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67L100: What are the functions of temperature regulators ?

Mar 17, 2017 02:19

I read an electronic magazine in which there is a report on the functions of temperature regulators, just like this: http://www.kynix.com/Detail/2182/67L100.html. After reading, I became interested in temperature regulators, so I searched some related information about this topic, but to my much disappointment, it is not specific at all. Thus today, I come to this forum to turn to you to discuss my ideas are appropriate.

Here are the following understandings:

The temperature regulator controls the temperature of the control object to the desired temperature. This process is temperature control.

Temperature regulators have such functions:

● Two-position action (switch action)

The temperature control of the electric heater or iron is the switch control, that is, if the actual temperature is higher than the set value to turn off (OFF) electric power of the furnace wire, if the set value is low (ON) electric wire power supply. In this way, the OFF / ON control based on the measured temperature is called a two-position operation or a switch (OFF / ON) operation for the set temperature.

Control is simple, the disadvantage is to produce oscillation.

● Proportional action (P action)

And outputs an operation amount proportional to the magnitude of the deviation between the set value and the measured value.

The proportional band is set at the set value, and once the measured temperature enters the proportional band, the operation amount is gradually reduced.

The temperature in the proportional band to find the balance point tends to be stable, but the measured value and the set value is very consistent.

Set the temperature and stability of the temperature deviation is called residual deviation.

● integral action (I action)

Residual deviation occurs with proportional action. The residual motion is eliminated by the integral action (I action).

The integral action is the area of ​​the output deviation (the difference between the set value and the measured value) and the time at which the deviation occurs, that is, the size of the integral value.

In view of this, as long as there is deviation, integral action in order to eliminate the deviation from the role, and then eliminate the residual bias.

The strength of the integral action is expressed as the integral time. The time elapsed when the output (operation amount) generated by the integral action is equal to the output (manipulated variable) of the proportional motion product is called the integration time.

The shorter the integration time, the stronger the integral effect. The longer the integration time, the weaker the integral effect.

If the integral effect is too strong, it is prone to oscillation, instability.

● Differential action (D action)

Is controlled in accordance with an operation amount proportional to the speed at which the deviation (set value and the measured value) occurs, and the operation for preventing the deviation becomes greater than the actual operation is called the differential operation (D operation).

The strength of the differential action is expressed by the derivative time. The time elapsed when the derivative time is the difference between the output (the manipulated variable) generated by the differential operation and the output (manipulated variable) generated by the proportional action is called the derivative time.

The longer the derivative time, the stronger the derivative effect. The shorter the derivative time, the weaker the derivative effect.

If the differential effect is too strong, even if the variation of the deviation is small, there is a large output change, oscillation occurs, and unstable.

● PID action

PID action is a combination of proportional action, integral action, and differential action. PID adjustment instrument picture PID adjustment instrument picture With the proportional action can be obtained without oscillation of the stability control results, with the integral action to eliminate residual bias, with differential action to improve the impact of external chaos.

Applicable to the invalid time is greater than the adjustment (on the red) large occasions.

Control the type of action

● Positive and reverse action

Positive action is when the actual temperature is higher than the set value of the occasion, increase the amount of operation.

Positive action for cooling control.

The reverse action is when the actual temperature is lower than the set value, the operation is increased.

Reverse action on heating control.

● Heating and cooling control

Control sub-heating and cooling control.

By going to a temperature controller can be heated and cooled two kinds of operation.

● Position proportional control

In the control of the controllable motor, the opening degree of the controllable motor (the position of the resistance scale) is input and the control signal is output. Also equipped with a corresponding "no resistance scale" controllable motor temperature controller.

● cascade control

It is effective for objects with a large time delay between the part where the temperature is to be controlled and the heat source.

The control output of the primary controller (master) is input as a remote controller for the secondary controller (slave).

The secondary controller controls the temperature of the heat source while correcting the temperature setpoint with the control output of the primary controller.

● Manual control

Not through the controller for automatic control, but with the manual operation to change the output control.

For start-up of process control, test run and so on.

● PV bias

In the measurement input plus the value set with PV bias, correct the measurement input.

Used to correct the deviation of the various sensors or deviations with the measured values ​​of other instruments.

Example: When measuring the temperature of the same point with two temperature gauges, the measured value is

Temperature controller A: 200 ℃

Temperature controller B: 198 ℃

If the PV bias is set to + 2 ° C in the temperature controller B, the displayed value is:

Display value = measured value + PV value

= 198 ° C + 2 ° C = 200 ° C.

● Digital filtering

Used to reduce the input clutter interference. Equivalent to a delayed CR low-pass filter.

The time constant of the filter is set according to the characteristics of the control object and the clutter level, and the influence of the input clutter can be suppressed.

If the time constant is too small, the filtering effect is not obtained. If the time constant is too large, the responsiveness deteriorates.

● cold junction temperature compensation circuit

The thermocouple generates the corresponding thermoelectromotive force based on the temperature difference between the meter terminal and the measuring point.

The temperature of the terminal part is the temperature of the room where the meter is set, so that only the thermoelectromotive force corresponding to the temperature difference between the instrument terminal and the measuring point is generated.

Cold junction temperature compensation circuit is to detect the room temperature, the room temperature part of the thermoelectromotive force coupled with the compensation, so that the temperature corresponding to the temperature of the thermoelectromotive force.

● open squares

In the case of measuring the flow rate, when the differential pressure flow meter is used, the output signal Δ, P (differential pressure) and the flow rate (Q) generally have the following relationship:

Q = α√ Δ P

For example, the flow rate (Q) can be obtained by opening the output signal Δ, P from the flow meter.

● Remove PV low input

In the case of open square calculus, even when the input voltage is small, even if the variation of the differential pressure is small, it will cause the measurement flow to change drastically or cause instability due to the input clutter. In order to avoid the above phenomenon, the measurement of the Δ P1 the following part of the function is zero.

● Set the limiter

The function of setting the setting range of the setting value.

● Set the rate limiter

Set the function of changing the set value per unit time when the set value is changed.

It is used to change the setting value without wanting to output the change of the stroke, or for the case of simple program control.

● Multi-storage area function

A function of registering a plurality of parameter sets such as a set value (SV), a PID constant, an alarm set value, a proportional band (P), an integration time (I), and a derivative time (D) in a plurality of memories.

The number of registers can be registered as the number of memory, can log 8 groups of occasions called 8 memory.

Call the corresponding memory (area) for control as needed.

You can simplify the cumbersome setting changes.

● Remote setting

Set the value (SV) with the analog signal from the outside.

· RS magnification

For the remote set value multiplied by the function of the magnification.

• RS bias

The value obtained by adding (subtracting) the RS offset for the remote setpoint is the set value.

About control

● Agile PID control

PID control is a constant control result by setting the constant of P (proportional band), integration time (I), and derivative time (D), and is now widely used. However, the shortcomings of this PID control are:

If the PID constant is set for the "corresponding response", the "corresponding response" is set to deteriorate. On the other hand, if the PID constants are set so that the response to the " Outside the chaos of the response "bad.

The agile PID control can be selected from the shape of Fast, Medium, and Slows of the three "correspondingly set responses" based on the PID parameters set in the "corresponding response".

The three response shapes are called control response parameters. If the response speed is selected, select "Fast" and "Slow" if no overshoot (upper) is generated.

● Automatic calculation (AT)

Automatic calculation (AT) is the function of automatically setting the optimum PID constant for the set temperature.

Automatic calculation can be from the power after the temperature, the control of any state of stability began.

● AT bias

The AT bias setting is the case where the measured value (PV) does not exceed the set value (SV) for automatic calculation.

If the AT offset is set, the setting value (SV) for the automatic calculation can be changed, that is, [AT point].

● Control state judgment type self-calculation

When judging the control has been chaotic occasions, self-calculus function work.

In the normal control does not implement self-calculus, taking into account the trust temperature will be a stability and stability.

● RFB (Reset Feed Back) limiter

When the deviation between the measured value (PV) and the set value (SV) continues for a long time, the PID calculation result will exceed the effective range (0 to 100%) of the operation amount. In particular, the integral (I) output value is greater than necessary, even if the deviation becomes smaller, the implementation of the amendment action is also slow.

RFB limiter is the time when the PID calculation result exceeds the limit point (100%), in order to make the PID calculation results often within the effective range of the part of the feedback into the integral value, so that the results can be maintained at the limit point Correct action.

Arw (Anti Reset Windup)

In the case of PID control, if the integral (I) action is activated from the start of the control object, a large overshoot occurs.

ARW is a function that suppresses the overshoot by limiting the effective range of the integral action (I). The integral action is only effective when the residual deviation is eliminated, so that the range in which the integral action is effective in the proportional band can be suppressed to a minimum.

About the alarm

● deviation alarm

Deviation [Measured value (PV) - Set value (SV)] Alarm state when alarm setting is reached.

The movement of the alarm setpoint changes with the set value.

● Enter the value of the alarm

The alarm value is set when the measured value (PV) reaches the alarm setting.

● Setpoint alarm

Set value (SV) to alarm state when alarm setting is reached.

● Alarm action gap

When the measured value (PV) is near the alarm set value, the alarm output is repeatedly turned ON and OFF due to the drift of the input value. By setting the alarm action gap, it is possible to prevent ON and OFF.

● Alarm standby action

The so-called standby operation means that even when the measured value (PV) is in the alarm area until the measured value is reached (when the power supply is turned on or when the operation mode is switched from STOP to RUN or when the set value is changed PV) from the alarm area before the alarm function is invalid.

※ Please note that some of the instrument call standby action, is to include change set value (SV) of the standby action of the occasion. While the standby action does not include the standby action to change the set value (SV).

● Alarm delay timing

The alarm delay timing means that the measured value (PV) becomes an alarm state even after the alarm has been set to the alarm area.

● Alarm lock

Alarm lock is the function that maintains the alarm status once the measured value (PV) has entered the alarm area even if the measured value (PV) is again off the alarm area.

You can unlock the alarm with the front operation key or the external contact.

● Excitation / non-excitation of alarms

• Excitation alarm: When the alarm condition is on, the relay contact is closed.

• Non-excitation alarm: When the alarm condition, the relay contact is disconnected.

About control

● Heater break alarm (HBA)

The heater disconnection alarm is a current detector (CT) that detects the current through the heater and compares the detected value with the set value of the heater break alarm (HBA). It is the alarm state when the following is true The

① When the control output is ON, the input value of CT is less than the set value of the electric wire break alarm set value

Cause: The heater is broken and the operator is abnormal.

② When the control output is OFF, the input value of CT is less than the set value of the electric wire break alarm set value

Reason: relay contact welding and so on.

● Control loop disconnection alarm (LBA)

The control loop disconnection alarm starts when the control output becomes 100% (or the upper limit of the output limiter) or 0% (or the output limiter lower limit), and the measured value is measured every LBA set time (PV), according to its change to determine whether the control loop is abnormal.

The following is the alarm state:

① When the control output is 100% or more (or the output limiter upper limit)

In the case of positive operation, the decrease in the measured value (PV) is less than the LBA judgment fluctuation (2 ° C) during the LBA setting time.

In the case of reverse action, the increase of the measured value (PV) is less than the LBA judgment variable (2 ° C) during the LBA setting time.

② When the control output is 0% or more (or the output limiter lower limit)

In the case of positive operation, the increase of the measured value (PV) is less than the LBA judgment variable amplitude (2 ° C) during the LBA setting time.

In the case of reverse action, the decrease in the measured value (PV) is less than the LBA judgment variable amplitude (2 ° C) during the LBA setting time.

the reason

Control object abnormality: Heater is broken, power supply is not supplied, wiring error, etc.

Sensor abnormalities: sensor off, short circuit and so on.

Operator Abnormal: relay contact fusion and so on.

Instrument internal anomalies: the instrument within the relay contact fusion and so on.

※ Control circuit disconnection alarm to determine the control loop within the exception, but can not determine the abnormal parts, need to confirm the control system.

· LBA does not feel

Due to external chaos (affected by other heat sources, etc.) Even if the control system is not abnormal, it is possible to become an alarm state (control loop disconnection alarm). In this case, by setting the LBA not felt (LBD), it is possible to set the difference that does not become an alarm state.

About the output

● Output limiter

Limit (upper limit, lower limit) The function of controlling the output range. When the output of the control output is 100%, the output limiter is set to cause the device to adversely affect the output.

● Output rate limiter

And a function of setting a change amount of the control output per unit time.

Used to fear the output of the changes in the device.

● Analog output (conversion output)

(PV) · Set value (SV) · Control output value (MV) · The deviation between the measured value and the set value (DEV) and the opening input value are output in the DC voltage and current state.

Can be used for input of recorder and so on.

For contact input

● Event input (external contact input)

Remote / local switching, switching of the storage area, switching of the steps (SV1 / SV2 switching), switching of the program model, and the like can be performed with signals from the outside.

Those are just my understandings. What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated.

May someone would like to help ?

thanks in advance.