VTdrive Why do we need temperature controllers0 pages

Why do we need temperature controllers?
Temperature controllers are needed in any situation requiring a given temperature be kept stable. This can
be in a situation where an object is required to be heated, cooled or both and to remain at the target
temperature (setpoint), regardless of the changing environment around it. There are two fundamental types
of temperature control; open loop and closed loop control. Open loop is the most basic form and applies
continuous heating/cooling with no regard for the actual temperature output. It is analogous to the internal
heating system in a car. On a
cold day, you may need to turn the heat on to full to warm the car to 75°. However, during warmer weather,
the same setting would leave the inside of the car much warmer than the desired 75°.

Open loop control
block diagram
Closed loop control is far more sophisticated than open loop. In a closed loop application, the output
temperature is constantly measured and adjusted to maintain a constant output at the desired temperature.
Closed loop control is always conscious of the output signal and will feed this back into the control process.
Closed loop control is analogous to a car with internal climate control. If you set the car temperature to
75°, the climate control will automatically adjust the heating (during cold days) or cooling (during warm
days) as required to maintain the target temperature of 75°.

Closed loop control
block diagram
Introduction to Temperature Controllers
A temperature controller is a device used to hold a desired temperature at a specified value.
The simplest example of a temperature controller is a common thermostat found in homes. For instance,
a hot water heater uses a thermostat to control the temperature of the water and maintain it at a certain
commanded temperature. Temperature controllers are also used in ovens. When a temperature is set for
an oven, a controller monitors the actual temperature inside of the oven. If it falls below the set
temperature, it sends a signal to activate the heater to raise the temperature back to the setpoint.
Thermostats are also used in refrigerators. So if the temperature gets too high, a controller initiates an
action to bring the temperature down.
Common Controller Applications