RU1770732C - Displacement-to-code transducer - Google Patents

Abstract

The invention relates to measuring technique and improves the accuracy of measuring displacements, gaps, and the like. The converter contains a capacitive sensor, a switch, a measuring oscillator, a frequency converter, a stabilized oscillator, a frequency meter, an automatic frequency block, two keys, a memory element, a reference element, a digital frequency ratio meter, a reference register, a digital switch, a memory register, a digital-to-analog converter tunable generator and control unit. 1 ill.

Description

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WITH

The invention relates to measuring technique and can be used to measure displacements, clearances, and the like.

Known converters displacement capacitive type. One of them is a converter of small increments of capacitance or inductance, containing exemplary and controlled elements connected via a key to a measuring generator, a mixer, a local oscillator, a low-frequency amplifier, and a frequency-locked loop (AFC). A disadvantage of the known converter is the low accuracy of the conversion, due to the fact that not all elements of the circuit are covered by the P AFC circuit and their influence is not taken into account.

Capacitive displacement transducers are known in which a test method for improving accuracy is implemented. A disadvantage of the displacement transducers in which the test method is implemented is the greater complexity due to the need to perform a special test displacement. The elimination of the multiplicative component of the error is carried out using a leverage system. In addition to complexity, the lever system introduces an additional error due to backlash in the joints, which can negate the gain in accuracy when applying the test method.

The prototype is a displacement measuring device comprising a capacitive sensor connected in series, a first key, a self-oscillating measuring device, a frequency converter, a frequency meter, an automatic frequency control unit, a second key, a memory element, a reference generator and a switching voltage generator.

A disadvantage of the known device is the lack of accuracy.

V4

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About CO N3

due to the fact that the multiplicative component of the systematic error is not excluded from the measurement result.

An object of the present invention is to improve the accuracy of a converter.

This goal is achieved by the fact that the displacement transducer into a code containing a capacitive sensor connected to the first input of the switch, the output of which is included in the frequency-dependent circuit of the measuring oscillator, connected by its output to the input of the frequency converter, to the other input of which a stabilized oscillator is connected, the output of the frequency converter is connected with the input of the frequency meter, the outputs of the measuring and stabilized oscillators are also connected to the corresponding inputs of the auto block frequency adjustment, the output of which through the first key and the memory element is connected in series to the frequency adjustment circuit of the measuring oscillator, the control inputs of the switch of the first key and the frequency meter are connected to the corresponding outputs of the control unit, a model element connected to the second input of the switch, a tunable generator are introduced , a digital frequency ratio meter, a reference register, a digital comparator, a memory register, a second key and a digital-to-analog converter, moreover, The frequency converter and the tunable generator are connected to the inputs of the digital frequency ratio meter, the output of which is connected to the first input of the digital comparator connected to the second input with the reference register, the output of the digital comparator via the second key in series, the memory register and the digital-to-analog converter are included in the frequency adjustment circuit tunable generator, the output of which is also connected to the corresponding input of the frequency meter, and the control input of the second key is connected to the unit control.

Improving accuracy is achieved by eliminating the multiplicative component of the systematic error (sensitivity error), and eliminating the sensitivity error by introducing new elements: an exemplary element, tunable in the frequency of the generator, a digital frequency ratio meter, reference register, digital comparator, memory register, DAC and related bonds.

The introduction of an exemplary displacement element and the above-mentioned new elements and links allows the formation of a high-frequency signal whose frequency

proportional to the known model displacement, then generate a signal proportional to the unknown displacement, and then generate a code of the ratio of these frequencies, from which it is easy

The value of unknown displacement is found. the value of the model displacement is known, and the obtained code value is free of the multiplicative component of the systematic error.

The drawing shows a structural

motion to code converter circuit.

The converter contains capacitive

a sensor 1 and an exemplary element 2 connected through a switch 3 to a frequency-dependent circuit of a measuring oscillator 4, the output of which, as well as the output of a stabilized generator 5, are connected to the corresponding inputs of the converter

frequency 6 and the frequency adjustment unit 7, connected by its output via a serially connected control key 8 and a memory element 9 to the frequency adjustment input of the measuring oscillator 4, the output of the frequency converter 6 is connected to the input of the digital meter 10 of the frequency ratio, to the other input of which the tunable output is connected generator 11, the output of the digital frequency ratio meter 10 is connected to the input of the digital comparator 12, the other input of which is connected to the reference register 13, and the output of the digital comparator 12 through the serially connected second switch 14, a register memory 15 and a digital to analog converter 16 is connected to input tuning tunable frequency generator 11, the outputs of the frequency converter 6 and tunable

the generator 11 is connected to the corresponding inputs of the frequency meter 17, the control input of which, 8 also the control inputs of the comparator 3 and the controlled keys 8 and 14 are connected to the corresponding outputs of the control unit 18, the functions of which can be performed by a standard programmer or controller, for example, K1- twenty.

The device operates as follows.

To exclude the additive and multiplicative components of the error, a 3-fold operation mode is organized. In the first cycle, the capacitive sensor 1 and

the exemplary element 2 by the switch 3, controlled by the block 18, is disconnected from the measuring oscillator 4, but the first key is closed 6. In this case, the control voltage generated in the automatic frequency control unit 7, through the closed key 8, enters the memory element 9, where it is stored and acts on the reactive element of the measuring oscillator 4, setting its frequency equal to the frequency of the stabilized generator 6, the frequency of which is chosen equal to the frequency of the measuring oscillator 4 with the sensor turned off, providing thereby linearity of the transformation.

In the second clock, the reference element 2 is connected by the switch 3 to the measuring oscillator 4 and the second key 14 is closed. In this clock, the frequency of the tunable generator 11 is tuned to the different difference frequency obtained in the converter 6 and multiplied by some constant coefficient P, for example, equal to 100. This multiplication is carried out using a digital comparator 12, a reference register 13, a memory register 15, a second key 14 and a digital-to-analog converter 16. The adjustment is carried out in this way. In the reference register, the multiplication coefficient P is stored, as already mentioned, equal to, for example, 100. If the number received in the frequency ratio meter is not equal to P, then the digital comparator 12 generates a digital error code, which is transmitted through the key 14 to the memory register 15 and is stored here . This code is converted in the DAC 15 to a control voltage, which is supplied to the frequency control circuit of the oscillator 11, adjusting its frequency to a difference frequency multiplied by a constant coefficient. At the moment of equal frequencies, the key 14 is opened, and the control action is stored in the memory register 15.

In the third step, the reference element 2 is turned off: and the capacitive sensor 1 is connected by the switch 3 to the oscillator 4, the frequency of which, together with the frequency of the generator 5, enters the frequency converter 6, where a difference frequency is formed using a mixer and a low-pass filter, the period of which is proportional measurable displacement. The difference frequency from the converter 6 enters the frequency meter 17, which also receives the frequency of the generator 11, and which operates in the mode of measuring the ratio of the frequency of the generator 11 to the difference frequency of the converter 6.

As mentioned above, the period of the resonant frequency is proportional to the displacement

Tr - K -X, (1)

where K is the proportionality coefficient determining the sensitivity of the transducer;

X is the movement.

At the same time, with the connected model element

1

Tr.obr. K-Hobr. -r, (2)

where P is the frequency multiplier; X0br. - exemplary displacement. The frequency ratio is

p - F ° 6p Tg, P X, „,.

Q -. - (3)

about r.Bob

As can be seen from (3), the result is independent of the coefficient K, which determines the sensitivity, i.e. the multiplicative component of the error is excluded from the systematic error.

From (3) it follows

Y Q Y

LR-Lobre

where Q is the frequency meter reading;

P is the multiplication factor known;

Hobr. - value of model displacement,

The use of the claimed technical solution makes it possible to exclude the influence of the multiplicative component of the systematic error (sensitivity error) on the measurement results and thereby increase the accuracy of displacement measurement.

Claims (1)

The claims A displacement encoder in the code containing a capacitive sensor connected to the first input of the switch, the output of which is connected to the frequency-dependent circuit of the measuring oscillator, connected by its output to the input of the frequency converter, to the other input of which a stabilized oscillator is connected, the output of the frequency converter is connected to the input of the frequency meter, the outputs of the measuring and stabilized oscillators are also connected to the corresponding inputs of the automatic frequency control unit, the output of which through sequentially connected the first key and the memory element is included in the frequency control circuit of the measuring oscillator, the control inputs of the switch and the first key are connected to the corresponding outputs of the unit: control, characterized in that, in order to improve accuracy, it is equipped with an exemplary element connected to the second switch input, digital frequency ratio meter, reference register, digital comparator, connected in series with a second key, memory register, digital-to-analog converter m and a tunable generator, the outputs of the frequency converter and the tunable generator are connected to the inputs of a digital frequency ratio meter, the output of which is connected to the first input of the digital comparator, the second input of which is connected to the output of the reference register, the output of the digital comparator is connected to the input of the second key, the control input of which is connected to the second output of the control unit, the output of the tunable generator is connected to the second input of the frequency meter, the third input of which is connected with the corresponding output of the control unit.