Isa Intrumentation Codes

Reference data and engineering information about isa intrumentation codes for process control applications.

isaintrumentationcodes

Overview

Engineering reference data for Isa Intrumentation Codes in process control.

Key Formulas

PID Controller

$u(t) = K_p e(t) + K_i \int e(t)dt + K_d \frac{de}{dt}$

Proportional-Integral-Derivative control.

Transfer Function

$G(s) = \frac{K}{\tau s + 1}$

First-order system.

Variables

Symbol	Description	Unit
$K_p$	Proportional gain	—
$K_i$	Integral gain	1/s
$K_d$	Derivative gain	s
$\tau$	Time constant	s

ISA Letter Code Reference Tables

The ANSI/ISA S5.1 standard defines a systematic approach for labeling instruments in P&IDs using a combination of letters. Below are consolidated reference tables.

53 rows

ISA Instrument Letter Codes (ANSI/ISA S5.1)
Category	Letter Code	Description
First Letter (Measured Variable)	A	Analysis
First Letter (Measured Variable)	B	Burner, combustion
First Letter (Measured Variable)	E	Voltage
First Letter (Measured Variable)	F	Flow rate
First Letter (Measured Variable)	I	Current (electrical)
First Letter (Measured Variable)	K	Time, time schedule
First Letter (Measured Variable)	L	Level
First Letter (Measured Variable)	P	Pressure, vacuum
First Letter (Measured Variable)	Q	Quantity
First Letter (Measured Variable)	R	Radiation
First Letter (Measured Variable)	S	Speed, frequency
First Letter (Measured Variable)	T	Temperature
First Letter (Measured Variable)	U	Multivariable
First Letter (Measured Variable)	V	Vibration, mechanical analysis
First Letter (Measured Variable)	W	Weight, force
First Letter (Measured Variable)	X	Unclassified
First Letter (Measured Variable)	Y	Event, state or presence
First Letter (Measured Variable)	Z	Position, dimension
First Letter (Modifier)	D	Differential
First Letter (Modifier)	F	Ration (fraction)
First Letter (Modifier)	J	Scan
First Letter (Modifier)	K	Time rate of change
First Letter (Modifier)	M	Momentary
First Letter (Modifier)	Q	Integrate, totalizer
First Letter (Modifier)	S	Safety
First Letter (Modifier)	X	X-axis
First Letter (Modifier)	Y	Y-axis
First Letter (Modifier)	Z	Z-axis
Second Letter (Readout/Passive)	A	Alarm
Second Letter (Readout/Passive)	E	Sensor (primary element)
Second Letter (Readout/Passive)	G	Glass, viewing device
Second Letter (Readout/Passive)	I	Indication
Second Letter (Readout/Passive)	L	Light
Second Letter (Readout/Passive)	O	Orifice, restriction
Second Letter (Readout/Passive)	P	Point (test connection)
Second Letter (Readout/Passive)	R	Record
Second Letter (Readout/Passive)	U	Multifunction
Second Letter (Readout/Passive)	W	Well
Second Letter (Readout/Passive)	X	Unclassified
Second Letter (Output Function)	C	Control
Second Letter (Output Function)	K	Control Station
Second Letter (Output Function)	S	Switch
Second Letter (Output Function)	T	Transmit
Second Letter (Output Function)	U	Multifunction
Second Letter (Output Function)	V	Valve, damper, louver
Second Letter (Output Function)	X	Unclassified
Second Letter (Output Function)	Y	Relay, compute, convert
Second Letter (Output Function)	Z	Driver, actuator
Second Letter (Modifier Function)	H	High
Second Letter (Modifier Function)	L	Low
Second Letter (Modifier Function)	M	Middle, intermediate
Second Letter (Modifier Function)	U	Multifunction
Second Letter (Modifier Function)	X	Unclassified

Source: ANSI/ISA S5.1-1984 (R 1992)

Common P&ID Code Examples

The letter combination is followed by a unique identification number (e.g., 001). The table below shows standard patterns and their meanings.

4 rows

Examples of Instrument Identification Codes
Code Pattern	Meaning	Example
FI	Flow Indicating	FI 001
TT	Temperature Transmitter	TT 001
FV	Flow Valve	FV 001
ZSH	Position Switch High Level	ZSH 001

Source: ANSI/ISA S5.1-1984 (R 1992)

References

Original Source

Source: engineeringtoolbox.com