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	Function Symbol	Individual Symbol (Loop Number)	Description
T	I	C	1012	TIC stands for temperature indicating controller
F	R	C	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.

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	Safety or emergency

Table 3: 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