Micromote optical precision tube sensors are designed to detect free-floating air bubbles in transparent liquids. These free-floating air bubbles have dimensions smaller than their tube's inner diameter. The sensor's ability to detect these bubbles results from a uniform illumination of the tube's liquid column. This uniform illumination is created by a concentrated arrangement of multiple light beams, each with an individual uniform intensity distribution, surrounding the tube. When a small air bubble enters the sensing field, it induces a significant signal jump on the sensor's receiver elements. This signal jump enables reliable detection of tiny air bubbles, including microbubbles.