Anti Sweat Heaters, ASH, are commonly used in the retail industry on refrigerator doors to get rid of condensation to build up on the glass.
In many situations the glass is heated constantly to keep it warmer than the dew point. This avoids fog, but it uses a lot of energy and works directly against the compressor that tries to keep the content cool.
ASH controllers will use sensors to only heat the glass when it is really needed, and only heat it just enough to avoid any condensation to occur.
Modern ASH control systems use dew point sensors to monitor the conditions in the air around the refrigerator. A temperature sensor on the glass is then used to adjust the glass temperature to a few degrees above the dew point. In humid climates this can save a lot of energy.