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2024年3月26日发(作者：傅里叶变换推导)
1 Purpose
The purpose of this standard is to establish a uniform means of designating instruments and
instrumentation systems used for measurement and control. To this end, a designation system
that includes symbols and an identification code is presented.
2 Scope
2.1 General
2.1.1 The procedural needs of various users are different. The standard recognizes these needs,
when they are consistent with the objectives of the standard, by providing alternative symbolism
methods. A number of examples are provided for adding information or simplifying the symbolism,
as desired.
2.1.2 Process equipment symbols are not part of this standard, but are included only to illustrate
applications of instrumentation symbols.
2.2 Application to industries
2.2.1 The standard is suitable for use in the chemical, petroleum, power generation, air condition-
ing, metal refining, and numerous other, process industries.
2.2.2 Certain fields, such as astronomy, navigation, and medicine, use very specialized instruments
that are different from the conventional industrial process instruments. No specific effort was made
to have the standard meet the requirements of those fields. However, it is expected that the
standard will be flexible enough to meet many of the needs of special fields.
2.3 Application to work activities
2.3.1 The standard is suitable for use whenever any reference to an instrument or to a control
system function is required for the purposes of symbolization and identification. Such references
may be required for the following uses, as well as others:
•Design sketches
•Teaching examples
•Technical papers, literature, and discussions
•Instrumentation system diagrams, loop diagrams, logic diagrams
•Functional descriptions
•Flow diagrams: Process, Mechanical, Engineering, Systems, Piping (Process) and
Instrumentation
•Construction drawings
•Specifications, purchase orders, manifests, and other lists
ISA-5.1-1984 (R 1992)9
•Identification (tagging) of instruments and control functions
•Installation, operating and maintenance instructions, drawings, and records
2.3.2 The standard is intended to provide sufficient information to enable anyone reviewing any
document depicting process measurement and control (who has a reasonable amount of process
knowledge) to understand the means of measurement and control of the process. The detailed
knowledge of a specialist in instrumentation is not a prerequisite to this understanding.
2.4 Application to classes of instrumentation and to instrument functions
The symbolism and identification methods provided in this standard are applicable to all classes
of process measurement and control instrumentation. They can be used not only to describe
discrete instruments and their functions, but also to describe the analogous functions of systems
which are variously termed "shared display," "shared control," "distributed control," and
"computer control."
2.5 Extent of functional identification
The standard provides for the identification and symbolization of the key functions of an
instrument. Additional details of the instrument are better described in a suitable specification,
data sheet, or other document intended for those requiring such details.
2.6 Extent of loop identification
The standard covers the identification of an instrument and all other instruments or control
functions associated with it in a loop. The user is free to apply additional identification — by
serial number, unit number, area number, plant number, or by other means.
3 Definitions
For the purpose of understanding this standard, the following definitions apply. For a more
complete treatment, see ISA-51.1 and the ISA-75 series of standards. Terms italicized in a
definition are also defined in this section.
Accessible: A term applied to a device or function that can be used or be seen by an operator
for the purpose of performing control actions, e.g., set point changes, auto-manual transfer, or
on-off actions.
Alarm: A device or function that signals the existence of an abnormal condition by means of an
audible or visible discrete change, or both, intended to attract attention.
It is not recommended that the term alarm switch or alarm be used to designate a device whose
operation is simply to close or open a circuit that may or may not be used for normal or abnormal
interlock, start-up, shutdown, actuation of a pilot light or an alarm device, or the like. The first
device is properly designated as a level switch, a flow switch, etc., because "switching" is what
the device does. The device may be designated as an alarm only if the device itself contains the
alarm function. [See also Table 1, note (13).]
Assignable: A term applied to a feature permitting the channeling (or directing) of a signal from
one device to another without the need for switching, patching, or changes in wiring.
Auto-manual station: Synonym for control station.
10ISA-5.1-1984 (R 1992)
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