Need info on temperature controller

hello,

I want the information on temperature controller. What is the job of temperature controller in the computer world ?
Can somebody provide me the information on this ?

thanx

Definition -
As the name implies, a temperature controller is an instrument used to control temperature.
A temperature controller accept inputs from temperature sensors or thermometers, and
output a control signal to keep the temperature at the desired level.

In the computer world, a temperature controller is used to control or cool the heat generated
within the processor thereby improving the performance.

Control Techniques - Temperature controllers use several different control techniques:
- Limit control
- Linear control
- Feedforward control
- Proportional, integral and derivative (PID) control
- Fuzzy logic

• Limit control - establishes set points that, when reached, sends a signal to stop or start a process variable.
• Linear control - matches a variable input signal with a correspondingly variable control signal.
• Feedforward control - does not require a sensor and provides direct control-compensation from the reference signal.
• Proportional, integral and derivative (PID) control - requires real-time system feedback. PID control monitors the error between the desired variable value and the actual value, and adjusts the control accordingly.
• Fuzzy logic - is a control technique in which variables can have imprecise values (as in partial truth) rather than a binary status (completely true or completely false).

Temperature controllers that use advanced or non-linear controls such as neural networking, adaptive gain, or emerging algorithms are also available.

Specifications :

Specifications for temperature controllers include
number of inputs, number of outputs, input types, output types,
and number of zones (if applicable).

• The number of inputs is the total number of signals sent to the temperature controller.
• The number of outputs is the sum of all outputs used to control, compensate or correct the process.
• Input types for temperature controllers include direct current (DC) voltage, current loops, analog signals from resistors or potentiometers, frequency inputs, and switch or relay inputs.
• Output types include analog voltage, current loops, switch or relay outputs, and pulses or frequencies.
• Some temperature controllers can also send inputs or receive outputs in serial, parallel, Ethernet or other digital formats which indicate a process variable.