Sensors, Actuators

Process control sensor types and applications

Taking accurate, reliable measurements of process parameters that matter is the first step to optimizing any control loop. You cannot improve what you do not measure. Process sensors help, including temperature sensors, pressure sensors, level sensors and flow sensors (flow meters).

By Mark T. Hoske, Control Engineering March 4, 2018

Process sensors come in many forms. In addition to the big four: temperature sensors, pressure sensors, level sensors, and flow sensors (more often called flowmeters), process sensors are used in many applications and are designed to take accurate measurements of the process. If the process control system tells actuators move process variables based on inaccurate measurements, things aren’t likely to improve. How can the next generation of process sensing technologies better meet various application requirements for process control applications? 

Use the following process sensors to measure and improve process controls. (Process sensor categories are from the New Products for Engineers Database, which feeds the product sections of Control Engineering and other CFE Media publications.)

Also see the process sensor entries in the 2018 Engineers’ Choice Awards.

Depending on the application, the process sensor can vary widely, based on technology for the process sensing element, process sensor type, size, environment, package, mounting, sensitivity, accuracy, and repeatability. A temperature sensor in a blast furnace, for example, probably would not work on a frozen food processing line. Some applications benefit from non-contact process sensors such as where the sensor avoids contact with the medium to be measured. Other process sensors are right down in the thick (or thin) of things. 

Process sensors are needed to ensure some processes can take place. Outside of a narrow temperature range, the desired result may not occur, hazards may result, quality will suffer, and medications or food can turn into waste.

Multivariable process sensors measure or calculate multiple parameters and often convert into desired units. Please consult vendor documentation for appropriate selection assistance for a particular process sensing application.

Process sensor types and applications

The four most common sensors are temperature sensors, pressure sensors, level sensors, and flow sensors (flowmeters). Other sensors that may be used in process applications follow in alphabetical order:

  • Chemical sensors (many types and sensing elements, including chromatographs)
  • Electrical current sensors
  • Humidity sensors
  • Inductive sensors can be used for level or presence
  • Load sensors (load cells, traditionally thought of as a discrete sensor, can measure tank weight or be used in weigh scales)
  • Machine vision (traditionally thought of as a discrete sensor, but are used on many web-based continuous process sensing applications)
  • Magnetic sensors
  • Micro-electromechanical systems (MEMS), cover many technologies and are perhaps most known for microfluidics
  • Optical sensors
  • pH sensors
  • Power sensors
  • Presence sensors, including photoelectric sensors, proximity sensors
  • Torque sensors (for motors attached to pumps)
  • Vibration sensors (used to monitor process pumps, motors, fans, bearings). 

Mark T. Hoske is content manager, Control Engineering, CFE Media, mhoske@cfemedia.com.

KEYWORDS: Process sensors, temperature sensor, pressure sensor, level sensor, flow sensor

Process sensors measure important process parameters.

Technology, size, and type of process sensors vary widely to fit the application.

CONSIDER THIS

Can smarter process sensors resolve process control, quality, or safety issues?