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Types of temperature Control Instrument and what’s their features?

Types of temperature control instrument:

1.       Two switches ON/OFF action

As the picture shows on the left, when the actual temperature is lower than the set

value, the heater is energized. When the actual temperature is higher than the set value, the heater is not energized. The way to maintain certain temperature according to the heater power supply’s on or off is called two switches style or ON/OFF.

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2.       Three switches style

When the actual temperature is lower than the lower-limit and upper limit set value, the two heaters is energized together. When the actual temperature is higher than the lower-limit set value, one of the heater’s power is cut off, the other one is still working. When the actual temperature is higher than the upper-limit set value, the other heater’s power is also cut off. The way to maintain certain temperature according to the heater power supply’s on, half-on or off is called three switches style.

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3.       Time proportional action(p)

After the actual temperature enters the proportional band generated by the set value, the proportional action that operation amount(control output amount) acts on deviation value at a certain period and interruption is called time proportional action.

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4.       Integral action (I)

OFFSET appears when the proportional action works, and combine the integral action with the proportional action. As the time goes by, OFFSET will be eliminated, and make the actual temperature accord with the set value.

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5.       Differential action(D)

The integral action and proportional action can correct the control result, but in any case, it is too slow. Differential action can supplement its shortcomings, and correct with the operation amount of tilt differential co-efficient caused by the deviation, we call this correct action as differential action.

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6.       Continuous PID action

PID is a combination of proportional action, integral action and differential action, and it has good control effect on control objects with different working hours. Because continuous PID action is not easy to oscillate, with the integral action against foreign chaos, and it can react quickly.

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7.       Continuous proportional action(p)

It is similar to time proportional action, but continuous proportional action in the proportional band, the action which operation amount acts on deviation is continuously change.

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8.       Continuous PID action

The working process of continuous PID action is similar to the Intermittent PID action, but control accuracy is higher than the latter.

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Advantages and disadvantages:

Nos

Types

Advantages

Disadvantages

1

Two switches ON/OFF action

Easy to control,no OFFSET Overshot and oscillation.

2

Three switches style

Small overshot, no OFFSET Overshot and oscillation.

3

Time proportional action(p)

Small overshot and oscillation Cost much time before it’s stable, OFFSET occurs.

4

Integral action (I)

Eliminate OFFSET Cost much time before it is more stable because of proportional action.

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Differential action(D)

React quickly Cannot separately control

(combine with proportional action).

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Continuous PID action

Better Control characteristics Need to set PID parameters, oscillation still occurs.

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Continuous proportional action(p)

Better Control characteristics OFFSET will happen after it’s stable.

8

Continuous PID action

Best Control characteristics Need to set PID parameter.

 

 


Post time: May-22-2019
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