The Optica Hygrometer offers precision dew point measurement. Precisely controlled by GE's chilled mirror sensing technology - providing NIST traceable humidity,temperature and pressure measurement anywhere via the worldwide intranet. The Optica Chilled Mirror Hygrometer measures dew point temperature by regulating the temperature of a polished metal mirror by the use of optical feedback such that a constant mass of dew or frost is maintained. The temperature of the mirror is measured with a precise PRTD and is by definition equal to the dew or frost point.