Blogs

What are Good Signal Filtering Tips?

Noise in control loops can wear out valves and get amplified by proportional and derivative action. The filter should reduce noise to an acceptable level without appreciably slowing down the loop. I have enlisted the help of key industry experts to provide their guidance.

What Are the Merits of Options to avoid a Kick on a Setpoint Change Tips?

The PID structures with proportional on error cause a step change in the PID output for a large setpoint change. For structures with derivative on error there is also a sharp bump almost looking like a spike unless you zoom in.

Is it better to have a Controller with More or Less Knobs Tips?

What are the relative merits of different PID structures, a setpoint (SP) filter, and analog output (AO) setpoint rate (velocity) limits? Should I seek a general solution I can use all the time and each knob fits a particular purpose, or a controller with fewer knobs that does exactly what...

How do you Effectively Use Anti-Reset Windup Options Tips?

Anti-reset windup (ARW) protection is a standard feature of industrial PID controllers. In some DCS, ARW limits are adjustable besides output limits.  The ARW limits may not be at their best values. ARW default values may not match up with output limits as output scale and engineering units change.

Checklist for Success Tips

This last checklist may help you get the most out of your career and your life.  Our accomplishments and our humanity are tightly related. The checklist is a summary of an understanding gained of an attitude and philosophy that has helped me be a better engineer and person.  The checklist...

Checklist for Bioreactor Control Tips

Contrary to common conceptions, bioreactors have more sophisticated analysis and control and with the advent of at-line analyzers more extensive opportunities than chemical reactors. The specialty chemical industry can get a preview of the future from the biopharmaceutical industry.

Checklist for Liquid Pressure and Flow Control Tips

Nearly every process input is a flow, whether directly via a material input flow or indirectly via an energy input (e.g., utility flow). Good flow control is important for achieving the desired material and energy balance and stoichiometric ratio for reaction rates.

Checklist for Gas Pressure Control Tips

Nearly all of the deadtime in pressure loops comes from the automation system. For gas pressure there is a process time constant or integrating process gain that becomes slower as the volume increases and the throughput decreases.

Checklist for Compressor Surge Control Tips

Compressor surge is the fastest gas dynamic phenomena. A precipitous drop in flow occurs in 0.05 seconds and subsequent flow reversals occur every 1 to 2 seconds. The speed of response requirements for control valves, measurements, and controllers are extraordinary.

Checklist for Level Control Tips

The maximum level controller gain for stability is one or two orders of magnitude higher than expected. The main limit to how high you can go in controller gain is often measurement noise and control objective.