Chilledmirror

Chilledmirror is a colloquial term used in instrumentation to denote a dew-point or humidity measurement device based on the chilled-mirror principle. In these instruments, a thin reflective surface is cooled by a thermoelectric cooler or a closed-cycle refrigeration module.

As ambient air is directed across the mirror, the mirror temperature is lowered until water vapor in the air starts to condense on the surface. The onset of condensation is detected optically, typically by a camera or photodetector or by changes in reflectivity.

The temperature of the mirror at that moment is read and converted to a dew point value using calibration relationships. The dew point is a measure of humidity independent of air temperature.

Chilledmirror devices are valued for direct, traceable dew-point measurements and fast response times, making them common in laboratories, weather stations, HVAC commissioning, pharmaceutical and semiconductor cleanrooms, and other process-control environments. They require careful maintenance of the optical surface, stable cooling, and protection from drafts or particulates that could affect condensation.

Calibration is achieved against humidity standards, and regular verification ensures long-term accuracy. Variants exist, including portable handheld units and benchtop instruments, with optional data logging and digital interfaces.

The term chilledmirror is sometimes used as a shorthand in technical literature and product literature, though many manufacturers refer to the technique explicitly as chilled-mirror hygrometry or dew-point sensing.