本欧洲标准的第3部分规定了用于满足高精度体积转换装置的计量和技术要求的流量计算机（FC）的构造，性能，安全性和一致性的要求和测试。 它们用于确定根据EN 437的第一和第二族的燃料气体体积。 为了本欧洲标准的目的，只考虑使用符合ISO 17089 1的超声波仪表或符合EN 12261标准的燃气轮机的流量计算机。 为了本欧洲标准的目的，流量计算机仅考虑E2和M1类别的分类。 FC配有外部独立的压力和温度传感器，可单独批准。 有关压力和温度传感器的规定见附件B和C. EN 12405中的能源计算器的要求和测试2

Part 3 of this European Standard specifies the requirements and tests for the construction, performance, safety and conformity of flow computers (FCs) used to meet the metrological and technical requirements of a high accuracy volume conversion device. They are used to determine volume of fuel gases, including those of the first and second families according to EN 437. For the purpose of this European Standard, only flow computers that are intended to operate with ultrasonic meters according to ISO 17089 1 or gas turbine meters conforming to EN 12261 are considered. For the purpose of this European Standard only classification classes E2 and M1 are considered for the flow computer calculator. FCs are equipped with external separate transducers for pressure and temperature which may be approved separately. The provisions concerning pressure and temperature transducers are given in Annex B and C. Requirements and tests are given for energy calculator in EN 12405 2.