I am an Intern at an automation Company and required to know almost evrything about PID but i'm kind of stuck at Bumpless Transfer. I googled and referred to alot of manuals but couldn't get through any proper explanation.

can somebody please explain me the same and also the modes i.e. auto to manual bumpless transfer and vice versa with suitable examples

 

In bumpless transfer from manual to automatic or vice versa, some of the realtime settings and process values are transferred from the old mode to the new with the intent of avoiding any abrupt changes in control or process from the mode change.

For example, assume you've been in manual mode for a while at a certain output percentage and your PV has stabilized at some value.

If you switch from manual to automatic mode, you might preset the auto mode SP to the manual mode PV, and take the manual mode percent output and load it into the auto mode bias term. Since SP-PV == 0 and both are stable, P and D terms are 0 at the moment immediately after you change to auto, and the process will remain at that point till something changes; you make a setpoint change or the load changes, and in that case, the process and the control will respond smoothly as they would to the same event had you always been in auto mode.

Changing from auto to manual, you might take the entire output, P+I+D, and move it to the manual output percentage. Similar to the above case, nothing extreme will happen directly attributable to the mode change.

 

thank you steve, i was helpful..............