990 CLD Autoline™ Leak Detector
DR
AFT 2/2/04
4-11
3. Use a DC voltmeter to measure the voltage between test points TP4 (Gnd) and TP5 (+).
CAUTION
Adjusting the voltage in the following step to more than
1.50 VDC may shorten the life of the ion source filaments.
4. Adjust the screwdriver EMIS control to peak the leak rate display.
When tuning, the emission control may be re-adjusted to obtain more sensitivity,
however, the preceding Caution should be carefully noted. See
“Tuning the Spectrometer Tube Using a Helium Reservoir Leak” on page 3-6.
5. Tune and calibrate the leak detector in accordance with “Tuning the Spectrometer Tube
Using a Helium Reservoir Leak” on page 3-6.
Ion Source Voltages Range Validation
Sometimes it is important to know if the ion source tuning voltages have sufficient span or
are in the correct range. This is especially true after ion source replacement or when it is not
possible to tune the spectrometer tube so that it is sensitive to helium. Comparison with the
following steps indicates if the voltages are in the correct range.
To check the ion source voltages:
1. Set the ION and FOCUS controls fully counterclockwise.
2. Set the RESIDUAL BACKGROUND switch to the CHECK position.
3. Using a voltmeter with an input impedance of at least 100,000 Ohms/V, measure the
ion voltage between test points TP1 (+) and TP4 (-) on the front panel, then rotate the
ION control fully clockwise and measure the voltage again.
The following readings should be obtained (± 10%):
TPI -TP4
Ion Voltage ccw = 160 VDC
cw = 330 VDC
Leave the ION control in the fully clockwise position.
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