My first job as a controls engineer. How do experience engineers capture I/O's for devices in a system?

I am trying to capture I/O's for devices like valves, pumps with and without vfd, motors with overload...things like that.





I also notice on previous projects from other engineers, the I/O's they had captured for pumps had 2in/out and analog 1in/out. I dont understand really why there would be 2 in/out for a pump. I know that an analog in/out would mean that they have something controlling the motor through a VFD.





So, if anyone can tell me how many I/O's for each devices I had mentioned above and describe the functional of each I/O, I would appreciate it.





Oh, and the system I'm working on is a CIP system (clean in place syst) and what the pump does it pumps water from a supply tank and is controlled by a VFD. Another pump is a return pump with out a VFD. We also have a motor in the system, that is an agitator triggered through a limit switch. So what I'm really looking for are the rule of thumb from experienced engineers when they try to capture I/O's of a system.





if youMy first job as a controls engineer. How do experience engineers capture I/O's for devices in a system?
I’m not sure what you mean by “capture I/O's for devices”


But it sounds like you are trying to write a program to control the CIP.


It sounds like the control you are working with is digital I/O and Analog.





I assume none of the equipment is smart, devicenet, Profibus, etc.





AB Plus freq drives (the Power Flex series are cheaper) require a start and stop command (2 digital outs)


Or you can jumper the 110 control power to the start terminal and it will always be in run mode, open the stop command to stop the drive.





One digital in for a limit switch to tell you if someone turned off the disconnect.





If you want the drive to send back some feed back, at speed, fault, running, etc


You will need 1 digital in for each; at min you would want a fault bit.





To control speed remotely will require an analog out (4-20 ma, 0-10V, etc)


You can send a zero speed command to stop the drive but than the drive will display a zero speed instead of stopped.





I don’t know why you would want to know the speed of the pump on a cleaning system.





I assume you would want to control pressure or flow rate because you are using a VFD drive. So you would need one digital analog in from a pressure transmitter or flow meter.





Knowing your inputted setpoint pressure or flow and the actual pressure or flow from the transmitter you would have a PID loop control the speed of the pump (VFD).





So to control the pump at this point you would need a min of 2 digital outs, 2 digital ins


One analog in and one analog out.





For the agitator, this is probably just a contactor. One digital out to start it. One digital in on the aux contacts to let you know the contactor actually pulled in. And again one digital in to tell you if someone turned off the disconnect. You would be amazed how many time things will not start because some threw the disconnect to work on it and forgot to turn it back on. If this is controled with a float to start and stop, than you will need another digital in.





Agitator one digital out, 3 digital in.





Same would go for the return pump, assuming float control so you don’t pump the tank empty.





Now if you are inquiring about capturing the data from the process, temperature, pressure, flows, ph, ect. That is another ball of wax. Omega has a ton of stuff while would require at least one analog in for each device. We use Allen-Brady PLC’s everything from micro logic to C-logic. For data capture, we use Rs-View to change settings (control varibles) and create the data logs for alarms and keystrokes. Cature data with RSSQL.





The CIP unit you mentioned looks kinda like a PLC controlled Pressure washer, I assume you want to record pressure, temp and cycle times.





I hope this is what you were inquiring, if not, I tried.








Best regards,


TheLightsAreOnButMy first job as a controls engineer. How do experience engineers capture I/O's for devices in a system?
I suggest you contact someone who supplies data collection systems. Ask them for information and price for a system to collect data from your equipment. Omega Engineering provides a wide variety of sensors including thermocouples, encoders, etc. They also have excellent technical support available over the phone. You could also contact companies that supply PLC (Programable Logic Controllers). PLCs take input from digital and a wide variety of analog signals and can transmit digital and anolog signals back out to control devices. Some of the PLC suppliers are Fanuc, Ge, Allen-Bradley.





Experienced engineers either learn it themselves (the hard way) or they learn who to call to get expert advice. If you have a Facilities group or a Maintenance Engineering function, you might find an expert near at hand.





good luck