Model 2280A
31
7.0 Appendix
7.1 Warranty
General Monitors warrants the Model 2280A to be free from defects in workmanship or
material under normal use and service within two years from the date of shipment.
General Monitors will repair or replace without charge any such equipment found to be
defective during the warranty period. Full determination of the nature of, and
responsibility for, defective or damaged equipment will be made by General Monitors’
personnel.
Defective or damaged equipment must be shipped to General Monitors’ plant or
representative from which the original shipment was made. In all cases this warranty is
limited to the cost of the equipment supplied by General Monitors. The customer will
assume all liability for the misuse of this equipment by its employees or other personnel.
All warranties are contingent upon proper use in the application for which the product
was intended and does not cover products which have been modified or repaired
without General Monitors’ approval, or which have been subjected to neglect, accident,
improper installation or application, or on which the original identification marks have
been removed or altered.
Except for the express warranty stated above, General Monitors disclaims all warranties
with regard to the products sold, including all implied warranties of merchantability and
fitness and the express warranties stated herein are in lieu of all obligations or liabilities
on the part of General Monitors for damages including, but not limited to, consequential
damages arising out of, or in connection with, the performance of the product.
7.2 Sensor
Operating
Principle
GMI’s sensor is a solid-state, continuous, diffusion type element. The sensor uses the
ability of Hydrogen Sulfide to strongly and significantly adsorb onto certain materials as
the basis for measurement. Specifically, H
2
S adsorbs onto many different metals (as
well as many other materials, including numerous hydrocarbons, sulfur dioxide, and
other sulfur compounds). GMI has developed a proprietary metal oxide semi-conductor,
which is extremely selective in permitting H
2
S to adsorb onto it. That is, very few other
compounds found in practical applications will affect this metal oxide. The
semiconductor material is therefore specific to H
2
S.
The semiconductor is located in the system circuit, acting as a resistor. When air, which
contains H
2
S, diffuses into the sensor through the outer flame arrestor, the adsorption of
the H
2
S onto the semiconductor causes its electrical resistance to decrease. The sensor
is temperature controlled to prevent adsorption rate variations from ambient temperature
changes. The decrease in resistance is extremely repeatable over a range of 0-20, 0-50
or 0-100 ppm H
2
S. Therefore, the change produces a signal approximately proportional
to the logarithm of the H
2
S concentration. This signal is processed, linearized, and
displayed as a digital number on the front of the controller. The controller’s analog