PID Function in PL7-Pro V3.4

[fergal 0]

Hello All, I am a student in Cork, Ireland. My years project involves controlling the water level of two interacting tanks using a Modicon TSX Premium. Im using the PID function in PL7-pro V3.4. I believe i have programmed all the parameters of the function block correctly and both the analog input counts (set-point and process variable) are being read correctly by the PLC. The problem is that there is no output coming from the PID block to the assigned analog output (it is staying at zero). The output address on the module ios in perfect working order. I have tried a number of different ideas over the past week but to no avail. If anybody has any ideas on what i could be missing or even an example program it would be greatly appreciated. Thanks in advance... Yours Sincerely Fergal

[rajsiyer 7]

Hi Kid, I've seen this thing happen very often in my own work and those of my engineers:-). The most common cause of this is that you have perhaps not made the parameters Outmax & Outmin (%mwi + 6 & 7of the PID block) to 10,000 and zero respectively. Another reason it may not work is because you have written the PID instruction in a FAST task whereas you've assigned the Analog inputs and outputs to a MAST task. The Dumbest reason may perhaps be that you have not put the PLC in RUN mode! Regards, Best wishes for your success Raj S. Iyer