For the Right Process Data in the Control Room, Start with Reliable and Accurate Instrumentation

 There are many stages of information exchange that need to happen between a process and the control room in order to have an accurate process measurement. A good process measurement starts with good measurement instrumentation, and the importance of having reliable instrumentation is discussed in the article “Getting Stronger Process Readings”, published in Control Engineering. Although the article uses the example of pressure measurement, the same idea applies to broader measurement instrumentation: each element in the communication path must work correctly for successful process control and monitoring.  To use an excerpt that details this path nicely:

  • “The process fluid must have a path to reach the sensor
  • The pressure sensor must be deflected in a measurable way in proportion to the fluid pressure against atmosphere
  • An electrical element must convert the deflection into an analog signal
  • The transmitter must clean up the raw signal, scale it, and transmit it using a prescribed format, either analog or digital
  • Wires, or perhaps radio, must carry the signal to the input/output (I/O) card of the automation system
  • The automation system must convert the signal into appropriate engineering units for display and use the data in whatever equations it is performing for the larger control effort”

Interference anywhere in this chain can distort or inhibit the process measurement. However, modern technologies such as advanced diagnostics and WirelessHART are helping to ensure measurement accuracy. For example, the Plugged Impulse Line diagnostic can detect when a transmitter is no longer seeing true process values due to an obstruction in the line.  Wireless communication protocol can eliminate many of the problems with traditional wiring, but plants that haven’t made the transition to wireless can still take advantage of information provided by the Loop Integrity diagnostic to monitor for proper functioning. Even with these additional technologies, no matter how robust and sophisticated the communication pathway is, measurement data is only going to be as good as the source that captures it – the instrumentation.

You can read more here. What steps do you take to make sure you’re reliably getting the process data you need?