Cooled Mirror Michell's Cooled Mirror Dew- Point Hygrometers are precision instruments for critical measurement and control applications. The fundamental nature of this method means that Cooled Mirror instruments can be used as either extremely reliable and stable field instruments or as laboratory reference standards for the calibration of other devices. Michell's Cooled Mirror Sensors are fundamental in their method of operation. A miniature polished stainless steel mirror is cooled by a solid plate Peltier thermoelectric heat pump until it reaches the dewpoint of the gas under test. When this temperature has been reached, condensation will begin to form on the mirror surface. An electro-optical loop detects that condensation is forming, by a reduction in the intensity of light reflected from the mirror surface and through the control electronics of the cooled mirror instrument. This modulates the cooling power applied to the Peltier. The mirror surface is then controlled in an equilibrium state whereby evaporation and condensation are occurring at the same rate. In this condition the temperature of the mirror (measured by a platinum resistance thermometer) is equal to the dew point temperature of the gas. Fast responding chilled mirror technology The new design uses a thin, fast responding hybrid mirror that is highly resistant to corrosion from acids and other gas contaminants, outlasting any traditional cooled mirror sensor design.