SU1529044A1 - Multichannel measuring device for differential inductive transducers - Google Patents

Abstract

The invention relates to instrumentation engineering and can be used to monitor various physical quantities using differential inductive sensors (DND). The purpose of the invention is to increase the speed of a multi-channel measuring device by forcing the DND current and improving the measurement accuracy by eliminating the effect of residual voltages and ensuring identical measuring conditions for all DNDs. The multichannel measuring device contains a pulse generator 1, a delay element 21, a digital-analog converter 3, a counter 4, switches 12, 17, differential inductive sensors 16.1-16.N, a differential amplifier 19, an analog-to-digital converter 20, a recorder 22. By introducing an element 2 delays, integrator 5, inverter 6, adder 7, converters 8, 9, voltage - current, current reflectors 10, 11, switches 13-15, 18, the device provides forcing the sawtooth current through DND 16.1-16.N, which reduces the setting time n direct voltage at the output of differential amplifier 19 and hence improves performance measurement and eliminates the effect of residual stress in the LPS 16.1-16N by their demagnetization, and also measuring their parameters provided one measuring channel, which increases the measurement accuracy. 2 Il.

Description

The invention relates to instrumentation technology and can be used to monitor various physical quantities using differential inductive sensors.

The purpose of the invention is to increase the speed of the device by forcing the current of differential sensors and increasing the accuracy of measurements by eliminating the effect of residual voltages and ensuring identical measurement conditions for all differential inductive sensors.

Fig, 1 shows a schematic of the device; in fig. 2 - timing charts of the device.

The device (FIG. 1) contains a pulse generator 1, a second delay element 2, a digital-to-analog converter 3, a counter 4, an integrator 5, an inverter 6, an adder 7, the first 8, and a second 9 voltage-current converters, the first 10 and the second 11 from - current razryateli, first 12, fourth 13, third 14 and fifth 15 switches differential inductive sensors 16.1-16.N, second 17 and sixth 18 switches, differential amplifier

19, analog-to-digital converter

20, the first delay element 21, the recorder 22.

FIG. 2 denotes the output voltage 23 of the generator 1, the output voltage 24 of the delay element 2, the output current 25 of the DAC 3, the output currents 26 and 27 of the converter 9 and the reflector 10, respectively, the output voltage 28 of the differential amplifier 19,

The first switch 12 is connected by outputs to the first inputs of the respective differential inductive sensors 16.1-16.N. The second switch 17 is connected to the first input of the differential amplifier 19, connected by an output to the signal input of an analog-digital converter 20, connected by an output to the input of the recorder 22, and a control input to the output of the first delay element 21. Counter 4 is connected by outputs to the control inputs of the first switch 12. The output of the pulse generator 1 is connected directly to the first input of the integrator 5, and through the second delay element 2 to the first inputs of the digital-analogue

Q

five

five

0 5 0

d

converter 3, with the input of the first delay element 21 and with the input of the counter 4 connected by outputs to the first inputs of the adder 7 and to the control inputs of the third switch 14 connected by a signal input to the first output of the first current reflector 10 connected by the second output to the signal input of the first switch 12, the input through the first voltage converter 8 is the current with the output of the integrator 5 connected by the second input with the output of the digital-to-analog converter 3, and the output through the serially connected inverter 6 and the second voltage converter 9 - current - with the input of the second current reflector J1 connected by the first and second outputs respectively to the signal inputs of the fourth 13 and fifth J5 switches, the control inputs of which are connected to the outputs of the adder 7 and the control inputs of the second 17 and sixth 18 switches. The signal inputs of the second switch 17 are connected to the corresponding outputs of the first 12 and fourth 13 switches. The signal inputs of the sixth switch 18 are connected to the corresponding outputs of the third 14 and fifth 15 switches and the second inputs of the respective differential inductive sensors 16.1-16.N, and the output is connected to the second input of the differential amplifier 19. The third input of each of the differential inductive sensors 16,1- 16.N is connected to the total width of the device and to the second input of the adder 7 connected by the third input to the input for setting a single signal of the device and to the second inputs of the digital-to-analog converter 3.

The pulse generator 1 is designed to generate pulses, the duration of which is equal to the initial part of the pulse-feeding current of the fast saw (part of the battery, position 26

FIG. 2).

d, the delay Element 2 is designed dp the delay of the pulses from the output of the generator 1 pulses for the time required to zero integrator 5 and equal to the duration of the pulses of the generator 1,

The digital-to-analog converter 3 is designed to convert the held pulses into a two-level current signal (position 25, fig 2)

The counter 4 serves to control the switches 12 and 14 alternately connecting the sensors 16.1-16.N to the drinking and measuring circuits of the device.

The integrator 5 is designed to convert the two-level current from the output of the digital-analog converter 3 to a linearly increasing voltage, the first level of the current of the DAC (all the inputs 1) corresponds to the section AB - fast saw, and the second level of the current (on the first group of inputs - O, and current BC - slow saw 26, fig. 2).

Inverter 6 is designed to invert the voltage from the output of integrator 6.

The adder 7 is designed to increment the control code for the switches 13, 15, 17, and 18 by one compared with the other commutators. The voltage-i current transducers 8 and 9 are designed to convert voltages from the outputs of the integrator 5 and inverter 6 into currents, and these two currents have different directions and coincide in amplitude and shape.

The reflectors 10 and And the current is designed to transfer the input current one

The digital-to-digital conversion 20 is designed to convert the voltage from the output of the differential amplifier 19 to a digital code.

The delay element 21 is designed to delay the control pulses of the A / D converter 20 for the time required to compensate for the signal transmission delay from the output of the first delay element 2 to the input of the A / D converter 20, and when it arrives at the control input of the A / D converter 20 1, its output register is cleared and prepared for the next - 15 following conversion cycle (mode

Cancellation), and upon receipt of

the second - 1) - participates - provides the Transform - mode (position.

The recorder 22 is designed to 20 receive digital information about the state of the sensor and convert it to a readable form. It can also perform the functions of indicating and accumulating incoming information.

The device works in the following way.

The counter 4 counts the pulses coming from the pulse generator 1 to its counting input through the delay element 2. The digital code from the C4et output 4 controls the operation of the switches 12 and 14, which provide connection to the first and second outputs from

temporarily into two loads with which in- razgatel 10 current of the outputs of one of the windings of the sensor, the selected sensor 16.1. At the output of the adder 7

switches 12, 14, or 15, with demagnetizing current pulses coming from the outputs of the current reflector 11, and powering ones from the current reflector 10.

Switches 12 and 14 are designed to connect two windings of one of the sensors 16.1 to a source of demagnetizing current.

The switches 13 and 15 are designed to connect the two windings of one of the sensors 16.1 to a source of supply current.

The switches 17 and 18 are designed to connect the measuring circuit of the device to one of the sensors.

The differential amplifier 19 is designed to amplify the difference in voltage taken from the winding of the selected sensor 16.1, which is proportional to the measured physical quantity.

ten

15

thirty

the digital code exceeds the code at the output of counter 4 by one, therefore the switches 13, 15, 17 and 18, which are controlled by the digital code from the output of the adder 7, provide for connecting the leads of sensor 16 (1-1) to the outputs of the current reflector I1 and the inputs of the differential amplifier 19. Poll all

Sensors I6.1-16.N are conducted sequentially from the 1st to the Nth and then repeated many times, which is necessary during long-term tests, in order to ensure the required accuracy.

during repeated circulations, it is necessary to eliminate the residual voltage on the windings of the sensors 16.1-16, N due to their incomplete demagnetization. Sensors 16.1-16.N are pulsed down.

special shaped current having two sections AB (fast saw) and BC - slow saw (position 26, fig. 2).

In this case, a speed gain is achieved in comparison with powering the sensors with conventional sawtooth current pulses (as in the prototype device due to the forced establishment of a constant voltage on the output of the differential amplifier 19. When the sensors are drilled with the sawtooth current, the windings L1 and L2 are equal respectively:

and, 1, + U ,, L,

di,

t d (A, t) dt.-L, where L, and L are the inductances of the windings

+ A, g,, A, + A, g, t;

., L, -A -t-Aj.rj.t

one

sensor;

r, r-active resistances

sensor windings;

i (t) At - for sawtooth current Since the reflectors 10 and II have the same currents at the outputs, then With the windings of the sensor r, i.e. Because

L,

that

U (L + iL) A + A.r.t iL A + A (L-frt),

1 -AL-A + A (b + r1).

The output voltage of the differential amplifier 19 has the form

l ebi K (U, -Ui) A + A (L + rt) + & LA- -A (L + rt) A,

where K is the gain of the differential amplifier, 19 (DU);

A - steepness of sawtooth current

. (tg angle of inclination),

i.e., the voltage at the output of the remote control 19 determines a constant voltage jump proportional to L. However, the real differential amplifier 19 has a limited bandwidth and its frequency response decreases in the upper 5 {frequency range - 6 dB (the octave, which corresponds to the filter low frequency with parameters CEE. Therefore, the output voltage of the differential amplifier 19 for real

the occasion

II D)

  SG /

where -) Tr Sz - equivalent parameters of the differential amplifier 19;

iJucT the steady-state value of the output of the remote control 19.

From this expression it follows that the output voltage has the second

the term defining the error; l measurement due to transients, the value of which decreases with increasing c.

The relative measurement error is equal to

 . Bb, t) -U, c. .100%. ., 00.

-out

Y9S

It follows that for about 1% 4, 16 R, C, i.e. ADC conversion can be started after tucr after supplying the supply current to,

which is quite large for real measuring amplifiers.

Consider the case of powering the sensors 16.1-16.N with complex-shaped current pulses (position 26, Fig. 2), having 3 sections AB - fast saw, BC - slow saw and DM - discharge (integrator reset). At the section AB, due to the fast-growing condition, a forced voltage setting occurs at the output of the differential amplifier 19, at the aircraft section, the voltage is converted to the digital code ADC 20, because at this time the voltage at the output of the control unit 19 does not change and is equal to:

Ug, 2K-bL A

R

where A is the current steepness in the area of the aircraft

Let us determine the time for setting the output voltage, the input voltage (interval,).

A, -2AL K (l-e) A -2KUL,

(at)

where A, is the current steepness in section AB. From where

A, (- e

fc. ,

)BUT

g

then

moreover, since A

 li-k -

where C is the capacity of the integrator 5;

TO

R

I, is the conversion factor of the voltage-to-current converter 9;

current TsAPZ at receipt on

II1 II.

the first group of inputs i, I is the current of the DAC when it enters the first group of inputs O,

R .C,

I.

 -;

y-: 1., it is obvious that at C and already at I 0.51,

t, О O, 7 1 jC ;, which gives a five-fold gain n; j of the establishment time, according to the prototype.

Formation of current supply pulses; iT chic z is carried out with the help of CLP, generator 5, inverter 6, voltage-current converter 9 and secondly reflector P current,

The duration of the pulses produced by BafMbix by the generator of 1 pulses is set equal to t,, where t, is the length of the section AB (position 26, Fig. 2), and the period following

 .-t-tp, where, is the time of establishment (of

current AB);

t PC conversion time (NS section);

to - time - discharge (plot DM).

I

Determining the outcome of the required fastness and the capabilities of the elements of the device, the value of t. can determine rf current

B i

,; (1st)

where L, is the output current of the DAC for the section AB;

T is a trickle current of an ICPD for the section VS, T-k as the SAP 3 current is directly proportional: ;;; to a code, it is possible to determine which inputs 3 are connected to the delay element 2. If

current

corresponds to the maximum

Input code 11AP N (all units) then T corresponds to the input code M:

(i-e)

All the cool bits of the code M are obg din PTS: the first group and are | to v1; .A1du nopBoi o of the element 2 delay, and ese ;, the initial bits of the KOTS9 f about the output of the group but I rotate the group m, and ::: -o-ixK; I c; l, then the current H i ;; bixoi.iix T; i (-iMier view of the right angle Hbi: - i lnv.n j- В (,; 1 25, fig. 2). Ht K ,,., and fprpciTnpa 5 for example with the T eye of n;: tch: ..; oa and, chiee-T negative lol; .- g; p ;, p ;.). , jр, the intruder 5 in- Beprupvfc - gs tal, therefore for the reverse Hitecp-, l.h chi signal.ppa puimen - eTL n inve; / 1, ip 6.. The voltage at the output of the Innergor - has r,

five

0

0

five

0

five

R

I ...

- Uch, 1stock .t +

U

-t - section of the aircraft

B.

C C

where C is the capacity of the integrator.

The voltage-current converter 9 and the current reflector 11 are used to supply the same current pulses to both windings of the selected sensor.

Upon completion of the conversion from the output of the differential amplifier 19 to the digital code using the A / D converter 20, as well as the registration of the output code by the recorder 22, the impulse input of the integrator 5 receives a pulse from the output of the pulse generator 1 (position 26, Fig. 2 point CJ In this case, the integrator capacitor is discharged and the voltage at its output decreases to zero (part of the LED), Also the sensor supply current and voltage on its windings decreases to zero. With repeated sensor polls due to incomplete demagnetization, an accumulation of error can occur which leads to a decrease in accuracy, therefore, this device uses forced demagnetization of sensors, the demagnetization current coinciding in amplitude and form with the power supply IOKOM (magnetizing) and opposite to it in direction (position 27, fig. 2),

This completely eliminates the accumulation of errors during long-term operation of the device. The sensors are demagnetized using a voltage-to-current converter 8 and a current reflector 10, as well as switches 12 and 14, the control code of which is one less than the control code of the other switches of the device. Upon completion of zeroing of integrator 5 (point D) in the measurement cycle of the i-ro channel, during which (section AB) the sensor 16.1 is connected to the power and measuring circuits of the device using switches 13, 15, 17 and 18, all switches switch The sensor with the number 6 is connected to the measuring and filing circuits (i + +1), and the sensor 16.1 is connected to the demagnetizing circuit with the help of switches 12 and 14. At any time, the sensor is demagnetized, the signal from which was measured in the previous measurement cycle, and when it returns to this sensor in the next survey cycle pejyni.itir, the measurement will not be distorted due to the residual voltage on the sensor windings.

Thus, in this device, as compared with the prototype, the response speed is increased due to the use of forced voltage setting at the output of differential amplifier 19 (in practical implementation of the device, the setting time was reduced by 4.6 times and the total channel measurement time was reduced by 2-3 times) and increased accuracy by eliminating the effect of residual stresses on the windings during multiple sensor surveys and the identity of the measuring channels, since all sensors have a common differential force Spruce 19 converts signals on the sensor windings in the output voltage.

Claims (1)

Invention Formula Multichannel measuring device for differential inductive sensors, s .-: the first switch is open, connected to the first inputs of the respective differential inductive sensors, the second switch is connected to the first input of a differential amplifier connected to the signal input of the analog-digital converter connected by an output to the recorder's input, and a controlling input to the output of the first delay element, a pulse generator, a digital-to-analog converter, uk outputs connected with the control inputs of the first switch, characterized in that in order to improve performance and accuracy of the measurement device, a second delay element incorporated into it, the integrator ,, inverter, first and second converters voltage - current. 0 the adder, the first and second reflections of the current, the third-sixth switch of the switch,;. and the output of the generator is pulse-controlled directly with the integrator's input terminal, and through the second delay element - with the information inputs of the digital-to-analog converter, with the inputs of the first ( 5th delay element and a counter connected by outputs to the first inputs of the adder and to the control inputs of the third switch connected by a signal input to the first output of the first reflector of the current connected by the second output to the signal input of the first mmutator, input through-first voltage converter - current - to the output of the integrator connected by the first input to the output of a digital-to-analog converter, and output through series-connected inverter And the second voltage converter - current to the input of the second current reflector connected to the first and second outputs, respectively with the signal inputs of the fourth and fifth switches, the control inputs of which are connected to the outputs of the adder and the control inputs of the second and sixth switches, the signal inputs of the second switch are connected to the corresponding outputs of the first and fourth switches, the signal inputs of the sixth commutator are connected to the corresponding outputs of the third and fifth switches and to the second inputs of the respective differential inductive sensors, and the output to the second input of the differential amplifier, the third input of each of the differential switches. inductive sensors are connected to the common bus of the device and to the second input of the adder, which is connected by a third input to the input to specify a single signal of the device and control conductive input nif- roanalogovogo preobrp ovatel, five 0 five 0 five