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YOKOGAWA

Yokogawa Electric Corporation

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June, 2007

Instrumentation Symbol Standards


This document explains how to read instrumentation symbols that frequently appear in instrumentation drawings. For further details, please read the relevant standards documentations.


Instrumentation symbol standards are established by ISO 3511/1-1977*¹ and JIS8204-1983*². For instrumentation equipment (1-loop) that carries out a series of functions, ISO/JIS defines 1 character symbol (an alphanumeric using capital letters), or a graphic symbol that expresses the same concepts in a drawing.


*¹: ISO 3511/1-1977 Process measurement control functions and instrumentation – Symbolic representation – Part1: Basic requirements
*²: JIS8204-1983 instrumentation symbols


The following shows examples of character and graphical symbols used for instrumentation.

Examples of Instrumentation Character Symbols

As shown in tables 1 and 2, character symbols consist of variable symbols, function symbols (and combinations thereof), and individual symbols (loop numbers), in that order.

Variable Symbol Function Symbol Individual Symbol (Loop Number) Description
T I 1012 TIC stands for temperature indicating controller
F R 1013 FRC stands for flow recording controller
P T 1014 PT stands for pressure transmitter

Examples of Instrumentation Graphical Symbols

Graphical symbols consist of the symbols in table 3 and combinations thereof.

Diaphram valve, Motorized valve

Common Instrumentation Character and Graphical Symbols


Table 1: Variable symbols

Symbol Variable Symbol Variable
D Density or specific gravity P Pressure or vacuum
E Electrical quantity S Speed, revolutions, or frequency
F Flow T Temperature
L Level V Viscosity
M Moisture or humidity W Weight or force


Table 2: Function symbols

Symbol Measurement Equipment
Format or Function
Symbol Measurement Equipment
Format or Function
A Alarm R Recording
C Correction S Sequence control
E Detection T Transfer or conversion
I Indication Y Computation
Q Integration Z Sagety or emergency

Table 3: Common graphical instrumentation symbols

Common graphical instrumentation symbols

Further reading:
1. ISO 3511/1-1977 Process measurement control functions and instrumentation – Symbolic representation – Part1: Basic requirements
2. JIS8204-1983 instrumentation symbols