Model 990 dCLD II Component Leak Detector
3-18
3.4.3 Tuning
The 990 dCLD II is tuned to the spectrometer assembly at the factory. In normal operation,
the 990 dCLD II upon issue of the CALIBRATE<CR> command or upon request via the
optional front control panel (press the CALIBRATE button) performs a calibration to the
value of the calibrated leak in the system or to the value of an external leak. If you are cali-
brating to an external leak, it should be rough pumped before opening the isolation valve to
avoid excessive pressure and helium signal burst. A leak calibrated to the middle two
decades of the four decades of range based upon your system configuration is recom-
mended for use during the calibration routine.
Manually tuning (see Section 5.6 “Manual Tuning” on page 5-20) the 990 dCLD II is more
likely to be necessary if:
❑
The control unit is connected to a spectrometer assembly in the field other than the
one with which it was tested
❑
It cannot successfully CALIBRATE (respond
yes
to ?CALOK<CR>)
❑
The gain (?GAIN<CR>) is greater than 5.0
❑
A board in the Platform is changed
❑
The ion source is changed
3.4.4 Running
The 990 dCLD II senses the level of helium in the foreline of the high vacuum pump and
converts the signal into a leak rate based upon the latest calibration and zero parameters in
memory.
The leak rate is always available:
❑
Through the host serial port (J6) by entering the ?LEAK<CR> command
❑
By measuring the voltage at the analog voltage output on J3
❑
By reading the BCD output on J4
If the optional front control panel is installed, observe the leak rate bar graph display or the
leak rate displayed in the Home screen (Section 4.4 “Touch Panel Home Screen” on
page 4-7).
The leak rate is valid if the READY line in the discrete I/O is active (?STATUS<CR> response
contains RDY). In the event that the ready line is
inactive
, (?STATUS<CR> response contains
RDY/) a leak rate might be able to be read, but it would not be a valid leak rate. For exam-
ple, if the active ion source filament is burned out, READY would be inactive and
FILAMENT FAULT would be active. This causes the host computer or PLC to halt testing and
signal for help. Appendix B “Customer Accessible Inputs and Outputs”contains a descrip-
tion of the available discrete I/O lines in the 990 dCLD II.
Содержание 990 dCLD II
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