RU1775036C - Differential capacitive displacement meter - Google Patents

Abstract

The invention relates to measuring technique and is intended to expand the measuring range of a capacitive linear displacement meter that contains sectioned potential and shielding electrodes, as well as a current electrode made in the form of a single plate. The sections of the shielding electrode are mounted movably relative to the current and potential electrodes rigidly interconnected and are connected to the bus of zero potential. As it moves, the overlap area of the respective sections of the potential and current electrodes changes. Information on the magnitude of the linear displacement is obtained as the number of pulses taken from the output of the signal processing unit connected to the current electrode through an amplifier and a switch. 3 ill.

Description

cl

with

The invention relates to measuring technique and can be used in all areas of the national economy.

Known capacitive displacement meter 1.

Its high structural complexity and small measuring range limit its scope.

The closest effect in terms of technical essence and 1 is a differential capacitive displacement meter containing two sectioned electrodes mounted in parallel planes with the possibility of relative movement in the direction of changing the area of their mutual overlap and having the same width of sections, the distances between which at the first electrode are equal half the width of one section, and at the second electrode equal to their width, designed to connect the electrodes to the electrodes current and signal processing unit 2.

Its disadvantage is the technological complexity of manufacturing the first electrode with large geometric dimensions, i.e. if necessary, measure large displacements.

The purpose of the invention is to increase the measurement range.

The goal is achieved in that a differential capacitive displacement meter containing two sectioned electrodes mounted in parallel planes with the possibility of relative movement in the direction of changing the area of their mutual overlap and having the same width of the sections, the distances between which the first electrode is equal to half the width of one section, and at the second electrode they are equal in width, designed to be connected to electro

Vj

word about

with a

CA

I will give an AC power source and a signal processing unit is additionally equipped with a third electrode made in the form of a solid conductive plate rigidly connected to the first electrode, three switches, a frequency divider, an amplifier and an inverter, an amplifier and a first switch connected in series with it are connected between the third electrode and the first input of the signal processing unit, to the second input of which the first output of the supply generator is connected, the frequency divider is connected by the input to the same output pi a generator, and the output to the control inputs of the three switches, the second switch is connected directly to the second output of the supply generator by its input, and the third switch is connected through the inverter to the outputs of these switches, and the outputs of these switches are connected to the corresponding sections of the first electrode, which are interconnected with an interval of three sections and form four groups of sections, and sections of the second electrode are connected in parallel and connected to the bus of zero potential.

In FIG. 1 is a block diagram of a differential capacitive displacement meter; in fig. 2,3 - voltage diagrams at points of the block diagram indicated in fig. 1 as a function of time t and magnitude of displacement.

The differential capacitive displacement meter contains three electrodes mounted in parallel planes. The first - 1 and the second - 11 - sectioned electrodes, the third - 2, made in the form of a solid conductive plate, rigidly connected to the first electrode.

An amplifier 6 and a serial switch 5 connected in series are connected between the third electrode and the two first inputs of the signal processing unit 8. The first output of the supply generator 3 is connected to the two second inputs of the signal processing unit, to which a frequency divider 7 connected in parallel is connected inputs of the three switches. The second switch 4 is connected by its input directly to the second output of the supply generator. The input of the third switch 10 is connected to it through the inverter 9. The outputs of the second switch are connected to the two extreme sections in the group of the first electrode 12 and 13. The outputs of the third switch are connected to the two middle sections in the group of the first electrode 14 and 15. Sections the first electrode is interconnected at intervals of three sections 12 with 16; 14c 17;

15 s 18 and 13 s 19, forming four groups of sections, while all sections are spaced at half the width of the section. The second electrode, consisting of parallel-connected sections,

spaced from each other at a distance equal to the width of the section connected to the bus zero potential 20. The minimum number of sections of the first electrode

0 is four, and the minimum number of sections of the second electrode is three. In angle sensors, the length of all three electrodes is the same. In linear - the length of the shielding electrode significantly exceeds

5 shows the length of two other electrodes and determines a predetermined range of displacements. The signal processing unit comprises phase-sensitive demodulators 21 and 22, which form two signal transmission channels. Output

0 of the first one is connected to the input of the pulse forming unit 23, and the output of the second is connected to the input of the pulse forming unit 24. The outputs of these blocks are connected to the input of the block for determining the direction of movement 5 of 25.

Differential capacitive displacement meter works as follows. From the first output of the supply generator 3, a triangular signal U26

0 goes to the input of the second switch 4, the same signal through the inverter 9 goes to the input of the third switch 10 (plot U27, Fig. 2). From the second output of the supply generator 3, the rectangular signal 5 is transmitted to both channels of the computing unit 8 and the frequency divider 7 (IJ28). Thus, the generator simultaneously generates synchronized signals of triangular and rectangular shapes. Divider

0 of frequency 7 divides the frequency of the signal of generator 3 by an even number of times 2m, where m is an integer. In the diagram of FIG. Figure 2 shows the signal U29 for the simplest case, dividing by 2 (t 1), which determines

5, the state of all three switches 4, 5, and 10. During the time 0 - ti, the output of the second switch 4 will be connected to section 12 of the first electrode 1. At the same time, the output of the third switch 10 will be connected to section 15 of the first electrode.

Since the triangles U26 and U27 have the same amplitude and antiphase signals, the currents in both sections 12 and 15 are dependent on the capacitance of these sections relative to the plate of the third electrode 2. Over time, to the output of the second switch 4, section 13 will be connected. A switch 10 will connect section 14. The input circuit of amplifier 6 is made resistive and

low resistance, and therefore, capacitors formed by sections of the first electrode relative to the third electrode act as current generators, and the voltage at the input of amplifier 6 has a shape close to rectangular. The amplitude and polarity of this voltage is determined by the location of the sections of the first electrode 1 relative to the sections of the second electrode 11. For the one shown in FIG. 1 of the specific arrangement of the electrodes over time, the signal at the output of amplifier 6 will be maximum and have a shape corresponding to the RCD diagram. and during the time ti-t2 - minimal - close enough to zero.

When moving the second electrode half the width of the section at the output of amplifier 6, the signal during the O-ti time will be minimum, and during the time - maximum (plot Uai). Using the second switch 5, controlled by the same frequency divider 7, the signal during the time O-ti, is fed to the first channel of the signal processing unit 8 {i.e. phase-sensitive demodulator 21, forming unit 23), and during the time ti-t2 to the second channel of the same unit (phase-sensitive demodulator 22 and forming unit 24). The signals from the output of the phase-sensitive demodulators 21 and 22 (Fig. 3) presented on the diagrams U32 and KZ3. arrive at the inputs of the forming blocks 23. 24. From the output of the forming blocks, signals U34, U35 (Fig. 3), representing the rectangular voltage, shifted relative to each other in space by 90 °, each pulse corresponds to a displacement equal to section width on the sensor. This form is necessary for constructing known transducers for measuring the displacements of an accumulating type of device, which measures displacement by counting the number of pulses generated by the measuring circuit during the movement of the sensor (Domrachev V.G. et al. Circuitry of digital displacement transducers, M. : Energatomizdat, 1987, p. 15-16).

In the simplest case, the direction determination unit 25 consists of an IK trigger, a single vibrator, a reversible counter, and a logic element NOT connected between the trigger K input and the counter input.

The block works as follows. The signal from block 23 (Usi plot) of FIG. 3 arrives at the trigger input of trigger I, the signal from block 24 (Ibs plot) is fed to the reset input of trigger K. When the sensor moves in one direction, the signals from blocks 23 and 24 arrive alternately and the reversible counter calculates the number of pulses received from the block 23.

If the direction of movement changes, the order of arrival of the pulses changes, and if in the first case there was 1 at the output of the logic element and the reversible counter summed the input pulse signal, jo is now at the output

5 of the logic element, the O signal is set and the reverse counter performs a subtraction operation.

Thus, a signal appears unambiguously at the output of the reversible counter

0 determining the amount of movement of the sensing element.

Thus, in this meter, the range of measured displacement is proportional to red, where n is the number of sections

5 on the second electrode, ad is the width of one section, therefore, by choosing the width and number of sections, it is possible to vary the range and accuracy of the device in question over very wide limits.

Claims (1)

Formula of the invention A differential capacitive displacement meter containing two sectioned electrodes mounted in parallel planes with the possibility of 5 relative displacements in the direction of changing the area of their mutual overlap and sections having the same width, the distances between which at the first electrode are equal to half the width of one section, and at the second electrode are equal to their width, as well as an AC power source for connecting to the electrodes and a signal processing unit, characterized in that, for the purpose of 5 to increase the measuring range, it is equipped with a third electrode made in the form of a solid conductive plate rigidly connected to the first electrode, three switches, a frequency divider, 0 by an amplifier and an inverter, an amplifier and a first switch connected in series with it are connected between the third electrode and the first input of the signal processing unit, to the second input of which is connected the first output of the supply generator, the frequency divider is connected to the input of the same output of the supply generator, and the output to control inputs of the three switches, the second switch is connected by its input to the second output of the supply generator directly, and the third switch through the inverter, the outputs of these switches are connected to the corresponding sections of the first electrode, which e & i. interconnected with an interval of three sections and form four groups of sections, and sections of the second electrode are connected in parallel and connected to the bus of zero potential. and 21 about U 27 L 29 oiU 29 and ,  / t FIG. 2 w /// V v U W Fig.z 7, 7,