In this study, we developed a method for calibrating forward scatter meters (FSMs) against transmissometers for measuring visibility under laboratory conditions, and we designed and constructed a novel fog chamber for calibrating FSMs indoors. The fog chamber was used to simulate a controlled visibility environment, and a transmissometer was installed on both ends of the fog chamber as the standard. The developed method involved a comparison of the FSMs and transmissometer in a group of fog events. FSMs were installed on both sides of the optical path between the transmitter and receiver of the transmissometer. The chamber door was closed, and, after creating fog to simulate low-visibility conditions, measurements were collected from the FSMs and transmissometer every minute while the fog dissipated very slowly. The measurement errors of the FSM could then be calculated. To evaluate this method, tests were conducted in the fog chamber, and the results show that the fog chamber could simulate visibility from 10 m to 10 000 m, while the FSMs could only be calibrated below a visibility of 1 500 m due to the baseline of the transmissometer. The fog homogeneity was controlled within 1.2% or less, and the stability was limited to 5% per 30 min. These parameters are reasonably homogeneous and stable for FSM - transmissometer comparison. Three PWD22 FSMs were calibrated using this method, and the calibration uncertainties were estimated to be in the range of 7.8% to 9.2%.

中文翻译：

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一种室内前向散射仪校准方法

在这项研究中，我们开发了一种针对透射仪校准前向散射计 (FSM) 的方法，用于在实验室条件下测量能见度，并且我们设计并构建了一种用于在室内校准 FSM 的新型雾室。雾室用于模拟受控的能见度环境，并且在雾室的两端安装了透射计作为标准。开发的方法涉及在一组雾事件中比较 FSM 和透射仪。FSM 安装在透射仪的发射器和接收器之间的光路两侧。舱门关闭，在产生雾以模拟低能见度条件后，每分钟从 FSM 和透射仪收集测量值，同时雾消散得非常缓慢。然后可以计算 FSM 的测量误差。为了评估这种方法，在雾室中进行了测试，结果表明，雾室可以模拟 10 m 到 10 000 m 的能见度，而 FSM 只能在 1 500 m 能见度以下进行校准，因为基线透射仪的。雾均匀度控制在1.2%以内，稳定性限制在每30分钟5%以内。这些参数对于 FSM - 透射仪比较来说是相当均匀和稳定的。使用这种方法校准了三个 PWD22 FSM，校准不确定度估计在 7.8% 到 9.2% 的范围内。由于透射仪的基线，FSM 只能在 1 500 m 以下能见度下进行校准。雾均匀度控制在1.2%以内，稳定性限制在每30分钟5%以内。这些参数对于 FSM - 透射仪比较来说是相当均匀和稳定的。使用这种方法校准了三个 PWD22 FSM，校准不确定度估计在 7.8% 到 9.2% 的范围内。由于透射仪的基线，FSM 只能在 1 500 m 以下能见度下进行校准。雾均匀度控制在1.2%以内，稳定性限制在每30分钟5%以内。这些参数对于 FSM - 透射仪比较来说是相当均匀和稳定的。使用这种方法校准了三个 PWD22 FSM，校准不确定度估计在 7.8% 到 9.2% 的范围内。