Control device for a pneumatically operated actuator

A control device for a pneumatically operated actuator for actuating a process valve in order to control a material flow in a pipeline, said control device comprising:

• a communications interface for receiving an electrical setpoint value, and varying at its output, the pressure of a pneumatic fluid as a function of a control deviation,
• wherein the received electrical setpoint value is suitable as a process parameter, and the control device including a second interface connected via a communications channel to an actual-value encoder, the second interface is for receiving an electrical signal output by the actual-value encoder corresponding to an actual value of the same process parameter, and for receiving diagnostic data from the actual-value encoder
• wherein the actual-value encoder evaluates the actual value of the process parameter to diagnose a condition of at least one of the process valve and the control device, and
• wherein the actual-value encoder is a differential pressure transducer which measures pressure and differential pressure and internally evaluates raw data to perform a diagnostic function of at least one of the process valve and the control device.