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1. A measurement point (primary point) refers to the point in a detection system or control system that is in direct contact with the process medium. Such as the pressure sampling points in pressure detection systems, and the installation points of thermocouples and thermal resistors in temperature detection systems. A point can be on the process pipeline or on the process equipment. 2. Primary components (source components) generally refer to the instrument components installed at the primary points, such as pressure tapping fittings in pressure monitoring systems and thermometer protrusions in temperature measurement systems. 3. Primary valves (pressure tapping valves) refer to valves installed on primary components, such as those in the pressure measurement system connected to the pressure tapping adapters, and valves connected to the inlet and outlet pipes of the positive and negative pressure chambers of the orifice plate. 4. Primary elements (sensors) refer to components that are installed on-site and in contact with the process medium, such as thermocouples and thermal resistors. 5. Field instruments are a type of instrument used in the field; they are those that are installed on-site and come into direct contact with the process medium, such as Bourdon tube pressure gauges, bimetallic thermometers, differential pressure transmitters, etc. 6. Initial calibration (individual calibration) refers to the verification carried out before the installation of instruments. In accordance with the requirements of the \"Code for Construction and Acceptance of Industrial Automation Instrumentation Projects\" (GBJ—86), in principle, each instrument must undergo initial calibration. The focus of calibration is to check the indication error and drift of the instruments, as well as to adjust errors in the instrument’s proportional gain, integration time, differentiation time, control point deviation, and balance. An instrument that meets the requirements specified in the design or product manual can be installed only once, in order to ensure the quality of the subsequent calibration. 7. Secondary instruments refer to the general term for various types of instruments whose indicated values are not directly related to the process medium. The input signal of secondary instruments is usually a standard signal converted by a transmitter. There are generally three types of standard signals received by secondary instruments: pneumatic signals; Type II electric unit combination instrument signals; and Type HI electric unit combination instrument signals. 8. Field instruments refer to the general term for instruments installed on-site, including all primary instruments as well as secondary instruments installed at the site. 9. Secondary calibration (secondary alignment, system calibration) refers to the inspection of the entire detection circuit or automatic control system after the instruments have been installed on-site, and once the piping and wiring in the control room are completed and have passed verification; it is also a comprehensive calibration performed before the instruments are put into formal use. Its verification method typically involves adding a signal during the testing phase, and then carefully checking whether each instrument in the system is operating within the allowable error range. If it exceeds the allowable error range and no cause can be found, all the instruments making up the system must be recalibrated. 10. Instrument processing parts refer to the general term for all metal and plastic mechanically processed parts used in instrument installation, and they play a special role in such installations. 11. A flowchart with control points is a diagram that uses symbols from process monitoring and control system design to describe the automation aspects of a production process. It details the installation locations of the instruments; it is an important drawing for determining the primary measurement points, a comprehensive reflection of the automation scheme and the level of automation, as well as a basis for automation design. It serves as a reference for construction, installation, and operational activities. 12. The common instrumentation and control graphic symbols are in accordance with the **industry standard HG20505—92 \"Alphabetic Codes and Graphic Symbols for Process Detection and Control Systems\"**, with reference to standard GB2625—81; the common graphic and alphabetic codes used in chemical process automation are as follows. The graphic symbol ① measurement point (including the sensing element) is the starting point of the connecting lead that leads from the process equipment or pipeline symbol to the instrument circle; it generally has no specific graphic symbol. ②If the measurement point is located within the equipment, and it is necessary to indicate its position within the process equipment, a small circle symbol with a diameter of 2 mm or a dashed line can be added at the starting point of the lead. ③The connection line graphic symbol represents the lead connecting the instrument circle to the process measurement point; the symbol for general instrument signal lines and power lines is a thin solid line. When it is necessary to indicate the energy category, the corresponding abbreviation can be used above the energy line symbol. For example, AS-014 is an air source with a pressure of 0.14 MPa, while ES-24DC is a DC power supply with 24 V. ④When a solid thin line is used for general instrument signal wires and this may cause confusion, a diagonal dash can be added to the solid thin line as a symbol for general signal wires (the diagonal dash forms a 45° angle with the solid thin line).