ISA takes position on wireless network symbology

Thanks to Tom McAvinew and Al Iverson of the ISA Standards and Practices Board for responding to my challenge to come up with how to deal with industrial wireless networks using the ISA standards for documentation and design drafting for instrumentation systems.

The following was posted to the Controls mailing list maintained by ISA this morning:


September 18, 2008 

With the advent of wireless instrumentation becoming a viable and secure means communication in the industrial sector, there are increasing numbers of inquiries regarding the need to have symbols specific to this technology and to have these new symbols included in ISA 5.1.

This standard is currently being revised and will soon be forwarded to the S&P Board of Directors for consideration of approval. This statement will attempt address those inquiries. 

From the earliest ISA standard on the subject of symbols and identification, RP5.1, Instrumentation Flow Plan Symbols first published in 1949, through several revisions including the current ANSI/ISA5.1-1984 (Reaffirmed 1992), Instrumentation Symbols and Identification, it is clear that the intent has always been to establish a system whereby devices are identified and symbolized by function rather than form.  

Thus we can have device depictions and alpha character designations that are identical whether they are pneumatic or electronic, analog or digital-based with the distinguishing representation being the signal transmission symbol. As for state-of-the-art wireless systems, the fundamental characteristic is obviously the signal communication means, i.e., radio transmission.

Upon examination of the existing ISA 5.1 standard, there is a broken sine wave symbol (see below) in Section 6.2 (8) defined as “Electromagnetic or Sonic Signal (Not Guided)” with a footnote including radio waves in the definition. In addition, the current draft of the ISA 5.1 revision includes a “lightning bolt” symbol (see below) which has been in use by some practitioners in one form or another in pre-“wireless” radio applications.

In other words, by the time the ISA 5.1 revision is presented to the S&P Board of Directors, there will be two symbols available to represent the primary unique function of wireless instrumentation devices in Automation systems.  

It is therefore the consensus of the S&P leadership responsible for symbols and identification that sufficient means exist for the representation of wireless instrumentation, and that beyond the addition of the defacto lightning bolt symbol, no other symbols are required. 


Sine Wave Symbol             




Lightning Bolt Symbol  

Tom McAvinew, Vice-President, ISA Standards and Practices Department

Ian Verhappen, Managing Director, ISA Standards and Practices Board

Al Iverson, Chairman, ISA 5, Documentation Standards Committee

Jim Carew, Chairman, ISA 5.1, Instrumentation and Symbols Committee