ISO 18787:2017确立了在0至1的测量范围内测定人类消费食品和动物饲料的水分活度（aw）的方法的基本原则和要求。 测量原理基于露点测量或基于电解质的电导率或聚合物的介电常数变化的确定。 该方法不适用于储存在其冰点以下（相当于产品中出现冰晶的温度）的产品，也不适用于对应于脂肪包水乳液的产品，也不适用于晶体产品如糖、盐或矿物质。 对于含有挥发性化合物（例如醇）的产品，可能需要特定的设备适应来应用该方法。 进行的实验室间研究的结果见附件B。

ISO 18787:2017 establishes basic principles and specifies requirements for the methods of determining water activity (a_w) of food products for human consumption and animal feed within a measurement range of 0 to 1. The measurement principles are based on the dew-point measurement or on the determination of the change in electrical conductivity of an electrolyte or in the permittivity of a polymer. The method does not apply to products stored below their freezing point (equivalent to the temperature at which ice crystals appear in the product), neither to products corresponding to a water-in-fat emulsion, nor to crystal products such as sugars, salt or minerals. For products containing volatile compounds, such as alcohols, specific equipment adaptations may be necessary to apply the method. The results of the interlaboratory studies that were carried out are given in Annex B.