Monthly Archive: February 2009

Feb
23

What Have I Learned? – Cascade Control (Part 2)

In the February 9 entry on “Unexpected Wireless Benefits” we saw how the positive feedback implementation of the integral mode enabled an enhancement of integral action had benefits that extended beyond wireless devices to any loop with appreciable measurement delay. The positive feedback network sends the controller output or an external reset feedback back through …

Continue reading »

Feb
16

What Have I Learned? – Cascade Control (Part 1)

A cascade control system has a secondary (inner or slave)) loop that gets a remote set point that is the output of a primary (outer or master) loop. The set point of the secondary loop is driven to meet the needs of the primary loop. Most of the benefits stem from the secondary loop correcting …

Continue reading »

Feb
09

What Have I Learned? – Unexpected Wireless Benefits

My original concept of wireless has changed a lot. I always realized that wireless could potentially eliminate most of the installation design and construction costs particularly for inline, pipeline and vessel mounted devices where you don’t have the cost of sensing or sample lines. What is new to me is the additional savings in maintenance …

Continue reading »

Feb
02

What Have I Learned? To Lag or Not to Lag?

The idea of a lag in the control loop just sounds bad but are lags always bad news? The popular consensus is yes. Could a lag could be your best friend despite its bad rep? I was instructed in a graduate class on distillation column modeling and control decades ago that the big problem with …

Continue reading »