Tagnaming conventions for modifiers

Anybody got any thoughts on tagnaming, especially the modifiers. For example setpoint is SP, process variable is PV, which is great in the analog world but I want to use a similar arrangement for motors, limits and other digital stuff.
If I use FWD for forward status, what to use for forward command?
Ideally I would like to keep it to 3 or 4 letters

Thanks in advance
Geoff

we use several, not everyting is going to suit everybody though !

al_ = alarm
ct_ = control
uf_ = user field
av_ = actual value
sp_ = setpoint
st_ = status

hello Geoff;

For valves and motors we also distionguish between commands and feedback signals:

-cmd_ST_Mxxx: command from PLC to start a motor
-fdb_ST_Mxxx: feedback from motor reporting started (running) status
-cmd_OP_Vxxx: command from PLC to open a valve
-fdb_OP_Vxxx: feedback from valve reporting open status

Again, as pointed out by tragic,it might not suite everyone, but we like to maintain similarities between tagnames in the PLC and in the SCADA. Reduces debugging a great deal.
Hope this helps,
Daniel Chartier

Daniel

How do you distinguish between a STarted -fdb_ST_Mxxx and STopped -fdb_ST_Mxxx motor?

What? You mean you don't have stopped sensor on every motor? You'll be telling me next you don't have an ON indicator attached to every lamp!

Ken

With RSLogix500, I gave up on the tagname ("Symbol") years ago when it was limited to 10 characters. I just use the Description (100 characters in five lines of 20 each) and turn off the Symbol display in the editor. (These days, the Symbol is up to 20 characters but that's still not enough, especially if the first few have to be something like "STN_01_....) So my ladder looks something like:

STN 01
Raise
Vacuum Port
Seal Lift Cyl

STN 01
Vacuum Port
Seal Lift Cyl
Raised

With the ease of Excel import, I do all my tag maintenance in Excel and just pull in updated lists as needed. You can copy the actuator or sensor base description and then change the ending to things like "Up Verified" "Failed to go Up Fault Timer" "Failed to go Up Fault" "Failed to go Up Fault Count" etc. Since these are all different files, after you create the base lists for command and feedback you just copy them to new file numbers, change the endings, and in a few hours I have hundreds of tags. The logic in the PLC is then identical for each actuator on the machine- just change the bit numbers- and the terminology is too which makes it easier for me to debug later.

I do the same thing for the HMI, and I have some Excel spreadsheets that concatenate the five 20-char fields into one that is sucked in for the HMI "description."

The only downside is that I usually have to create fake tags in the HMI (usually something like "N7_000" to "N7_255") for each bit or word of each data file that I want in the HMI, since you can't easily see the description when tying a tag to a screen object. And then, since "B03_08_12" is not all that descriptive, you have to go to the HMI tag editor and look at the imported description. But so far I've been able to live with that since it makes it a lot easier to read and maintain the ladder, which is harder than the HMI.

We developed a list for use when we were working with AutoMate PLC's and documentation options were limited.

Thanks guys

The variety of responses shows just how much easier the process control guys have it. Tagnames seem to have caught us in the plc world by surprise, with many just making their own standards or else as PaulT stated just giving up and using desciptors

Thanks again, your ideas will help me develop my 'standard'
Geoff

I try and stick to the ISA conventions. I posted a quick reference sheet for it here some time ago. http://www.plctalk.net/qanda/showpost.php?p=158326&postcount=9

In a CLX I often use a ISATag_ShortDescription format for naming PLC tags. Using UDTs really helps for extensions, eg UDTTAGNAME.PIDE.PV, etc.

Most of my work has been designing controls for the industrial and automotive. Lately I’ve started doing some process design work. Below is a scenario that gives me problems:



In the process world and using ISA standards, what would the tagname be for a PLC output that is wired to an interposing relay that controls a large solenoid that opens a valve.



Relay tagname = XD801 ??

Solenoid tagname = VD719A ??

PLC tagname = ?????



As a controls guy I want the PLC output tag to have the relay tag’s name in it because that is the first place I’d electrically check when troubleshooting (after the PLC output itself). Our main customer wants it to be the valve tagname. The problem with this is that their prints are hard to find or missing you’d never know the relay was there unless you started tracing wires.



In the industrial world the PLC descriptor might be:

2104CR

Open Drain Valve

3325SV



2104CR = page # and line # for where to find the relay (pg. 21 line 04 relay)

3325SV = page # and line # for where to find the relay (pg. 33 line 25 solenoid valve)