The Bias/Gain (BG) function block provides adjustable gain capability by computing an output value from a bias setpoint, an input, and a gain value. The block supports output tracking. The Bias/Gain function block is designed to be used as an element in parallel control paths, such as a plant master driving multiple boiler masters.
In Automatic (Auto) mode, the output is computed automatically and the bias setpoint can be adjusted manually. In Manual (Man) mode, the output can be set manually.
To provide bumpless transfer and anti-reset windup, you connect the BKCAL_OUT parameter to a master controller and the BKCAL_IN parameter to a slave controller. When bumpless transfer is not achieved completely by BKCAL_OUT and BKCAL_IN, an internal bias is computed and applied at transfer time. This bias is ramped over a specified time period.
You connect the tracking inputs (TRK_IN_D and TRK_VAL) for externally controlled output tracking.
IN_1 is the input value and status.
BKCAL_IN is the analog input value and status from another block's BKCAL_OUT output that is used for backward output tracking.
TRK_IN_D is the Boolean input used to initiate the external tracking function.
TRK_VAL is the input value OUT is set to in Local Override (LO) mode (while TRK_IN_D is true).
OUT is the biased analog output value and status.
BKCAL_OUT is the output value connected to the BKCAL_IN input of another block to prevent reset windup and to provide bumpless transfer to closed loop control.
The following diagram shows the internal components of the Bias/Gain function block:
