SU1649521A1 - Device to adjust temperature - Google Patents

Abstract

The invention relates to the automation of technological processes and can be used to control the temperature in objects with electric heaters. From & henterium allows to increase the accuracy and stability of temperature control and stabilization In a temperature control device comprising a sensor 1, a binary counter 5 with a digital type setting device 6, a frequency generator 3, the elements And 4. 8, 16, 17 , voltage-frequency converter 2, second counter 9, storage register 10, third counter 11, trigger 12, pulse formers on a positive 13 and negative 14 fronts, frequency divider 15 V period of a high level of pulses from converter 2, a counter 5 filled high frequency pulses from the generator 3. The bit of which is determined by the setting device 6 and, when filled, is then filled through element 8 with the counter 9, the contents of which are proportional to the difference between the set and the current temperatures and which are sequentially copied to the register 10 and the counter 11 for each pulse arriving into the load through the element 17 from the output of the frequency divider 15, the leading edge is delayed by the time inversely proportional to the contents of the counter 11, and thereby the power applied to the load changes . 2 or Ј

Description

The invention relates to the automation of technological processes and can be used to control the temperature in objects with electric heaters.

The purpose of the invention is to improve the accuracy and stability of the device.

FIG. 1 shows a block diagram of the device; Fig 2 - the cyclogram of his work

The device contains a temperature sensor 1 connected to a voltage-frequency converter 2, a reference frequency generator 3, the first element 4, the first counter 5 with a digital temperature gauge

6 as a software switch, an inverter 7, through which the prohibition signal from the output of counter 5 is fed to the input of the element 4. The third element is AND 8, the second counter 9. The storage register 10 with the recording of the parallel code from the output of counter 9, the third counter 11 with preliminary recording parallel code from the output of the register 10. trigger 12, pulse shapers on the positive front 13 and negative front 14, frequency divider 15, the second element And 16, the fourth element And 17, power amplifier 18.

The device works as follows.

ABOUT

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you ate

Temperature sensor 1 in the form of a thermocouple is installed on the temperature control object. An emf from sensor 1 in a voltage-to-frequency converter 2 is converted into a pulse sequence with a frequency proportional to the emf of the thermocouple or, ultimately, to the measured temperature,

The reference frequency generator 3 generates a pulse voltage of a stable frequency, the counters and the register in the initial state are set to the zero state. On the program switch 6, the desired control temperature is set.

The set temperature code on software switch 6 is the preset code for meter 6 on the pre-recorded input.

The device starts to operate when the permitting level is applied. Starting the input of the first element I 4. If there is a permit level, the element 4 passes pulses from the converter 2 and the generator 3, and the frequency of the pulses of the generator 3 considerably exceeds the frequency of the pulses of the converter 2 (500-1000 times) whose duty cycle is chosen to be 100-120. At the moment when the pulse from converter 2 is at a high level, the counter-pulse 5 is filled with reference-frequency pulses.

As soon as the counter 5 is completely filled at the overflow output, a high level appears, which through the inverter 7 locks the AND 4 element on the input and allows the passage of the reference frequency pulses through the AND 8 element to the input of the second counter 9. The counter 9 is filled with the reference frequency pulses. If the duration of the high level of the pulse from the converter 2 is sufficient, then the counter 9 is filled completely and the low level of overflow from the counter 9 is blocked by element 8, the passage of the pulses of the reference frequency is stopped. If the high level of the pulse from the converter ends earlier, then the counter 9 remains unfilled and the low level of the pulse from the converter 2 is reset by the counter 5, and the element 8 is blocked by the low level, the further filling of the counter 9 stops. The negative pulse front from the converter 2 by the shaper 14 produces a short pulse, according to which the output code of the counter 9 is written to the register 10. The positive edge of the pulse from the converter 1 by the shaper 13 produces a short pulse that resets the counter 9 to the zero state

On the course of the divider 15, the frequencies of the divided

a reference frequency with a high level duration tn, and the duration tn is chosen such that

tn N9max r, where MEAh is the maximum size

counter 9;

t is the period of the reference frequency. A low pulse from the output of the frequency divider 15 records the contents of the register 10 into the counter 11 at the input

pre-recording. In this case, the bit size of the counter 11 is chosen equal to the bit width of the counter 9. When the pulse level at the output of the frequency divider 15 is high, the reference frequency pulses through

element And 17 is filled at the input of the direct counting counter 11. At the end of the filling, the output of the counter 11 appears to be a low level, by which the trigger 12 switches, at the inverse output of which the low level is set, and at the forward output - high. By a low level from the output of the trigger 12, the counter 11 is reset on the reset input and the AND element 17 is locked. High level from another trigger output 12

the element 16 is opened and a high level of the pulse from the output of the frequency divider 15 passes through the element 16 and into the power amplifier 18, at the output of which the load is connected. Thus, the positive edge of the pulse from the output of the frequency divider 15 is delayed by the time t3 or by the counting time until the counter 11 is full.

The division factor of the frequency divider 15 is chosen such that the frequency by

the output was 10-50 times the frequency of the converter 2. The temperature control process is carried out by supplying the pulse-width modulated pulses of the required amplitude to the load.

Another low impulse

from the output of the divider 15 frequency trigger 12 is set to the initial state, the element And 16 is locked, the element And 17 is unlocked, there is a process of writing to the counter

11 of register 10 and the counting process is repeated.

In the regulator, two periods are observed.

The first period is the regulator's output.

for the required mode, the second period is to maintain the temperature at the required level. In the first period, when the temperature of the object is low, the duration of the period of the output pulses from the converter 2 is quite large. During this period, the counter 9 is completely filled. The overflow level of the counter 9 locks the input element AND 8, the maximum binary code is set at the output of the counter. This code is then sequentially rewritten into register 10 and with each pulse from frequency divider 15 into counter 11. At the output of counter 11, when the maximum code is set, the fill level is low, trigger 12 switches absent from frequency divider 15, the pulse passes completely through element 16 to the amplifier power 18 and load. As the temperature of the control object rises, the frequency of the pulses at the output of converter 2 increases and the period decreases.

The number of pulses to complete the counters 5 and 9 becomes

N5 + N9max

Trip

g

where N5 is the fill rate of the counter 5, installed on the software switch 8,

Tpr - the duration of the high level of the output frequency pulse from the converter 2

At the same time, the counter 9 is not completely filled and the higher the temperature, the less Tpr and fewer pulses are counted by the counter 9

N9 - - N5

The output code of the counter 9 is sequentially rewritten into the register 10 and the counter 11. Moreover, the fewer pulses will be recorded in the counter 11, the more pulses of the reference frequency are needed before the counter 11 is filled, therefore the edge of the pulses from the output divides the frequency 15 .

The duration of the output pulse t, OUT, in the load is equal to

tebix tn - t3.

The accuracy of temperature maintenance can be estimated as follows. The pulse duration from the converter 2 Tpr is greater than the pulse duration tn from the frequency divider 15 times K, i.e.

ПЈ К;

tn

Tpr

tn - K When the temperature changes, the duration of TPR to DTPr changes, thus forming 5

0

five

0

five

0

leads to

in load

Therefore, the pulse duration at the output of converter 2 becomes equal to Tpr i A Tpr.

The relative change in impulse BUDPR 0

det v. This change causes a relationship.

a dramatic change in the duration of the pulses entering the load, which is expressed as

A TPR „DTPR

with. - k. - p.

tnI pr

Thus, the relative change in the pulse duration at the output of preDTPr

TPR change the width of the pulses, giving KV AB. those. at

Tpr

K times big.

It follows that the accuracy of temperature maintenance is determined by the choice of the ratio of the pulse durations from the converter and the frequency divider 15. In practice, this ratio is 20.

Setting the temperature in the digital code Digital information processing in the control process allows you to quickly and accurately set the required control temperature and to obtain high accuracy of temperature maintenance in the control process and to ensure a fast and stable process of reaching the specified mode Information in the digital code allows you to use computers and microprocessors and other control devices to control the quality of regulation and obtain documentation on the process of regulating and maintaining temperature

five

0

five

Claims (1)

The invention includes a temperature control device comprising a series-connected temperature sensor, a voltage-frequency converter, a first And element and a first counter with a digital setting device connected to its installation inputs, and a frequency generator, And elements, a control unit, and a power amplifier with load output, characterized in that, in order to increase the accuracy and stability of the device, it contains a frequency divider, pulse shapers on the positive and negative f A contact, an inverter, and a control unit are made as a serial connection of a second counter. the storage register, the third counter and the trigger, the direct output of which through the second element I is connected to the input of the power amplifier, the inputs of the pulse formers on the negative and positive edges connected to the output of the voltage-frequency converter, and the outputs respectively to the input of the Recording register and Resetting the second counter, the counting input of which through the third element I is connected with the output of the reference frequency generator connected to the second input of the first element I, the third input of which through the inverter is connected to the output overflow of the first counter and directly with the second input of the third element And, the third input of which is connected to the overflow output of the second counter, the fourth input of the first element I is the device Start input, the frequency divider input is connected to the output of the reference frequency generator, the output is to the first input of the fourth And element, the second trigger input, the Record input of the third counter and the second input of the second element And, the second input of the fourth element And connected to the first input of the third element And, the third input - with the inverse output of the trigger and the input Reset the third counter, and the output - with the input of the direct counting third th counter.