Ulvac HELIOT 301, Instruction Manual

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4-3-2 Setting the SEN. switch
The SEN. switch changes over the sensitivity of this instrument. The ratio of helium
molecules that reach the analyzer tube, that is, amount of helium detected can be controlled
by changing over the switch to control the revolution of the compound molecular pump.
!
CAUTION
Setting timing
Perform the operation to change the setting of the SEN. switch, with the
instrument completely shut down (compound molecular pump shut
down).
If the instrument is restarted by changing the setting immediately after
termination of the stop mode (when the compound molecular pump is
still rotating), malfunction can result.
<Sensitivity L>
Normal sensitivity. Set it in the L position of the SEN. switch. The revolution of the
compound molecular pump is 90000 rpm, which is the normal revolution.
<Sensitivity H>
Sensitivity is high. Set it in the H position of the SEN. switch. The revolution of the
molecular compound pump is controlled at 70% of normal revolution (63000 rpm). As
compared with L sensitivity, the test port connecting pressure is lower and helium cleanup
time is longer.
SEN. L SEN. H
Flow Connecting
pressure
Sensitivity range Connecting
pressure
Sensitivity range
Gross leak flow 1000 E-9 to E-4 500 E-10 to E-5
Middle leak flow 70 E-10 to E-5 18 E-11 to E-6
Fine leak flow 10 E-11 to E-6 3 E-12 to E-7
Auto flow 1000 E-11 to E-4 500 E-12 to E-5
(Unit of pressure: Pa) (Unit of sensitivity: Pam
3
/sec)
Method of setting
After verifying that the main power is turned OFF, change over the SEN. switch on the
connector panel. Then start up the instrument as usual and perform operation, including test
and others.