Method and apparatus for deterministically obtaining process controller parameter measurements when a process is operating online

摘要

A diagnostic test unit for deterministically measuring one or more parameters, such as dead band, dead time, response time, gain, or overshoot, of a process control device that is connected in a process control loop during operation of a process includes a switch controller, a signal generator, a switch, a response accumulator mechanism, and an analyzer mechanism. The switch controller monitors a process signal during operation of the process to determine whether the process signal is substantially stable. In the event that the process signal is substantially stable, the switch replaces a control signal with a diagnostic test signal generated by the signal generator. The response accumulator is in communication with the process control loop to obtain an indication of the response of the process control device to the diagnostic test signal. The analyzer unit then determines the device parameter from the test signal and the response indication.