How should the accuracy of instruments such as pressure transmitters, temperature transmitters, and level sensors be selected? Are there any guidelines?

When selecting the accuracy of instruments such as pressure transmitters, temperature transmitters, and level gauges, several factors generally need to be considered: 1. Process requirements: The required measurement accuracy should first be determined based on the demands of the process flow. Different processes have varying requirements for the accuracy of instruments. For example, higher precision may be required in some fine chemical processing processes, while less strict precision requirements may apply in some more extensive processing methods. 2. Measurement range: The accuracy of an instrument is related to its measurement range. Typically, the accuracy of a gauge is a percentage of its measurement range. For example, if a pressure transmitter has a measurement range of 0 to 10 bar and an accuracy of ±0.25%, then its precision is ±0.025 bar. 3. Environmental conditions: Environmental factors such as temperature, humidity, and vibration can also affect the performance and accuracy of instruments. 4. Safety and regulatory requirements: In some cases, there may be safety or regulatory requirements that specify exact accuracy standards for instruments, which need to be taken into consideration when making a choice. 5. Economic factors: The cost of the instruments is also an important factor. Generally, the higher the precision of an instrument, the higher its cost. A balanced choice needs to be made based on the budget and the actual requirements for precision. As for whether there are standards, industrial standards around the world may vary. For example, organizations such as the International Electrotechnical Commission (IEC), the American National Standards Institute (ANSI), and the International Organization for Standardization (ISO) may all have relevant standards and specifications. In China, **standards (GB), industry standards, etc., may specify specific requirements for the accuracy of instruments in certain applications. Users should select instruments with the appropriate accuracy based on the standards of their specific industry and local regulations. In practical applications, design specifications, corporate standards are usually referred to, or advice is sought from experienced instrument engineers, to ensure that the selected instruments meet the project requirements. .

GB/T 50770-2013 Code for Design of Safety Instrumented Systems in Petrochemical Industries; GB/T 50892-2013 Code for Design of Instrumentation and Control Systems in Oil and Gas Fields and Pipeline Projects; HG/T 20507-2014 Specifications for the Selection and Design of Automation Instruments; SH/T 3005-2016 Specifications for the Selection and Design of Automation Instruments in Petrochemical Industries. Check these standards, or look for similar ones

When the user has no specific requirements regarding the instruments, standard practices from various industries are followed, but it is necessary to confirm this with the user； The user has a separate specification sheet; just follow the requirements outlined in that document.