A couple of weeks ago I started a poll on device numbering methods, here are the results. Responses came from comments on this site and five different Linked In forums.
Method 1: Labeling the device based on the I/O point it is connected to: 5 votes
Method 2: Labeling the device based on where it appears in the electrical schematics (i.e. line/page number): 12 votes
Method 3: Labeling the device based on mechanical or physical layout (i.e. P&ID or similar): 7 votes
Responses were broken down much as I thought they would be. Method one voters were mostly OEMs and method three voters seemed to come from a process control background or from Europe (IEC standards). Method two seems to be the default for manufacturing plants and machine builders, at least in this country.
Though only 24 people actually had an opinion, several more commented on the subject without expressing a preference. Quite a few more hit “like” on the topic without making a comment.
As I mentioned, I have had to use all three on different projects depending on customer standards and preferences.
Thanks for all of the comments and responses!