Development of a size-of-source effect measurement system for IR thermometers without water-cooling aperture

We have developed a size-of-source effect (SSE) measurement system for infrared (IR) thermometers. The SSE is a key factor for estimating calibration uncertainty, so SSE measurements are essential for calibrating IR thermometers. In general, SSE measurement systems have a water-cooling mechanism to keep their apertures at room temperature. However, such systems are complicated and costly. Here we propose a new SSE measurement system that can keep the aperture at room temperature even though it does not have a water-cooling mechanism. We performed SSE measurements on IR thermometers with the system and obtained satisfactory results. This paper discusses the system, the results, and the SSE measurement uncertainties.