What is a Controller?


A controller, or “process” controller, is an electronic device used in a closed loop system to read an input value from a measuring device and provide a controlled output to achieve and maintain a desired setpoint value. See the diagram example below. 



The controlled variable is measured by a suitable sensor and converted to a signal acceptable to the controller. The controller compares the measured value to the desired value (setpoint) and actuates the control device as needed. The control device alters the manipulated variable by changing the appropriate properties to achieve and maintain accurate and stable levels of control behavior at or near the setpoint.



Gems 3100 Series - pressure transducer measures 275 PSI pressure in a pressurized chamber and sends a 4-20 mA scaling linear signal to a West 6100 Plus Series - controller.



The process controller converts that signal to read PSI, and the setpoint is adjusted to 250 PSI. The controller provides an output to a valve actuator. When actuated, the valve opens to allow pressure to vent to atmosphere until 250 PSI is measured by the pressure transducer. This process is repeated (looped) with continuous monitoring and feedback to accurately hold the desired 250 PSI setpoint. 


A process controller can be used for a specific task. Because of this, process controllers in comparison to other controllers, like a programmable logic controller (PLC), are: 

  • More cost efficient  
  • Easier to set up 
  • Can be portable or mobile 
  • Includes built-in display 
  • Is usually more accurate 
  • Includes features, outputs, and control options directly related to the process 

Controllers can have additional outputs and options to perform auxiliary functions: 

  • Alarms 
  • Retransmit 
  • Communications 
  • Integral Power Supply 
  • Remote Setpoint 
  • Digital Inputs 
  • And more... 

Gems Sensors & Controls and West Control Solutions are happy to offer a wide range of controllers to help with your process control needs. See more  HERE.