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KAHN INSTRUMENTS, INC.
885 Wells Road, Wethersfield, CT 06109
Tel: 860-529-8643; Fax: 860-529-1895
E-mail: [email protected]
www.kahn.com
1.2
Operating Principle
Within the sensor
a Peltier thermoelectric device cools the plated copper mirror. At a
temperature, determined by the moisture content of the sample gas, dew will form on the
mirror surface. This formation of dew causes a reduction in reflected light intensity from
the red LED light source and, at the same time, causes an increase in scattered light
from the mirror surface. This signal change is perceived by a differential optical detection
system, which in turn regulates power to the Peltier via a control circuit. The control loop
maintains the mirror surface exactly at the dewpoint temperature, which is then
accurately measured by an embedded 4-wire platinum resistance thermometer.
The monitoring electronics performs all the control functions for the sensor as well as
measuring and displaying the dewpoint temperature. An automatic balance
compensation (ABC) system is incorporated in the monitor to eliminate the effects of
mirror contamination build-up ensuring continuous accurate operation. If automatic
balance is not required on a specific application the ABC system can be switched off and
the monitor balanced manually when required.
1.3
Calibration
Calibration is performed using precision dewpoint generators and transfer standard
optical hygrometers which have been calibrated directly at the National Institute of
Standards and Technology (
NIST
).
1.4
Manufacturing Quality
Your hygrometer should reach you in perfect working condition. Rigorous procedures at
every stage of production ensure that the materials of construction, manufacturing,
calibration and final test procedures meet the requirements laid down by our Quality
System.
