GB/T 2625-1981 in English

《GB/T 2625-1981过程检测和控制流程图用图形符号和文字代号》由TC124（全国工业过程测量控制和自动化标准化技术委员会）归口，主管部门为中国机械工业联合会。
本标准适用于化工、石油、冶金、电力、轻工、纺织、建材和其他工业，旨在为过程检测和控制流程图所用的仪表装置规定统一的表示方法。本标准所规定的图形符号和文字代号还可供其他设计文件和技术文件之需。

1. Introduction

1.1 This standard is applicable to chemical industry, petroleum industry, metallurgical industry, electricity industry, light industry, textile industry, building materials industry and other industries. It aims at specifying unified representation method for the instrument devices used in process detection and control flow chart.
The symbols and letter codes specified in this standard may also be used in other design and technical documents.
1.2 The mark of instrument device is composed of symbols and letter codes.
1.3 All departments may put forward supplementary provisions under the condition that requirements of this standard are not violated.

2. Definitions

For the purposes of this standard, the following definitions apply.
2.1 Process
It refers to any operation or a series of operations that can change energy status, composition, dimension or other characteristics defined by the data available.
2.2 Function
It refers to the purpose and actions achieved by instruments.
2.3 Loop
It refers to the combination of one or more relevant instruments used for measuring and (or) controlling process variables.
2.4 Ballon
It refers to the circular symbol used to indicate instrument or instrument mark.
2.5 Point of measurement
It refers to the point at which process variable may be measured.
2.6 Test point
It refers to the test joint to which instruments are not permanently connected and it is used for connecting instruments temporarily, intermittently or in future.
2.7 Detecting element, sensor, primary element
It refers to the element responding to the value of measured variable directly and converting measured variable to the form suitable for measurement.
2.8 Transmitter
It refers to the instrument which receives measured variable with the help of detecting element and coverts the measured variable to standard output signal. Transmitter may or may not include detecting elements.

1. Introduction
2. Definitions
3. Symbols
4 Letter Codes
Appendix 1
Appendix 2