May 2005

In this issue

	Classes and seminars
	About us
	Trick for this month
	To contact us

See our previous issues :
http://www.topcontrol.com/techinfo/news.php

Classes & seminars

Milwaukee, WI, June 6-10
EX-501-3 - Detailed Loop Analysis with ExperTune and
EX-502-3 - ExperTune Advanced Tools
You can attend both classes in 1 week from June 6 to 10.

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SAIL Amsterdam 2005

From 17 to 22 August 2005, Amsterdam will be the home port to one of the biggest maritime event in the world for the seventh time, SAIL Amsterdam 2005. For six days, Amsterdam will be a vibrant exhibition of historic ships and nautical heritage. During SAIL Amsterdam 2005, about 20 Tall Ships are expected in Amsterdam harbour, together with 500 historic sailing and motorboats. More information on www.sail.nl

Michel Ruel from Top Control will present the class:
ME-200-3 - Analytical methods for troubleshooting and Control loop tuning, August 22-24

The first 5 inscriptions will receive free tickets for an exclusive Sail Amsterdam 2005 boat night tour on the 21 of August on a sailboat. Highlight will be the special firework show at 11.30 PM.

About us

See our 2005 calendar, Classes & Seminars :

See at : http://www.topcontrol.com/training/tcalendar.php

Trick for this month : Noise or Disturbance?

When a disturbance occurs, will PID controller succeed to reject it?
First, we need to determine which periods can be rejected.

Loop tuned to reject disturbances:

• t_settling ~ 10 · t_d

                 (where t_d is process dead time)

Loop tuned to reach SP at a certain speed:

• t_settling ~ 4 ·

                  (where is the time to reach 63% of SP change; is usually ~ 3 ·_process)

When a disturbance happens faster than settling time, it is noise and PID controller will not reject this disturbance. In such a case, a filter is added on PV to ensure the controller will not fight this quick disturbance and apply this noise to its output, causing useless valve movement and wear.

Hence :

• if period < t_settling, filter will mask noise;
• if period > t_settling, PID will reject disturbance.

The filter time constant is :

_F ~ t_d /5        or        _F ~ t_settling /50        or        _F ~ /10

Watch filters with too long time constant!

To contact us

Comments, suggestions and requests are welcomed. Please e-mail us at: info@topcontrol.com

You are welcomed to visit our web site :http://www.topcontrol.com

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