Speed of Response for Mass Flow Meters, Alicat Scientific, Inc.

Technical FAQ

Alicat instruments' inherently fast response speed is a result of the method of measurement used. Changes in differential pressure across a fixed point are taken almost instantaneously. Click here to view an Alicat MC series flow controller's response time.

In thermal devices, the elapsed time necessary to heat or cool a thermocouple or RTD is the limiting factor in response time.
In an effort to overcome this limitation, many thermal manufacturers attempt to anticipate response based on the rate of change (projections based on the slope of a line). This can lead to over and undershooting in process control. Actual response time of a typical thermal mass flow meter is between 0.5 to 3 seconds once this slope estimate is removed.

Increased speed yields faster processes and better results. The faster a controller can respond to changes the more stable and more reliable a system becomes. It is easier to think of an accelerator and brake system on a car. The faster the accelerator and brake systems make changes the easier it is to drive the car. If you apply gas or hit the brake you want the car to begin moving, or stop, as quickly as possible. Imagine if you had to wait for the car to respond when braking...especially if you had to stop quickly!

Many processes work in much the same way. The slower the controls are to respond, the harder it is to work with the system. Although it may not seem to be as critical to change gas flow as it is to stop a car, in some cases the cost of incorrect gas flow at critical times could be a lot more expensive than a simple fender bender. Learn more about Alicat's MC series line of mass flow controllers.

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