SU1449845A1 - Multichannel measuring device for differential variable-induction transducer - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure deformations of rotating objects. The purpose of the invention is to simplify the device and expand its functionality by introducing automatic balancing of the measuring channels. Powering the differential inductive sensors 8.1-8.N sawtooth current generated by the DAC 4, and application in measuring transducers based on operational amplifiers (op amps). 11, .1-nN of the current-dividing circuit allows to obtain at the outputs of the OA 11.1-ll.N constant voltages, the magnitude of which is proportional to the difference in inductances of the windings of the respective sensors 8.1.-8.N, and due to this, do not detect which allows to simplify the measuring transducers. Automatic compensation of initial displacements of sensors 8.1-8.N and op-amp 11.1-11.N with a differential amplifier 13, voltage divider 14, DAC 15, ADC 16 and memory block 17 expands the functionality of the device due to the possibility of remote preparation of the device to work. 1 il. i (L

Description

The device contains a pulse about 15 times.

Generation pulses At at 10 counting clock ei; o in on Wednesday 25 8.1-8, switching current. Chip 3 Chip 7 30 The second one is counted according to the formation of the response of the moth, the shape of the Chip stratum is the development of a connection to the status of a zero

Neither 1, Tina 2 control, first counter 3, first digital-to-analog converter (DAC) 4, first switch 5, delay element 6, second counter 7, N inductive converters, each of which is made in the Bl-SW sensor, the first resistors 9o 1-9.N, second resistor 10.1-lOoN and op-amp P. 1-1 UN, as well as the second switch 12, differential amplifier 13, voltage divider 14, second D / A converter 15, analog-to-digital converter (ADC) 16, memory block 17 and recorder 18.

The output of the pulse generator 1 is connected to the input of the first counter 3, the first and second highs of which are connected respectively to the input of the first DAC 4 and the combined inputs of the delay element 6 and the second counter 7, the output of which is connected to the combined address inputs of the first and second switches 5 and 12, block 17 of the memory and the recorder 18. The output of the first D / A converter 4 is connected to the input of the first switch 5, the outputs of which are connected to the middle terminals 8.1-8.N, the outermost terminals of which are connected to the inputs of the operational amplifiers I.1-11.N, non-invented The rotary inputs of which are connected to the common bus through the first resistors 9ol-9.N, and the inverting inputs and outputs are connected through the second resistors 10.1-30.N. The inputs and output of the second switch 12 are connected respectively to the outputs of the operational amplifiers 11; 1-11.N and the first input of the differential amplifier 13, the output of which is connected to the input of the AID 16. The output of the delay element 6 is connected to the control input of the ADC 16, the first and second koto outlets

5 at a time.

five

0

five

The first counter 3 counts the pulses coming from the pulse generator 1 to its counting input. In this case, from the first output of the first 0 counter 3, a linearly increasing digital code enters the input of the first DAC 4 and the first DAC 4 converts ei; o into a sawtooth current supplied to the average output of one of the 5 8.1-8 sensors, N (eg 8.1) through the first . switch 5, which is a current switch. The second output of the second counter 3 pa counts the input of the second counter 7 transfer pulses, 0 The second counter 7 is an address counter that determines the number of the polled sensor, connect the output of the corresponding measuring transducer to the first input of the differential amplifier 13, select the appropriate address in block 17 the memory used to record the digital information on the initial displacement of this sensor, and the registration of the state information of the selected sensor together with its number in the recorder 18, B and The measuring transducers of the other channels, the middle terminals of the sensors 8.2-8.N of which are connected switches 5, the inputs of operational amplifiers 11.2-11.N, are shorted by direct current through the sensors 8.2-8.N, therefore the voltage at the outputs of these operational amplifiers 11.2 -11.N are close to zero.

The sawtooth current entering the midpoint of the selected sensor 8.1 is divided into two parts, flowing through the corresponding windings of the sensor 8.1. If the resistances of the first and second resistors 9.1 and 10.1 are equal and the windings are identical, sensor 8.1 (equality ijx

) The sawtooth voltages at the inputs of the opamp 11.1, caused by the flow of the sawtooth currents through the active resistors 9.1 and 10.1, are equal and attenuated by the opamp 11.1 as common-mode noise. Operational amplifier 11.1 amplifies the voltage difference across the windings of the sensor 8.1, arising from the difference in their inductances.

9845

I where is then Q

the maximum output current of the first DAC 4, corresponding to the digital code at its input All units.

(L + LH) - (L - L) j

uLI LI.

Jli

ALL

iU and

The output voltage is operating and. - - UL7 C LI 1 amplifier 11.1 is equal to

41

15

and

LIVE

I (R (RL + 2) L,

L + dL; L. L - 4L,

25

de L is the inductance of the winding of the sensor in a quiet position;

db is the amount by which the inductances of both sensor windings change during mechanical action (displacement, pressure, etc.);

1, to the currents flowing through the windings of the sensor 8.1. Since the currents have a sawtooth form,

thirty

i, ia then

whether (L. L) i ,, d (Iit) - (L - dL) -j (L + AL) I, - (L - dL) I-z.

When the windings of the sensor 8.1 when constant current flows through them, constant voltages fall, so it has almost no effect on the distribution of the current entering its midpoint, and with equal resistance of the resistors 9.1 and 10.1, the variable components of the currents flowing through the sensor windings 8.1 are equal, i.e.

one

2

15

and

LIVE

I (R (RL + 2) L,

five

0

five

40

45

50

55

where R is the resistance of resistors

9.1 and 10.1;

RI - active resistance of the windings of the sensor 8.1. The value of current I is determined by the reference voltage of the first DAC 4 and is almost unchanged, therefore the output voltage of the measuring converter linearly depends on the change in inductance of the sensor windings 8.1 and the following Ug (; | digitized converter does not require detection).

Before measuring the signals taken from the 8.1-8.N sensors, they measure and memorize their initial displacements, as well as the initial displacements of the operational amplifiers nl-ll.N and the differential amplifier 13. For this, the control bus 2 to the control input of the second The DAC 15 and the second control input of the memory unit 17 transmit a logical zero signal. At the same time, the second D / A converter 15 is zeroed out and zero voltage is applied to the second input of the differential amplifier 13, and the memory block 17 is switched to the recording mode. The voltage from the output of the measuring transducer of the selected sensor 8.1-8.N through the second switch 12 is fed to the first input of the differential amplifier 13, where it is additionally amplified and then fed to the input of the ADC 16, which converts it into digital form, and the conversion starts Controls the input of the A / D converter 16 from the output of the delay element 6. The amount of delay is determined from the expression

t i - t c

+ t

un

+ t Ki-,.

1449845

 Urr

8.1-8.N, read from memory block 17. The second digital converter 15 converts digital information to voltage, and the ratio of the voltage divider 14 is chosen equal to the gain of the differential amplifier 13. In this case, the voltage at the output of the differential amplifier 13 depends only on the change in inductance of the sensor windings 8.1-8. arising due to mechanical stress and does not depend on the initial displacement

ten

where K is the time of pereftpheni first

switch 5; - time to establish the voltage at the output of the measuring transducer; t is the switching time of the second

switch 12;

t, is the time for setting the voltage at the output of the differential amplifier 13. Then the A / D converter 16 starts converting at a time interval equal to t- after the transfer pulse at the second output of the first counter 15 of the measuring transducer for 3 and the beginning of the sawtooth of the current inductance output of the first IIM 4. It should be noted that if 564 PIE11 chips are used as the first counter 3, in which the transfer signal of the 20 renos is a short negative pulse, and as an ADC 16, IC1 1113 chip is used, in which conversion is started by a signal having a short form to memory block 17, a positive pulse yoga, the element, since it is in read mode, must be additionally demanded and o Initial bias invert signal. At the end of the conversion, at the second output, the ADC 16 is generated by it.

pulse Data readiness, according to which in this way, the supply of differential digital information about the initial potential sensors of the selected sensor is written to the memory block 17 at the address that matches the number of the selected 5 sensor 8.1-8.N. At the same time, this information enters the recorder 18, where the health of the sensor is determined.

The address counter 7 sequentially polls all channels and, thus, a digital information about the initial displacements of all sensors 8.1-8 N is recorded in the memory block 17.

In the process of measurement, the control input 2 of the second DAC 15 and the second control input of memory 17 receive a logical unit during the measurement bus 2, the zeroing of the second memory 15 decreases, and the memory 17 is transferred to read mode. At the same time the differential amplifier

sensor 8.1-8.N and the bias of operational amplifier 11.I-11.N, as well as the initial bias of differential amplifier 13. The voltage of the useful signal is converted into digital form by the A / D converter 16 and fed to the recorder 18 together with the number of the polled channel. At the same time, the sensors and amplifiers are maintained throughout the entire measurement process .8 .1-8.N with a sawtooth current and the use of current-dividing circuits in the measuring converters allows to obtain constant voltages at outputs of the operational amplifiers 11.1-11 .N the differences in the inductances of the windings of the sensors S.1-8.N and do without detection, in contrast to the known devices, in which the measuring transducers convert the change in the inductances of the windings of the sensors into an alternating voltage. This simplifies the circuit of the measuring transducer. In addition, the automatic compensation of the initial displacements of the 8.1-8.N sensors and of the operational amplifiers 11.1-11.N extends the functionality of the device due to its remote preparation for operation.

40

50

13 subtracts from the high voltage of the measuring transducer supplied to the first 55 input of the differential amplifier 13 and is the sum of the initial bias voltages and the useful signal, the voltage of the displacement datum formula of the multichannel measuring device for differential inductive sensors containing inductive converters , each of which consists of a differential 8.1-8.N, read from memory block 17. The second digital converter 15 converts digital information to voltage, and the ratio of the voltage divider 14 is chosen equal to the gain of the differential amplifier 13. In this case, the voltage at the output of the differential amplifier 13 depends only on the change in inductance of the sensor windings 8.1-8. arising due to mechanical stress and does not depend on the initial displacement

measuring transducer due to the difference in winding inductances

sensor 8.1-8.N and the bias of operational amplifier 11.I-11.N, as well as the initial bias of differential amplifier 13. The voltage of the useful signal is converted into digital form by the A / D converter 16 and fed to the recorder 18 together with the number of the polled channel. In this case, writing to the memory block 17 does not occur, since it is in the read mode and the information about the initial displacements

These sensors and amplifiers are preserved throughout the process. Thus, the powering of differential inductive sensors 5

8.1-8.N using a sawtooth current and application in measuring converters of a current-dividing circuit allows to obtain at the outputs of operational amplifiers 11.1-11 .N constant voltages proportional to the difference between the inductances of sensor windings S.1-8.N and dispense with in contrast to the known devices, in which the measuring transducers convert the change in inductance of the sensor windings into alternating voltage. This simplifies the circuit of the measuring transducer. In addition, the automatic compensation of the initial displacements of the 8.1-8.N sensors and of the operational amplifiers 11.1-11.N extends the functionality of the device due to its remote preparation for operation.

0

0

Claims (1)

A multichannel measuring device for differential inductive sensors, comprising inductive converters, each consisting of a differential inductive sensor, an operational amplifier and two resistors, as well as a pulse generator, voltage divider and recorder, characterized in that, in order to simplify and expand device functionality, control bus, two counters, two digital-to-analog converters, two switches, delay element, a differential amplifier, an analog-to-digital converter and a memory unit, the input of the first counter, is connected to the output of the pulse generator, and its first and second outputs are connected respectively to the input of the first digital-to-analog converter and the combined inputs of the delay element and the second counter, the output of which is connected to the combined the address inputs of both switches, the memory unit and the recorder, the output of the first digital-to-analog converter through the first switch is connected to the middle terminals of the sensors, to aynie terminals which are connected to vhada 10 4498458 mi operational amplifiers, non-inverting inputs of which through the first resistors are connected to the common bus, and invertirudiyu through the second resistors are connected to the outputs of the operational amplifiers and inputs of the second switch, the output of which is connected to the first input of the differential amplifier, the output of which is connected to the input of the analog-digital converter, the first and the second outputs of which are connected respectively with the combined information inputs of the recorder J5 and the memory block, and the first control input of the memory block, output through a serially connected second digital-to-analog converter and a voltage divider connected to. the second input of the differential amplifier, the control input of the analog-digital converter is connected to the output of the delay element, and the combined second control input of the memory unit and the control input of the second digital-analog converter are connected to the control bus. 20 25