How are field instrument signals transmitted to the field valves?
Thread Content
Dear experts, in the control loop shown below, how is the signal from the on-site temperature transmitter transmitted to the system’s controller, and how is the signal from the controller sent to the on-site valve? Thank you.
The on-site temperature sensing element is connected to the transmitter (or safety barrier), then to the AI card, and further to the controller, where PID calculations are performed; the results are sent to the AO card, from there to the safety barrier, and finally to the valve.
Look at a circuit diagram and you’ll understand.
Thank you for your guidance. From your replies, I understand that in the testing process, the signal is first sent to the transmitter, from there it goes to the safety barrier, then to the AI card, followed by the controller where PID calculations are performed. After that, it reaches the AO card, then back to the safety barrier, and finally to the valve positioner. This understanding should be fine, right, experts?