Ludlum Measurements 3100, Руководство пользователя

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2-3
d. The SAMPLE mode turns on the internal air pump and allows the unit to pull air through the tritium
chamber while displaying the current measured tritium concentration. Note that the response time is
approximately 60 seconds. High levels of tritium may cause the “Alrm” message to appear on the display,
and for a loud “beeping” audio signal to be sounded. Low airflow levels (possibly caused by pinched
tubing or a dirty particulate filter) will result in a "Fail Air" text on the display.
e. The PURGE selection turns the air pump on and (when mains power is available) activates a heater in the
tritium chamber to drive out tritium and/or moisture from the chamber. This mode is used whenever it is
suspected that tritium has been adsorbed into the internal chamber walls, resulting in persistent high counts.
This condition may occur especially when measuring high levels of tritium in a humid environment. Before
starting the PURGE mode, the user should ensure that the air intake is sampling clean non-tritiated air.
During the purging operation, it is also recommended to switch the airflow desiccant to IN-LINE so that
dry air is entering the chamber. The PURGE mode will activate both the air pump and the internal heater,
which has a thermostat set to limit the internal temperature to 149 °F (65 °C). The purge mode has a
duration of 7200 seconds (2 hours) and countdown timer, shown on the display. The user should check
after a purge cycle is complete and the instrument has returned to normal operation temperatures to see if
the tritium level in the instrument has been reduced to normal levels. It may be necessary to repeat the
purge cycle if the tritium level is still above normal.
2.2.1.5 Alarm Point Potentiometer. This flat screwdriver-adjustable 295-degree rotary potentiometer adjusts
the tritium alarm threshold from 0 (OFF) to 10,000 µCi/m
3
or equivalent SI units (MBq/m
3
). Whenever this control
is adjusted, the display screen temporarily switches to displaying the adjusted alarm point value. The alarm point
value may only be set while CHECK mode is selected. As the potentiometer is rotated and the units are set to
µCi/m
3
, the amount of change varies by 5 while the value is less than 100, varies by 50 when the value is between
100 and 1000, and varies by 500 when the value is greater than 1000. The pop-up alarm point screen MUST be
allowed to close (approximately three seconds with no change) and return to the check screen in order to save the
new alarm point value. When the instrument is set to utilize MBq/m
3
units, the rate of change is equivalent to the
same values in µCi/m
3
.
Note: The software allows the user to establish a second non-latching alarm point labeled “Alert,” independent of
the user-settable (screwdriver-adjustable) alarm point.
2.2.1.6 Circuit Breaker. Located on the back side of the instrument, this toggle switch, normally in the ON or up
position, allows mains AC power from the power cord to power the instrument (automatically switching over from
battery power) and recharges the internal AA batteries if needed. The circuit breaker protects the instrument and will
disconnect the AC power if more than 2A is pulled by the instrument, and the toggle switch will automatically move
to the OFF position. This switch may be used by the user as a power selector switch to disconnect AC power and
force the primary AA batteries to supply power to the instrument.
2.2.1.7 AC Power Cord. The AC power cord connects to the receptacle on the back of the instrument. To
connect the power cord, align the AC plug with the receptacle, and push firmly in. See Figure 2-2. A slight click
may be heard from the locking mechanism. To disconnect the power cord, pull back on the blue housing while
holding the cord grip, as shown in Figure 2-3. Failure to pull back on the blue housing properly may result in
breakage of the internal locking mechanism inside the AC plug. If this happens, the AC power cord will still
function, but not be securely held in place.