Yes — every ISA-5.1 tag is read positionally, not as a word. The letters split into a first letter and succeeding letters.
The FIRST letter is the measured or initiating variable: F=flow, T=temperature, P=pressure, L=level, A=analysis, W=weight/force, S=speed, etc. The SUCCEEDING letters are, in order: an optional modifier, then the readout/passive function, then the output/active function, then another modifier. Common succeeding letters: I=indicate, C=control, T=transmit, R=record, S=switch, V=valve/damper, Y=relay/compute, Q=totalize, E=sensor/element, and H/L/HH/LL as high/low modifiers.
So: FT-101 = Flow Transmitter, loop 101. TIC-201 = Temperature Indicating Controller, loop 201. FCV-104 = Flow Control Valve, loop 104. LIC-102 = Level Indicating Controller. PSHH-330 = Pressure Switch, High-High — a trip-level pressure switch.
Read it left to right as "variable, then what it does" and it decodes cleanly every time. The letter table and worked examples are in /standards/isa-5-1.html and the bubble/instrument conventions are in /learn/instrument-symbols.html
The FIRST letter is the measured or initiating variable: F=flow, T=temperature, P=pressure, L=level, A=analysis, W=weight/force, S=speed, etc. The SUCCEEDING letters are, in order: an optional modifier, then the readout/passive function, then the output/active function, then another modifier. Common succeeding letters: I=indicate, C=control, T=transmit, R=record, S=switch, V=valve/damper, Y=relay/compute, Q=totalize, E=sensor/element, and H/L/HH/LL as high/low modifiers.
So: FT-101 = Flow Transmitter, loop 101. TIC-201 = Temperature Indicating Controller, loop 201. FCV-104 = Flow Control Valve, loop 104. LIC-102 = Level Indicating Controller. PSHH-330 = Pressure Switch, High-High — a trip-level pressure switch.
Read it left to right as "variable, then what it does" and it decodes cleanly every time. The letter table and worked examples are in /standards/isa-5-1.html and the bubble/instrument conventions are in /learn/instrument-symbols.html