Automated sorption balances are widely used for characterizing the interaction of water vapor with hygroscopic materials. These instruments provide an efficient way to collect sorption isotherm data and kinetic data. A typical method for defining equilibrium after a step change in relative humidity (RH) is using a particular threshold value for the rate of change in mass with time. Recent studies indicate that commonly used threshold values yield substantial errors and that further measurements are needed at extended hold times as a basis to assess the accuracy of abbreviated equilibration criteria. However, the mass measurement accuracy at extended times depends on the operational stability of the instrument. Published data on the stability of automated sorption balances are rare. An interlaboratory study was undertaken to investigate equilibration criteria for automated sorption balances. This paper focuses on the mass, temperature, and RH stability and includes data from 25 laboratories throughout the world. An initial target for instrument mass stability was met on the first attempt in many cases, but several instruments were found to have unexpectedly large instabilities. The sources of these instabilities were investigated and greatly reduced. This paper highlights the importance of verifying operational mass stability of automated sorption balances, gives a method to perform stability checks, and provides guidance on identifying and correcting common sources of mass instability.

自动吸附天平广泛用于表征水蒸气与吸湿材料的相互作用。这些仪器提供了收集吸附等温线数据和动力学数据的有效方法。在相对湿度 (RH) 阶跃变化后定义平衡的典型方法是使用质量随时间变化率的特定阈值。最近的研究表明，常用的阈值会产生很大的误差，需要在延长的保持时间内进行进一步的测量，作为评估简化平衡标准准确性的基础。然而，长时间的质量测量精度取决于仪器的运行稳定性。关于自动吸附天平稳定性的已发表数据很少。进行了一项实验室间研究来调查自动吸附天平的平衡标准。本文重点关注质量、温度和相对湿度稳定性，包含来自全球 25 个实验室的数据。在许多情况下，第一次尝试就达到了仪器质量稳定性的初始目标，但发现一些仪器具有出乎意料的大不稳定性。对这些不稳定因素的根源进行了调查并大大减少了。本文强调了验证自动吸附天平操作质量稳定性的重要性，给出了执行稳定性检查的方法，并为识别和纠正质量不稳定的常见来源提供了指导。