All About Temperature Controllers

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Temperature Controller
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All About Temperature Controllers

• A temperature controller popularly known as
  Humidity controller is an instrument used to
  control temperatures, mainly without any
  extensive operator involvement in the
  process. In a temperature control system, a
  controller will accept a temperature sensor
  such as a RTD or thermocouple as input
  and do comparison between the actual
  temperature and the desired temperature, or
  set point. It then provides an output to a
  control element.

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• The controller is usually forms just one
  part of a temperature control system.
  Therefore for selecting a proper
  temperature controller for the system, the
  entire system should be analyzed.
• Types of Controllers and How Do They Work?
• There are basically three types of controllers
• On/Off Control
• Proportional Control
• PID Control
• On/Off Control
• It is the simplest form of a temperature control
  device. The output from the device is
  either on or off, without any middle state.
  Only when the temperature crosses the set
  point, the on/off controller will switch the
  output. Since the temperature crosses the
  set point to change the output state, the
  process temperature will go on cycling
  continually. It goes from below set point to
  above, and back below. For such systems, an
  on-off differential is usually added to
  controller operations.

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• Proportional Control
• They are designed to eliminate the cycling
  associated with on-off control. A
  proportional temperature controller works by
  decreasing the average power supplied to
  the heater as the temperature approaches
  the set point. This effectively slows down
  the heater so that it will not overshoot
  the set point, but will approach the set
  point and maintain a stable temperature.
• PID Control
• The third of controller provides
  proportional with integral and derivative
  control, or PID. The PID controller combines
  proportional control with two additional
  adjustments (the integral and derivative
  control), which helps the unit to
  automatically compensate for changes in the
  system. It provides the most accurate and
  stable control of all the three control
  types.

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• It is recommended in systems where the
  load changes often and the controller is
  expected to automatically compensate for it.
• Points to be kept in mind while selecting a
  Temperature Controller
• Type of input sensor and temperature range
• Type of output required
• Control algorithm needed
• Number and type of outputs

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