SU1352507A2 - Digital measuring and processing system - Google Patents

Abstract

This invention relates to automation and computing. The invention can be used in automated control systems, information-measuring systems, automated measuring complexes. The purpose of the invention is to improve the measurement accuracy of information-measuring systems by using a piecewise linear approximation of the transfer characteristics of sensors of measured values. The system consists of sensors 1, first 2 and second 8 switches, memory blocks 7 and 9, measuring unit 3, analog-digital converter 4, adder 5, address counter 6, registering unit 10. A new device is a digital-to-analog converter 11 and a comparator 12, which makes it possible to vary the conversion factor of the analog signals depending on the number of the approximation area and thus reduce the influence of the non-linearity of the transfer characteristics of the sensors on the measurement error. 1 hp f-ly. 2 Il. with (L with JV Yu J N)

Description

one

The invention relates to automation and computing, can be used in test automation and control systems of industrial facilities and is an improvement of the invention in accordance with the author. St. No. 877565.

The purpose of the invention is to improve the accuracy of the system.

FIG. 1 shows the structural scheme of the proposed system; in fig. 2 is a graph of the approximate transfer characteristic of the sensor. The system (FIG. 1) contains M sensors 1, first switch 2, measuring unit 3, analog-to-digital converter 4, adder 5, address counter 6, additional memory block 7, second switch 8, N memory units 9, registering unit 10 digital-to-analog converter 11 and comparator 12, reference voltage source 13, discrete voltage divider 14, threshold voltage source 15, comparison circuits 16, NOT elements 17, And 18 elements.

The graph of the transfer characteristic of the sensor (Fig. 2) approximates the piecewise linear curve based on the following assumptions.

The output signals of sensors 1 are brought to a single range of changes in the output signals of measuring unit 3, controlled by signals from an additional memory block 7. The specified range is divided into L subdia with boundary values yj

lie about

puzzles

, about

 one

(x ° (x °; ur,

about

Ur

(y) form a break point approximation} of the curve. The initial value of the transfer characteristic is indicated by. In order to simplify the comparator circuit, 12 boundary values of y °, y °, ..., y ° for all sensors are selected identical, and the number of corresponding values of physical quantities x, x °, ..., x ° for g The i-th sensor is determined by its transfer characteristic and the corresponding values of the signals y. corresponds to a series of values of measurable quantities x, x °, ..., x. Corresponding pairs of coordinates

the transfer coefficient measured by the discrete values of the coefficient block 3. If the output of the blocks of the measuring block 3. ka 3 yielded the result y, found the identification symbol of each subscript in the kM; tazone (y, y when setting up the system; k 1, 2, ,,, L), then in COOT- we are based on the transfer characteristic 1352507

inti

according to FIG.

-sg

to

p-1

P

uo

 I-f

- (y,

hog

t k.1

bi У5

uo

 1t-f

- X

or k-.l

OR

Ch

 a2

 Where

but,

R

k-1

t--

bl

 , 2

1s-1

- X

k-1

- constants

approximations of the k-ro subrange of the rth sensor, determined by the transfer characteristic of the rth sensor and the corresponding transmission coefficient of the measuring unit 3.

Each of the L subbands corresponds to one of the L outputs of the comparator 12 and one of the L control inputs of the additional memory block 7. For all sensors, the systems precompute the a constants. , B, for each of the L subbands. When setting up a constant system

35 is written into the corresponding memory cell of block 7. The contents of the memory cells of block 7, except for the values of the constants a,

l ;.

are also simvods with. channel identifications, which allow identifying, by the j-th channel number, the type of the rth sensor, the need for the processing information operator, as well as the required transmission coefficient of the measuring unit 3. Thus, the total number of memory cells of the unit 7 should be not less than M (2L + 1).

The maximum required number of binary code constants alj, b j | can be n + 1, where n is the number of bits of the output code of the ADC 4. The maximum number of values that identification symbols can take is not more than PN, where P is the number

ticks of the sensor 1 selected for this channel, the transmission coefficient of the measuring unit 3, as well as the information processing operator required for this channel. The number of main blocks 9 of memory corresponds to the number of different processing operators, and the contents of the memory cells of block 9 are the values of the measured value depending on y - f - (N. B), where y - is the result of measurement by analogy number; f; - the conversion operator of the memory block 9 with the number i; NT is the current (working) reference code A1SCh 4; B

Vf

 - the value of the constant from the additional memory block 7 for the measuring channel with the number j, in which the signal y received the value in the subband with the number j. The maximum required number of memory cells of block 9 for the implementation of the system can be no more than 2

The system works as follows

When setting the address of the measuring channel, the corresponding signal from the first output of the counter 6 is fed to the control input of the first switch 2 and to the additional memory block 7.

8 the address block of the memory block 7, this signal is the address of the memory cell. The content of which (identification symbol) is fed to the first output of memory block 7. In this case, the identification symbol is input to the sensor type assignment of the measuring unit 3 and to the control input of the second switch 8, which switches the corresponding main unit

9 to the output of the adder 5. The signal from the second output of the counter 6 is fed to the control input of the measuring unit 3, setting the necessary mode of its operation. The analog sensor of sensor 1 through the first switch 2 is fed to the information input of the measuring unit 3, from the output of which the measurement information signal is fed to the inputs of the ADC 4 and the comparator 12. In the comparator 12, the measurement information signal is compared with threshold values / voltages, as a result At one of the L outputs of the comparator 12, the signal of the corresponding k-1 subband appears, which arrives at one of the L control inputs of the additional memory block 7 and allows the signal from the first output to pass.

the progress of the counter 6 addresses to the corresponding address decoder of the memory cells of block 7, which stores the constants a and b j of the k-ro subband. Contents of a selected pair of cells storing

ten

20

25

40

constants

thirty

and

from ,, j, arrives responsibly to the third and second outputs of the additional memory block 7 and then to the input of the digital-to-analog converter (DAC) 11 and the second input of the adder 5. The voltage from the output of the DAC 11 proportional to the constant code a) (, arrives at the reference 15 ADC input 4, set the ADC transfer coefficient proportional to the slope of the direct, approximating the transfer characteristic of the sensor in the kM subband.

The signal of the measurement information converted by the ADC 4 into digital form is fed to the first input of the adder 5, from the output of which the discrete signal equals the sum of the signals received at its inputs from the additional memory block 7 (the signal Lp and from the ADC 4 (signal)) the switch 8 to the input of the memory block 9. The memory cell of the block 9 corresponding to the output signal of the block 5 is excited, its contents as a measurement result in the required form for use are input to the recording blog 10.

Thus, the connection of the reference input of the A / D converter 4 with the output of the D / A converter 11, which is controlled by the comparator 12 through the memory power supply unit 7, stores the approximation constants of the transfer characteristics of the sensors, allows to take into account the variation of the nonlinearity parameters of the transfer characteristics and thereby increase the measurement accuracy.

The proposed device, in comparison with the known, is characterized by high measurement accuracy, which is provided by a piecewise linear approximation of the transfer characteristics of the sensors, by remembering the approximation parameters for each of the linear sections and using these parameters to determine the true values of the measured values,

The known device uses linear approximation of transfer characteristics with only one approximation parameter memorized.

45

50

55

tion - the initial values of the transfer characteristic. The method of linear approximation due to lower informativity as compared to the piecewise linear approximation method cannot effectively compensate for the measurement error due to the spread of transfer characteristics parameters, in particular, nonlinearity parameters.

Claims (2)

1. Digital measurement and processing system according to the author. St. No. 877565, in contrast to the fact that, in order to improve the accuracy of the system, a comparator was entered into it, and a digital-to-analog converter, the output of the measuring unit was connected to the input of a comparator, the outputs of which are connected to the additional address inputs of the memory unit, an auxiliary. data outputs which through a digital-to-analog converter is connected to the control input of an analog-to-digital converter. . 2. The system according to claim 1, that is, that the comparator contains a source of threshold voltages, a group of comparison circuits, a group of elements NOT and a group of elements AND, the comparator input connected to the first inputs In comparison circuits, each output of a source of threshold voltages is connected to the second input of the corresponding comparison circuit, the output of each comparison circuit, except the first, is connected to the first input of the corresponding AND element and through the corresponding NOT element to the second input of the subsequent AND element, output of the first circuit comparing s is one of the group of outputs of the comparator outputs, the outputs of elements and outputs are other groups comparator outputs. /one fi & 2 Editor M. Andrushenko Compiled by I. Alekseev Tehred M. Khodanich Proofreader L. Pilipenko Order 5567/49 Circulation 671 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4