The refresh rate is measured with Herz or Hz, which is named after the German physicist Heinrich Hertz. Hz is a unit of frequency, which tells you the number of how many times per second one period of an image is cycled. For example, if the refresh rate of a thermal imaging device is 50 Hz means that in one second the cycle repeats 50 times or in other words 50 Hz is 50 frames per second (50 fps). The higher the refresh rate the more frames will appear on display each second, the smoother the rendering and less blurry will the image appear. A standard image refresh rate is 30 Hz or 30 frames per second but turns out to be less efficient when you or the target is moving fast. 50 Hz provides a much smoother image in movement. The lower the frequency of the image, the lower the cost. But devices with 9 Hz refresh rate are not recommended if the inspections are constantly moving objects at a long distance. 50 Hz devices are preferred because they provide a real-time image with no delay.