid, and the secondary winding - in the form of the central wire of a shielded cable.