Output Bias (V5002); Output (V5003) - FACTS Engineering Direct Logic 405 Manual

Output Bias (V5002)

Output Bias or Manual Reset is the result of the integral control action of the PID Temperature
Controller. It is the integral of the error over time and is added to the Output (V5003). Bias
accommodates SetPoint and load changes by eliminating steady state errors. It is sometimes called
automatic reset.
Manual Reset may be used to speed up the automatic reset operation. For example, a large increase in
the SetPoint may cause the Bias to become too large. In this case, the temperature will overshoot the
SetPoint. To prevent this, a predetermined value can be written to the Output Bias location as the
temperature approaches the SetPoint.
Output Bias is also used to provide Feed Forward in anticipation of a process disturbance. For example,
this disturbance could be the addition of colder fluid or a change in flow rate of the fluid being heated. In
both cases the bias could be increased to provide additional heat to stabilize the temperature due to the
disturbance.

Output (V5003)

The Output is the calculated result of the control algorithm based on the current SetPoint, process
temperature, and the control type (ON/OFF or PID). The format of the output is 0.0 to 100.0% when bit 3
of the Mode Word is off or 0 to 4095 when bit 3 of the Mode Word is on. This location is written by the
temperature controller after each loop update. The discrete time proportioned output status is also
written to bit 15 of the Alarm Word.
INSTALLATION AND WIRING 2.15