pid with transfer function

[comerford1]

hi i have a simple program that deals with pids and a transfer
function.
basically i want to control a transfer function with a pid and try and
tune
the response. i am having difficulty closing the loop. when i connect
the
output of the transfer function to to process variable it brakes the
wire.
is it hard to close the loop?? i hope the file will open for you. if
it
does vcould you send back an ammended version. this would be great
help.