I am aware of standard Naming conventions from ISA S5.1 and that AIT or the "A" is generally used as the tag for an analyser.
Recently, I have come across people using Q for this and saying it's because it is a Quality instrument, as in monitoring the "quality" of something.
Has anyone else come across this?
I am putting Tags into a SCADA for Turbidity, Aluminium monitoring and a Cytometer for bacterial growth.
These would all carry the AIT tag and then the unique site MIMS number that is used by the company.

 

Retired from a plant in Texas built in the late 70s that was a copy of a plant in the UK. Analyzers were designated as Q-xxxx as yours. That being said Towers were all E-xxxx, vessels were F-xxxx, heat exchangers were C-xxxx and rotating equipment was J-xxxx. The Q for quality made sense but the rest I never did figure out.

 

Retired from a plant in Texas built in the late 70s that was a copy of a plant in the UK. Analyzers were designated as Q-xxxx as yours. That being said Towers were all E-xxxx, vessels were F-xxxx, heat exchangers were C-xxxx and rotating equipment was J-xxxx. The Q for quality made sense but the rest I never did figure out.

Sounds about right, nothing seems to change here... Everything has some form of legacy from how it was done in the past....

 

You are correct to use A for the measurements mentioned as it falls under analysers/analysis, it is the measurement or initiating variable under measurement or control.

Under ISA 5.1 the use of Q as a first letter is prescribed as Quantity not Quality.

If you are encountering people referring it to a quality then we need to treat them gently and educate them on the ways of ISA 5.1 as they have a gap in their knowledge that needs to be filled to prevent future misinterpretation. It is easy for the less experienced to make a mistake, I have encountered the letter R being used for density measurements, it was assigned R by the drafting team, because the density gauge had a radiation source.

If you have found this use then location/facility is not to standard and its likely is a local user variation or a user mistake coming from a miss read of the spelling of the words quantity and quality. Either case needs to be corrected if the location/facility is hard aligned to ISA standards. The ISA assigned letters are not allowed to be re-assigned, only letters allocated to user definition can be made to suit local requirements. And thise user assigned letters have to be defined and recorded in normal engineering design documents.

Good luck