ISA instrument codes

I've got a weird situation where I need to provide a tagname for some PLC inputs for several equipment "start request" points coming from another PLC (PLC-X sending a hardwired request to PLC-Y to start a piece of equipment controlled by PLC-Y).



Customer naming conventions require I use ISA standard instrument codes for any hard input or output signals, but I've never encountered a hardwired "request" before. Typically, I'd use an HSH or an HSL suffix for start/stop commands going directly to the equipment, but not for a request. Any ideas? Granted it's sort of subjective, but I was curious what other folks have used.

I generally use something that starts with 'X' (unclassified). You have a lot of choices for the 2nd and 3rd letters. I've seen XS, XI, XY, XA used before. Nothing wrong with XN (unclassified, users choice) for a tag with no specific meaning at all. Just pick something and be consistent in how you use them.

If all else fails, ask your customer if you can talk to those in engineering or maintenance for assistance. Tell him you are wanting to see what they are used to and want to get it right the first time and avoid any misunderstanding.

james

If all else fails, ask your customer if you can talk to those in engineering or maintenance for assistance. Tell him you are wanting to see what they are used to and want to get it right the first time and avoid any misunderstanding.

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+1 to that.

Get the customer to buy in to your interpretation of their spec.

ISA 51.1 define tag names. Not knowing your system I guess I'd call it YS, but as suggested above go tot he customer.