Asi and noise immunity


Thread Starter

willy o.

Actuator Sensor Interface
ASi V1.0
ASi V2.1
Safety ASi
What provides the noise immunity for any of these ASi versions, particularly when the flat cable is used for the ASi busway ?
Also send articles and/or whitepapers and relevant presentations which approach noise immunities in greater details than the standard

James Ingraham

I'm not really an AS-i expert, but I think I've seen Gary Frigyes of Pepperl & Fuchs posting, and he IS an AS-i expert, so hopefully he'll chime in here.

From what little I know, however, it works like this; AS-i isn't noise immune at all! In fact, the idea is to let there be as much noise on the line as you want. But the trick is that the noise will affect both the Positive and Negative lines of the voltage. Then, when the AS-i device looks at the signal, it subtracts the two, leaving a perfectly clean signal because the noise on the two legs cancel each other out. So no matter how much noise you've got going on it won't affect the AS-i signal This is beautiful because now you're not worried about seperating voltages or shielding the cables or even twisting the wires. The other systems try to BLOCK the noise. AS-i just ignores it!

Please, anyone, feel free to correct me.

Sage Automation, Inc.

Garrett Place


The noise immunity on an AS-i system is derived from a number of different things (too much detail to go into here). I suggest looking at
the and sights for some basic details. There is also a book out there, "AS-interface; The Actuator-Sensor
Interface for Automation" By Kriesel and Madelung that will give you much more detail on the subject. This book can be ordered off of either of the above web sights or you can drop me an e-mail, [email protected], and I will send you a copy.

Good luck.

Donald Pittendrigh

HI All

Do not believe all you hear and read about ASI and its reputed noise immunity. In Kriesel and Madelung there are some few lines that recommend that the ASI cables are routed separately from power cables, the point is underemphasised, I have two different clients who have both had severe problems because of a) running the signal wires and bus cables in trunking in MCC cubicles, and b) running the ASI signal wires and bus cables in close proximity to VSD motors and or power cables where vector control is employed. ASI is very definitley not immune to interference and normal guidelines for installation of serial communications cables should be followed. The signal wires can also cause noise to be introduced to the system, I quite frankly consider the ASI equipment that I have worked with to be Heath Robinson and of debatable quality for controlling garage doors.

One of the above clients will never let ASI on his plant again and the other didnt have the budget to get rid of it so ended up with all sorts of interposing relays to try and keep the noise out of the system. I will personally never touch it again myself and would recommend that you dont even waste your money buying the book. Pity as it has some nice convenience features.