IEC 62828-4:2020 establishes specific procedures for testing level transmitters used in measuring and control systems for industrial process and machinery control systems. For general test procedures, reference is to be made to IEC 62828-1:2017, applicable to all types of transmitters. Throughout this document, the term "industrial transmitters" covers all types of transmitters used in measuring and control systems for industrial processes and for machinery. The requirements of this document are applicable to all level measurement principles. Detailed description of transmitters is given for two main principles for improved clarity.