Veeco MS40 Operation And Maintenance Manual page 63

that once the START pushbutton is pressed, the unit is placed in its
STANDBY mode (without any venting the test port). If the VENT button is
depressed for a period of time (as adjusted by the User, see Section 2.7 for
instructions on setting this "delay") the unit will open the vent valve. The
opening of the vent valve brings the test object back to atmospheric pressure,
thereby allowing it to be removed from the leak detector's test port. The
duration of venting is also adjustable (again see Section 2.7 for instructions on
setting the delay of the venting period). If the ambient air in the testing area
has a high moisture content, it is advisable to vent the unit with dry nitrogen.
Using dry nitrogen prevents water vapor from collecting in the unit, which
then must be pumped out during the next testing cycle.
The MS-40 is automatically tuned and calibrated by using the factory-
installed temperature compensated helium standard, traceable to NIST, as
a reference. During tuning, the unit's computer controls the vacuum
system's valves and adjusts the various voltages of the mass spectrometer
to obtain an optimum response to the helium signal from the reference
standard. After the voltages are optimized, the gain of the amplifier is
adjusted until the displayed leak rate value corresponds to the temperature
compensated value of the helium standard.
In the Sniff Test Mode, the sniffer port has a direct internal connection to
the test port. The flow rate of the sniffed gases is limited by the size of
the fixed leak in the sniffer probe.
In the event of a power failure, all valves within the vacuum system will
automatically close. The mechanical pump will shut off, the turbo-
molecular pump will also shut off, however, it will take several minutes
for the blades of the pump to stop spinning. When power is again
available, the unit will automatically begin its normal "power-up"
sequence. If, before the power failure, the filament was activated, the unit
will power-up with the filament on. If the filament was off prior to power
loss, the User will have to manually activate the filament (by pressing the
FIL ON momentary switch located on the User Panel).
Vacuum Instrument Corp.
2099 Ninth Avenue
Ronkonkoma, NY 11779
631.737.0900
1109-186-00 Rev. C 3-10