Valve controllers, which are often referred to as valve positioners, are the smart field devices that receive commands and control the valve actuators to open or close a valve, or to move the disc or ball into the desired position for optimal flow rates and characteristics. Positioners are used for pneumatically operated valves (ie. valves assemblies with pneumatic actuators) that depend on a positioner to take an input signal and convert it into the desired valve travel.
Pneumatic and electropneumatic positioners are the most common analog valve positioners. They convert a pneumatic or electric signal into the air pressure required to move the valve to the correct position. Digital valve controllers function in a similar manner but include sensors and intelligence to improve the control performance and optimal operation with diagnostics. These smart devices can utilize numerous different communications options including HART 6 or 7, Foundation Fieldbus, or Profibus PA. Bluetooth technology can also be utilized for wireless connectivity.