Positioners
A positioner is an instrument used to increase the accuracy and speed of an actuator in response to a control signal. It acts as a controller, using feedback from the actuator to ensure that the actuator's position precisely matches the setpoint signal from a main control system. Positioners are most commonly used with pneumatic actuators to overcome issues like friction and hysteresis.
How a Positioner Works
A positioner operates based on a feedback loop principle. It takes two inputs:
A command signal: This is the desired position sent from a control system (like a PLC or DCS). This signal is typically a 4-20 mA current or a 3-15 psi pneumatic signal.
A feedback signal: This is the actual position of the actuator's stem or shaft, which the positioner measures.
The positioner then compares these two signals. If there's a difference, it adjusts the air pressure going to the actuator's diaphragm or piston. It will either increase the pressure to move the actuator toward the desired position or decrease it to allow the actuator to move back. This process continues until the feedback signal matches the command signal, at which point the actuator is held in the correct position.
A positioner is an instrument used to increase the accuracy and speed of an actuator in response to a control signal. It acts as a controller, using feedback from the actuator to ensure that the actuator's position precisely matches the setpoint signal from a main control system. Positioners are most commonly used with pneumatic actuators to overcome issues like friction and hysteresis.
How a Positioner Works
A positioner operates based on a feedback loop principle. It takes two inputs:
A command signal: This is the desired position sent from a control system (like a PLC or DCS). This signal is typically a 4-20 mA current or a 3-15 psi pneumatic signal.
A feedback signal: This is the actual position of the actuator's stem or shaft, which the positioner measures.
The positioner then compares these two signals. If there's a difference, it adjusts the air pressure going to the actuator's diaphragm or piston. It will either increase the pressure to move the actuator toward the desired position or decrease it to allow the actuator to move back. This process continues until the feedback signal matches the command signal, at which point the actuator is held in the correct position.