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4.6
Microscope
It is possible in certain circumstances that between 0 and -20 °C. super-cooled water
may form on the mirror surface instead of ice. The theory for this phenomenon is quite
complex but the effect is that, for a sample of fixed water vapor concentration, the
controlled mirror temperature is affected by as much as 2 °C. Super-cooled water
formation leads to dewpoint values lower than would be seen if ice crystals were formed.
If you require further advice on this matter please contact Kahn Instruments' Technical
Sales Department.
The microscope allows direct viewing of condensate on the mirror surface providing
visual evidence that ice crystals have formed in the critical region between 0 and -20 °C
dewpoint.
The microscope is fitted into the sensor cover by replacing the black screw threaded plug
with the microscope. Ensure the instrument is measuring a dewpoint then screw the
microscope into the sensor cover until sharp focus of the mirror surface is achieved. As a
guide to the focal point, the microscope should only have about four to five threads
showing when it is screwed in. Fine adjustment will be necessary to obtain sharp focus.
When the instrument is controlling at a dewpoint condensation is seen on the mirror as
small bright red specks on a dark background. Liquid water is seen as rounded droplets
and ice as sharp-edged crystals.
KAHN INSTRUMENTS, INC.
885 Wells Road, Wethersfield, CT 06109
Tel: 860-529-8643; Fax: 860-529-1895
E-mail: info@kahn.com
www.kahn.com
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