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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
6.
MAINTENANCE
6.1
Cleaning the Optical System
The Kahn Series 4000
Integrale
is a precision optical dewpoint hygrometer, which uses a
four component optical system to detect condensation of water from a gas sample. This
system comprises a light emitting diode (LED), two photo-detectors and a mirror surface.
The LED and scattered light photo-detector are isolated from the gas stream by light
guides so only the ends of the light guides inside the measurement chamber and the
mirror surface require cleaning. The reflected light detector receives light through a 0.8
mm hole in the chamber housing and should not normally require attention.
When in the AUTO MODE, the Series 4000 instrument activates an Automatic Balance
Compensation system (ABC) on a regular basis to compensate for contamination of
these optical components. However, this ABC system, or the manual balance system,
has a finite limit of effectiveness beyond which compensation cannot be ensured. When
this limit is reached the red ABC STATUS LED on the monitor front panel will light,
warning of heavy contamination. At this point it is necessary to clean not only the mirror
surface but also the light guide ends.
6.1.1 Cleaning Procedure
(a)
Ensure that all surfaces are at a temperature above that of the freezing
point of the cleaning fluid.
(b)
Remove the metal sensor sealing cap assembly at the front of the sensor
unit (including black plastic plug or microscope) by unscrewing it in an anti-
clockwise direction. Take care not to misplace the "o" ring seal which seats
in the PTFE block and seals against the quartz glass viewing window.
(c)
Check the "o" ring seal for damage and replace if necessary.
(d)
As a general rule, clean the mirror and light guide ends with a Q-tip soaked
in distilled water.
If contamination is oil-based then one of the following solvents may be used
instead of distilled water: methanol, ethanol, isopropyl alcohol.
A spray may be used along with a Q-tip wool bud as long as it does not
leave a film coating on the optics and providing it contains only the
recommended solvent as above. Take care not to leave deposits on any of
the optical surfaces
.
