If industrial control systems are the brains of a plant, then sensors are its eyes and ears. Simply put, without sensors there would be nothing for SCADA, DCS, or PLCs to respond to. That’s why increasingly intelligent or “smart” sensors packing more onboard processing power, the ability to monitor new variables, and digital communication capabilities are playing such an important role in helping plant operators and enterprise level planners alike to see better and respond to problems with more finesse.
In the past, sensors were largely relegated to the status of mere on-off switches. When inputs such as temperature, flow, or proximity pass a certain threshold, an analog sensor sends out a current or voltage signal to set a simple control loop into action. For instance, fans could speed up or slow down, control valves might change position, or bumpers on a conveyor may be actuated.
Today’s smart sensors, however, are different in a number of ways, says Manikandan Nambiar, vice president of product management for Plantweb and reliability solutions at Emerson Automation Solutions. Most importantly, many contain micro electro-mechanical systems (MEMS) along with onboard microcontrollers, which allow them to collect and process more information in real-time.
The use of this technology in modern sensors reflects two major trends at play: The first is “sensor fusion,” or the ability for a single sensor to monitor multiple input types, leading not only to more granular insights, but cost efficiencies as well. In essence, more data can be attained without needing to invest in multiple devices. Secondly, the capacity to track how inputs are changing over time may allow maintenance personnel and others to move from engaging in a merely reactive approach—that is, responding to a problem when an on-off switch is tripped—to truly understanding the root cause of a failure and moving to prevent it from happening again.
“There’s a lot of different ways to define a smart sensor, depending on the type you’re talking about; but in my mind, where the smarts really come in is with these MEMS along with the microcontrollers,” says Christopher Koch, senior application engineer for connected devices and solutions at Bosch Rexroth. “When you add these components, you can have sensors that have accelerometers, gyroscopes, and magnetometers all combined into one; or environmental sensors that have temperature, pressure, and humidity all together. Then you have the ability to communicate that data into upstream analytics sites. That’s really what a smart sensing device is.”