Apparatus and method for diagnostically testing and determining the operating condition of a pneumatically operated valve. A diagnostic controller is connected to a valve actuator assembly so that diaphragm pressure and valve plug movement among other inputs can be sensed while the valve actuator assembly...http://www.google.ca/patents/US5197328?utm_source=gb-gplus-sharePatent US5197328 - Diagnostic apparatus and method for fluid control valves
