SU769308A1 - Method and device for measuring displacements - Google Patents

Description

correction of the output characteristics of the converter in the entire measurement range when the external conditions change.

The goal is achieved by switching the outputs of the measuring circuits to a parallel-to-counter, measuring the magnitude of the output signal, comparing the received output signals and judging by their difference about the displacement.

The difference between the device that allows a new method to be implemented is that it is equipped with an adjustable switch connected between the outputs of both measurement circuits and the input of the recording unit, and the control unit whose output is connected to the control input of the controlled switch and to another input of the unit registration.

The recording unit can be made in the form of serially connected analog-to-digital converter and a reversible counter.

The drawing shows a schematic diagram of an apparatus for carrying out the method.

The device contains a differential transformer converter / displacement with a pair of stationary windings 2 and 3 and a pair of movable windings 4 and 5 located on both sides of the stationary windings: in the zero position - on the ravi distance from them. One PGFA windings 2 1 3 is included in the measuring circuit 6, made in the form of a bridge on four transistors, to the input diagonal of which is connected via a transformer 7 a source 5 of an AC supply voltage. Another pair of windings 4 and 5 is included in the second measuring circuit 9, performed on two transistors. The load resistors 10 and 11, which form the outputs of both measurement circuits, are connected via a controlled switch 12 to the recording unit 13. The control unit 14 is connected by the output to the control input of the controlled switch 12 and to another input of the registration unit 13, which can be made in the form of serially connected analog-digital converter (ADC) 15 and a reversible counter 16. The output of the device is removed from the output of the sensor.

The method is as follows.

With the power supply of the control unit 14 and the controllable switch 12 connect the output of the measuring circuits 6 and 9 in parallel and are connected to the input of the ADC 15. Since the currents / n, and / n, in the load resistors 10 and // measurement circuits 6 and 9. Can be described in a linear approximation by the expressions

;P

/ i :, fli-v and / and,,

where fli and Q2 are the gains of the gauge, x sche 9 and 6, respectively;

X is the measured displacement, then the analog output signal V, measured at the input of the A / D converter 15 when the outputs of the measuring circuits are connected in parallel, is described by the expression

1 8., - / g, - o .. a., X k., X,

(2)

where, (- input resistance of the ADC;

1 + 2 - total KOEF1 tsent transfer.

The A / D converter converts this signal to a code recorded in reversible counter 16, which is turned ON in direct counting mode by control unit 14.

In the next measurement step using the control unit 14 and the controlled switch 12 of the EOT connection, the outputs of the measuring circuits 6 and 5 are parallel-to-counter EE measurements of the output signal

1/2 equal to

V, /.J/H. - / hj -, - a,. k, - :. (3)

where kz is the differential transmission coefficient.

The signal Vz is converted into ADC 15 into a code. arriving at the reversible counter 16, which is switched by the signal of the block 14 to the reverse mode, so that this signal is subtracted by EEZ of the signal Vi recorded in it.

At the output of counter 16, a signal Avyh is generated; equal

(, -Y2) -X.

(four)

Since when the voltage of the supply source 8 of the ambient temperature changes or due to the aging of the elements, the transfer coefficients ki and k of the Eothers menu are similar (due to the fact that they are functions of the coefficients E1 and a, and az of the Effectiveness circuits, which change with the pressure). due to the fact that in the circuits measuring EOTs CEEs of the same transducer), the error of EE measurement by this method is significantly reduced. If, for example, the transfer coefficients and, and kz will get some

increments L and A / fej (due to the instability of the external conditions), then the output signals Vi and 1/2 in accordance with equation5, (2) Е: (3) will be equal to:

(fei + and (kz + & k2) x,

therefore, the signal of the left will become equal

Hvyh {() + (Afti-Afeojk

that is, the absolute measurement error is reduced by the value of DY2 at any point in the measurement range.

Obviously, these considerations are also valid in the event that the transformation of the converter is described not only by a linear equation, as shown above, but also by a higher degree polynomial.

Fore: Mule Invention

Claims (3)

1. A method for measuring stirring with a transformer converter having a pair of moving and a pair of stationary windings, each of which is included in one of two measuring circuits: the outputs of the measuring circuits are connected in parallel in accordance with and measured by the size of the output signal, about and with the fact that, in order to improve the accuracy of measurements, the outputs of the measuring circuits are switched parallel to the end of the channel, the output signal is measured, the resulting output signals are compared and, judging by their difference, the displacement nii. 2. A device for carrying out the method according to claim 1, comprising a transformer converter of displacements with a pair of moving and a pair of non-moving windings, two measuring circuits with different transmission coefficients, each of which includes a corresponding pair of converter windings, n a recording unit, excluding the fact that it is equipped a control switch connected between the outputs of both measurement circuits and the input of the registration unit, and a control unit whose output is connected to the control input of the controlled switch and to another input of the registration unit. 3. The device according to claim 2, that is, in that the recording unit is made in the form of serially connected aial-digital converter and a reversible counter. Sources of information taken into account in the examination: 1. USSR author's certificate .YO 386233. G 01 B 7/14, 1970. 2. USSR author's certificate in accordance with the application 2455128 / 18-28, G 01 B 700, 1977 (prototype). J