SAMA Diagrams - I

SAMA is an acronym standing for Scientific Apparatus Makers Association, referring to a unique
form of diagram used primary in the power generation industry to document control strategies.
These diagrams focus on the flow of information within a control system rather than on the process
piping or instrument interconnections (wires, tubes, etc.). The general flow of a SAMA diagram is
top-to-bottom, with the process sensing instrument (transmitter) located at the top and the final
control element (valve or variable-speed motor) located at the bottom. No attempt is made to
arrange symbols in a SAMA diagram to correlate with actual equipment layout: these diagrams are
all about the algorithms used to make control decisions, and nothing more.

A sample SAMA diagram appears here, showing a flow transmitter (FT) sending a process
variable signal to a PID controller, which then sends a manipulated variable signal to a flow control
valve (FCV):