RMPS and RLIM on a ControlLogix: Ramping a Setpoint Instead of Stepping It A sequence step writes 75.0 into the speed reference of a PowerFlex on a packing line that was sitting at 20.0, and the drive comes back with an overcurrent on acceleration about 400 ms later. Nothing in the controller did anything wrong. … Read more
A 1756-OF8 is a 0…20 mA module, and at full counts it puts out 21.29 mA. Nothing in the hardware knows that the positioner on the end of the wire wants 4 mA for closed and 20 mA for open, or that 0 mA on an air-to-open valve is the same as closed and 21 … Read more
Read process gain, dead time and time constant off one bump test, then enter them in the units PIDE actually wants instead of the ones the PID wants.
How the BPCS, the SIS and the package PLC split the work on a batch reactor, with a cause and effect matrix, cascade temperature control and IS barriers.
PLC vs DCS programming compared by an engineer who works on both: tags and rungs against loops and blocks, redundancy, alarms, batch and real cost.
Scale the analog signals, pick PID or PIDE, put the loop in a periodic task, then tune from a bump test. Siemens PID_Compact covered as well.
A function block routine that verified fine last week now has a question mark on four blocks and will not download. Or worse, it downloads, runs, and one value on the HMI is always one scan behind the others. Nobody moved a block. Somebody added a wire. Execution order in FBD has nothing to do … Read more