Reply To: PID output percent start at zero

#3769
Anonymous
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Do you have a measured/controlled variable that works in tandem with this PID? In my application we have a feed level PID, feed temperature PID and a evaporator pressure PID. When the level drops during the start up of the equipment the temperature and pressure need to react quicker then the tunning allows, we tune for steady state running. Since the startup only last about 5 minutes we did not want to set up tunning parameters for such a short duration. We use the .BAIS (feed forward) of the PID to speed up the CV response, I calculate the percent error of the process variable vs the set point for the level and pressure loops then use the greater of the two to speed up the temperature loop. The error of the level loop is used to speed up the pressure loop. The .BAIS is a -100 to +100 scaled value that is outside the CV tuning calculation so if it’s a large positive number it has a positive effect on the associated loop if negative then a negative effect ignoring the slow or fast tuning parameters of the PID. I don’t know if you application can benefit from using the .BAIS of the loop but if you do have a measured disruption that affects your application it can be very useful.