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Model T101 Instruction Manual Troubleshooting & Service
235
be re-entered before the instrument will function correctly. Also, zero and span
calibration should be performed.
1. Document all analyzer parameters that may have been changed, such as
range, auto-cal, analog output, serial port and other settings before
replacing the DOM
2. Turn off power to the instrument, fold down the rear panel by loosening
the mounting screws.
3. When looking at the electronic circuits from the back of the analyzer,
locate the Disk-on-Module in the right-most socket of the CPU board.
4. The DOM should carry a label with firmware revision, date and initials of
the programmer.
5. Remove the nylon fastener that mounts the DOM over the CPU board,
and lift the DOM off the CPU. Do not bend the connector pins.
6. Install the new Disk-on-Module, making sure the notch at the end of the
chip matches the notch in the socket.
7. It may be necessary to straighten the pins somewhat to fit them into the
socket. Press the DOM all the way in and reinsert the offset clip.
8. Close the rear panel and turn on power to the machine.
9. If the replacement DOM carries a firmware revision, re-enter all of the
setup information.
9.6.2. ADJUSTING THE UV LAMP (PEAKING THE LAMP)
There are two ways in which ambient conditions can affect the UV Lamp output and
therefore the accuracy of the SO
2
concentration measurement: lamp aging and lamp
positioning.
Lamp Aging - Over a period of months, the UV energy will show a downward trend
and can be up to 50% in the first 90 days, and then a slower rate, until the end of useful
life of the lamp. Periodically running the UV lamp calibration routine (refer to Section
4.6.6) will compensate for this until the lamp output becomes too low to function at all.
NOTE
As the lamp degrades over time, the software for the CPU compensates for the loss of
UV output.
Lamp Positioning – The UV output level of the lamp is not even across the entire length
of the lamp. Some portions of the lamp shine slightly more brightly than others. At the
factory the position of the UV lamp is adjusted to optimize the amount of UV light
shining through the UV filter/lens and into the reaction cell. Changes to the physical
alignment of the lamp can affect the analyzers ability to accurately measure SO
2
.
07266B DCN6485