SU1667031A1 - Thermoelectric system for regulating temperature - Google Patents

Abstract

The invention can be used to programmatically control the temperature with a thermopile. The purpose of the invention is to increase the speed of the temperature control system. The system contains an object temperature control loop and a thermopile current control loop. When the object temperature is close to the set point, the thermopile current is determined by the temperature control loop. During the transient process of heating an object, the current through the thermopile is set by the current setter at a constant level determined by the allowable power dissipation in the thermopile. During the transient cooling process, the current through the thermopile changes depending on the change in the signals of the temperature sensors in thermal contact with the corresponding thermopile faces. This makes it possible to produce on the working edge of the thermopile, which is in thermal contact with the object, at each time point of the transient process the maximum possible cooling capacity, which reduces the cooling time and leads to an increase in system performance. 2 Il.

Description

The invention relates to automatic control systems, thermoelectric instrument making, can be applied for software temperature control.

The purpose of the invention is to increase the speed of the temperature control system of the object.

FIG. 1 shows a diagram of a thermoelectric temperature control system; in fig. 2 - single-stage thermoelectric battery design.

The thermoelectric temperature control system contains a series-connected temperature sensor 1, which is in thermal contact with the object 2, the temperature of which is regulated and the computing device 3.

The first output of the computing device 3 is connected to the control inputs of the first 4 and second 5 switches, and the second output is connected to one of the inputs of the comparison device 6. The system contains a third switch 7, the first input of which is connected to the second output of the subtracting element 8 and the other input of the comparison device 6, the control input with the output of the comparator device 6, and the output with the input of the power amplifier 9. The first output of the power amplifier 9 is connected to the first input of the first 4 and the second input of the second 5 switches, and the second output to

ABOUT

about

Vj

ABOUT

WITH

bus zero potential and the first output current sensor, made in the form of a resistor 10. the second output of the resistor 10 is connected to the second input of the first 4 and the first input of the second 5 switches and one of the inputs of the subtractive element 8. The system also contains a single-stage thermopile 11, the working face of which is in thermal contact with the object 2, the first and second terminals of the thermopile 11 are connected to the outputs of the first 4 and second 5 switches, respectively. In addition, the system contains a fourth switch 12. The first input of which is connected to the output of current generator 13. The second input is connected to the output of current sensor 14, the control input is connected to the first output of computing device 3, and the output is connected to another input of the subtracting element 8.

The input of the adjustable current setting device 14 is connected to the terminals of the temperature sensor, which is used as a thermistor 15, which is in thermal contact with the working edge of the thermopile 11.

An adjustable current setting device 14 is provided at an operational amplifier 16, the non-inverting input of which is connected to a terminal with potential E, the inverting input through a resistor 17 is connected to a zero potential bus, and is an input of a current setting device 14, and the output of the amplifier 16 is an output and input current setting device 14 .

Adjustable current setter realizes the following functional conversion

Uyn (Ј) RoT,

where a, R is the value of thermo-EMF and the thermopile electrical resistance;

Ro is the resistance value of the current sensor;

T is the temperature value of the sensor of the working edge of the thermopile.

In this case, a single-stage thermopile 11 is used in the system, the non-working face of which is in thermal contact with the heat exchanger 18, which has an infinitely large heat capacity (Fig. 2).

The system works as follows.

The change in the temperature of the control object 2 is converted by the temperature sensor 1 into an electrical signal at the input of the computing device 3. The computing device 3 processes the received information and generates control signals at its outputs that correspond to a certain control law. Moreover, the signal at its first output, switching the first 4 and second 5 switches, controls the direction of current through the thermopile 11 so that the temperature of the object 2 tends to the specified value. The signal at the second output of the computing device 3 controls the amount of current through the thermopile 11, depending on the temperature parameters

0 regulated process. With a significant discrepancy between the controlled and the set temperature, this control signal reaches a large value. When its value exceeds the signal value by

5 the output of the subtracting element 8, at the output of the comparator 6, a signal is generated, disconnecting the output signal of the computing device 3 from the input of the power amplifier 9 and connecting the output to it

0 subtractive element 8.

In this case, the negative feedback on temperature is interrupted in the controller and negative feedback on the thermopile current 11 is established.

5 When at the first output of the computing device 3 there is a signal that commutes the current in the thermopile so that it operates in the heating mode, this signal is fed to the control

0 the input of the fourth switch 12 connects to the other input of the subtracting element 8 the output of the current setting unit 13. Due to the negative feedback from the second output of the resistor 10 to one of the inputs of the subtractive element 8, the current through the thermostat 11 is automatically set to

the level set by the setpoint current 13. For

speed increase this value

is set to the maximum possible with

0 taking into account the limitation on the maximum allowable temperature of the thermopile working edge.

When the thermopile current is disconnected from a predetermined, for example, when the supply voltage of the power amplifier 9 or thermo-emf at the terminals of the thermopile 11 is changed, the voltage across the resistor 10 will also change. This will cause such a change in the signal at the output of the subtracting element 8,

0 at which the output current of the power amplifier 9 will take the initial value determined by the magnitude of the signal at the other input of the subtracting element 8.

When forming computing device 3 at its first output of the cooling signal, the latter switches the switch 12 in such a way that the output of adjustable current setter 14 is connected to another input of computing element 8. Due to negative feedback

over current, the system starts to operate in the thermopile current tracking mode 11 in accordance with the change in the signal at the output of the current sensor 14 being regulated.

Current. flowing in a thermopile, it cools its working face. The change in its temperature is converted by the thermistor 15 into resistance according to the law

RT - Ro + a 0

where RO is the resistance of the thermistor at zero temperature, ° С;

0- temperature of the working edge of the thermopile 11. ° C; 15

a is a constant coefficient.

In this case, the output voltage of the operational amplifier 16 is determined by the expression

Un-Eo (1 + - {Ј-).

and „Ео (1 +

RO + a0

R17

),

where Eo is the voltage at the non-inverting input of amplifier 16;

Ri is the resistor of the RIT resistor, or with (1) 25

The magnitude of the current I of the thermopile, determined from the equation of the following system

Un IRio,

where IRio is the voltage across the reference resistor Y.

I §о.а 1 RioRn

With RiT-aTo-Ro and

where RTB is the thermopile resistance;

a - coefficient of thermoelectric material EMF;

T0 - zero temperature, in ° C translated to K.

i gTi

where TI-TD + 0 is the temperature of the working edge of the thermopile. TO.

At the end of the transient temperature setting process, when its value approaches the preset value, the value of the control signal at the second output of the computing device 3 begins to decrease in accordance with the selected control law. At the moment when the magnitude of the signal at the second output of the computing device 3 becomes less than the magnitude of the signal at the output of the subtractive element 8, at the output of the comparison device 6 a signal is generated that turns off

5 Yu

15

20

25

thirty

35

40

45

50

55

from the input of the power amplifier 9, the output of the subtracting element 8 and the second output of the computing device 3 connected to it, i.e. Negative current feedback is terminated and negative feedback is established according to the temperature parameters of the control object 2. The current value is controlled by the control signal from the second output of the computing device 3, depending on the parameters of the process of changing the temperature of the object 2. This allows the various temperature control algorithms to be implemented in the computing device 3.

Disabling negative current feedback after the temperature has reached the mode prevents the possibility of auto-oscillations in the system.

Claims (1)

A thermoelectric temperature control system comprising an object temperature sensor connected in series and a computing device, the first output of which is connected to the control inputs of the first and second switches, a third switch, the first information input of which is connected to one of the inputs of the comparison device and the second output of the computing device, the second information input is to the output of the subtracting element and another input of the comparator, and the control input is to you One comparison device, a power amplifier whose input is connected to the output of the third switch, a first output to the first information input of the first and second information input of the second switch, a current sensor, the first output of which is connected to the second output of the power amplifier and a zero potential bus, and the second pin to the first input of the subtracting element, to the second information input of the first and the first information input of the second switch, a single-stage thermoelectric battery whose working face is in thermal contact with the temperature control object, and the non-operating one is with a heat exchanger, the first and second terminals of the thermopile are connected to the outputs of the first and second switches, respectively, and the current setting device, which is different from that. in order to increase the system speed, a temperature sensor is introduced into it, which is in thermal contact with the working edge of the thermopile, the terminals of which are connected to the control input of an adjustable current knob, and the fourth switch, the computing device, the output is from the first information input of which with the input of the subtracting element, and is connected to the output of the current setting unit, the control of the second information input is with the output the first input is with the first output of the current setting knob. t; computing device, output - with Fig. / Kyhoduler-switch By the way of the second leremutik  The code will be numerically so in order cm yes  cm roist- / 8a conversion inputs