SU805274A1 - Temperature controller - Google Patents

Description

one

This invention relates to a technique for measuring and controlling temperatures.

An analogue temperature control device is known, consisting of a temperature sensor, a driver unit, a control unit, a thyristor unit. The temperature of the object controlled by such a device is determined by the magnitude of the electrical voltage taken from the master unit. This voltage is compared with the thermo-emf of the temperature sensor, determined by the current temperature of the object, and with the help of an adjustable unit and a thyristor unit, controlled by the difference in thermoEMF and voltage from the master device, the electrical power at which the value of thermo-EMF becomes equal to the voltage from the driver 111

The disadvantage of such a device is the difficulty of using it in the automated production, since the master unit is an analog node whose control, for example, with the help of the control panel, requires the introduction of code-analog converters and the corresponding matching blocks. In addition, analog devices are characterized by limited accuracy in time due to aging of elements. Such devices are most often used as digital devices.

The closest to the offer is a digital thermostat with a digital control designed by the DCF to maintain the temperature of the object.

0 at a predetermined level, consisting of a temperature sensor and a unit for converting an object's temperature value to a digital code, which includes a temperature to frequency converter

5 and a digital counter, a digital driver, a digital comparator, a unit for changing the temperature of an object, where the output of the temperature sensor is connected to the first input of a digital comparator, the digital driver’s output is connected to the second input of the digital driver, and the digital comparator output to the second input of the digital comparator. It is connected to the input of the unit for changing the temperature of the object.

The device works in the following way.

The current value of the object temperature is measured by a temperature sensor, the signal from which is converted by the conversion unit into a digital code and fed to the first input of a digital comparator, where it is compared with the specified temperature value of the object supplied to the second input of the comparator with the set ({(its block. From the output the comparator detects the difference of the input digital signals, which is fed to the input of the unit for changing the temperature of the object, which, depending on the sign of the difference, increases or decreases the temperature of the object f2j.

The disadvantage of this device is a reduction in the accuracy of regulation during operation, which determines the basic stability of the calibration characteristic of the sensor, which was removed before installing it on the object.

tl)

(Tn.),

TGR is the value of temperature grad. POBKHJ

sensor signal value

gr, with the corresponding value of TGR

In accordance with this characteristic, the current (measured) value of the object temperature is determined.

The calibration characteristics of real thermal resistance sensors, thermocouples, etc.) vary over time depending on the operating temperatures (measured by the temperature). Especially these deviations are great when regulating high-temperature objects, for example, in the production technology of semiconductor elements, where high demands are placed on the accuracy of regulation, in particular, in the production of thin-film elements, where the temperature should be set to an accuracy of a few percent. But during operation, the calibration characteristic of the sensor can vary by a few percent.

0 The table shows the change in the calibration characteristic from the initial thermocouple type BP 5/20, which is widely used to work in high-temperature objects, depending on the time of operation and the temperatures at which they worked.

As can be seen from the table, the error of temperature measurement by a thermocouple, determined from the calibration curve from the Initial, can have a significant value. For example, at a temperature of 2000 ° C already after 100 hours of operation, the error is.

The purpose of the invention is to increase the accuracy of regulation during operation of the device. .

The goal is achieved by teM that a timer, the first memory element, the delayed serially connected element, the averaging unit, the first function converter, are entered into the well-known Device, which contains a serially connected master unit, a digital comparator and an actuator, as well as a serially connected sensor and a digital converter. the second memory element and the adder, as well as sequentially

connected memory block, second function converter and third

45 is a storage element whose output is connected to the second input of the first functional converter, the third input of which is connected to the output of the memory unit, and the fourth input 50 to the timer output connected to the second input of the averaging unit and the second input of the second functional converter, the third and fourth inputs of which connected respectively to the output of the averaging unit and the output of the first storage element, the input connected with the output of the first functional converter, and the input of the adder is connected to the output dy digital converter, and an output - to the inputs of a digital comparator, the delay element and the averaging unit.

The drawing shows a block diagram 65 of the proposed device. The temperature control device contains a master unit 1, a digital comparator 2, an executive element 3, a sensor 4, a digital converter 5, an adder 6, a delay element 7, an averaging block 8, a first functional converter 9, a first storage element 10, a second functional converter 11, timer 12, memory block 13, second and third memory elements 14 and 15. The device operates as follows. The current temperature value of the object Tf is measured by sensor 4, the digital code T is converted by converter 5 and fed to the first input of the adder 6. Due to the presence of error due to a change in the calibration characteristic from the initial T {T4-LT4., (2) where Tj - the true value of the temperature of the object: dt - the current value is 1in the deviation of the calibration characteristic from the initial one. At the second input of the acquiring b, the correction is supplied with the correction ДТчвдТ ± 8, (3) where "ДТ / -; error of determination of LT4, which is determined by the accuracy of the blocks 7-13. At the output of the ad, the value, is formed. . T4 T "-Ali- -dT S Ti 1B C) fC output of the adder b, the value T / is fed to comparator 2, and the second input of the comparator is supplied with the value of the specified temperature of the object T".} Ads of block 1. Comparator 2 compares these values and produces a controlling effect E on the input of element 3, which, depending on the magnitude and sign of E, increases or decreases the temperature of the object so that the value of E is minimal. The definition of the dT amendment is as follows. The timer 12 generates the value of the time intervals DT4, which I apply to the inputs of the averaging unit 8 of the first fuctional converter 9 and the second functional converter 11. The measured object temperature Ti from the output of the adder b is fed to the first input of the averaging unit 8, to the second input of which is fed T through the delay circuit on dTi, the value of the measured temperature in the previous moment of time - T .. At the output of averaging unit 8, the average temperature of the object is formed, the time interval ATi. T. (5) Mejr 5 This value is fed to the inputs of the functional transducers 9 and 11, and the static characteristic for this type of sensor from memory block 13 is also removed. (tt), (6) where AT is the deviation of the calibration characteristic of the sensor from the initial one; t is the sensor operation time from the start of installation} T is the temperature, when the sensor is working. This characteristic can be obtained by interpolating tabular values determined when testing a series of sensors of this type, for example, thermocouples, thermistors. The functional conversion 9 determines the magnitude of the variation of the calibration characteristic uTi for the period (by the formula (b) DT DT f (tjTcpi), 7) where t is the impressive sensor aging (wear) time determined by the functional converter 11 and stored in element 14 as in the device (sensor) operation time, also when the device is temporarily disconnected .. From the output of the functional converter, 9 dT-i is fed to the first storage element 10, where it is delayed by the value ut4. The ATi summation in order to determine the suldalar deviation of the calibration characteristic from the initial one occurs according to the fordout DToB1D 51 LT. served on the second input of the element Y. From the output of the element 10, the correction in the next moment of time is fed to the input of the functional converter 11, the second determines the relative aging time of the sensor. This time is determined on the basis of the theory of reliability, on the basis of which the wear of an element at a given time depends on the amount of the used resource in the past and does not depend on how this resource was developed. The functional transform 11 realizes the inverse function of formula (7) according to the values of DT. and TcdD ti -F {AT4-Tor.4) (9) The e-o value is fed to the outputs of the converter li through element 15 to the input of the functional converter 9. When the device is disconnected by wiring, the temperature and object control in the elements 15, 10 and 14 are kept t, ff and dT. / by which

Claims (1)

Claim A device for controlling the temperature, comprising a serially connected master unit, a digital comparator and an actuating element, as well as a serially connected sensor and a digital converter, characterized in that, in order to increase the accuracy of regulation during long-term operation ^{of the} device, it contains a timer, the first memory element, series-connected delay element, averaging unit, first functional converter, second "memory element and adder, as well as a separately connected memory unit, a second functional converter and a third storage element, the output of which is connected to the second input of the first functional converter, the third input of which is connected to the output of the memory unit, and the fourth input - with the timer output associated with the second input of the averaging unit and the second input the second functional Converter, the third and fourth inputs of which are connected, respectively, to the output of the averaging unit and the output of the first storage element, the input associated with the output ne Vågå functional converter, and an adder input connected to the output of the digitizer, and the output - to the inputs of a digital kompa30 Rathore, delay and averaging block element.