The Subtract function block is used as a mathematical operator and often is used with other Math function blocks. You can send the generated output to a controller or directly to the process.
Application example: Calculate offset
You can use the Subtract function block to determine the difference (error) between a setpoint and a process variable. In this case, the Subtract function block takes the setpoint (IN_1), subtracts the process variable (IN_2), and generates the error signal (OUT). You can send this value to another function block to calculate a cascade input.
Figure: Subtract function block diagram example
