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Cooled Mirror |
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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.
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