Process Instrumentation 4: Actuators

Actuators

• Actuators are devices used to produce action or motion in response to an input signal, which can be electrical, air, or fluids.
• Actuator outputs can be positioned or rate-based, resulting in linear displacement or velocity.
• Actuation can range from a few microns to a few meters.

Types of Actuators

• Hydraulic actuator: uses hydraulic fluid to amplify the control command signal.
• Pneumatic actuator: uses compressed air as the driving force.
• Mechanical actuator:
• Electrical actuators:
  • Electric motors
  • DC servomotors
  • AC motors
  • Stepper motors
  • Solenoids

Solenoid

• A solenoid is a coil wound into a tightly packed helix that produces a magnetic field when an electric current is passed through it.
• Classified as a type of linear, translational actuator.
• Applications of solenoids include:
  • Electromagnets
  • Inductors
  • Antennas
  • Valves
  • Medical devices
  • Locking systems
  • Industrial use
  • Automotive systems

Hydraulic Actuator

• Hydraulic systems are used to control and transmit power.
• A pump driven by a prime mover (electric motor) creates a flow of fluid.
• Types of hydraulic actuators:
  • Linear actuator (Hydraulic cylinder):
    • Provides motion in a straight line.
    • Linear displacement depends on stroke length.
    • Commonly referred to as cylinders, rams (single-acting cylinders), or jacks.
  • Rotary actuators (Hydraulic motors):
    • Produces continuous rotational motion.
    • Pump shaft is rotated to generate flow.
    • A motor shaft is caused to rotate by fluid being forced into the driving chambers.
  • Semi-rotary actuators:
    • Produces non-continuous rotational motion.
    • Limited to less than one revolution.

Learn about actuators, devices used to produce action or motion, including their types, functions, and applications in process instrumentation. Understand the input and output signals, and how they can be used to control motion and position.