Varian 990 dCLD II, Operation Manual

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Model 990 dCLD II Component Leak Detector
3-12
NOTE
No ZEROing takes place during an EXTERNAL calibration
because the 990 dCLD II has no control over the external
calibrated leak.
The SPEC TUBE LED on the front of the control unit flashes while
calibration is taking place, the Discrete I/O J3/22 is active, and the
response to the inquiry ?STATUS<CR> includes CAL. If the optional
front control panel is installed, the calibrate indicator LED lights
while calibration is taking place.
To set the mode to FAST, issue the 1 INIT-QUICK-CAL<CR> com-
mand or, if the optional front control panel is installed, select FAST
from the CAL LEAK SET-UP screen (Section 4.6.1 “Calibrated Leak
Set-Up” on page 4-13).
ZERO The ZERO function reads the background leak rate signal, stores
the reading in memory, and then resets the zero reference point.
Subsequent actual test measurements include both helium from the
real leak and helium from background conditions, however, the
recorded background signal from the measurement is subtracted
and the resultant real leak rate is displayed.
NOTE
Performing the ZERO function while introducing helium to the
test object can result in the suppression of a real leak. Only use
the ZERO function after the helium source has been removed.
To perform a ZERO function, assert J3/7 in the discrete I/O, issue
the ZERO<CR> command or, if the optional front control panel is
installed, press the ZERO button (Section 4.1 “Control Buttons” on
page 4-2).
ENABLE or DISABLE
REJECT SET POINTS Each REJECT SET POINT must be enabled before the function is
operational. Conversely, each must be disabled to stop its opera-
tion.
To ENABLE set points, issue the ENABLE- n REJECT<CR> command,
where n is equal to 1 through 4. If the optional front control panel
is installed, enable individual reject set points by setting the ON/
OFF buttons located to the right of each set point field to ON in the
Reject and Audio Set Points screen (Section 4.6.2 “Reject and
Audio Set Points” on page 4-14).
To DISABLE set points, issue the DISABLE- n REJECT<CR> com-
mand, where n is equal to 1 through 4. If the optional front control
panel is installed, disable individual reject set points by setting the
ON/OFF buttons to OFF in the Reject and Audio Set Points screen
(Section 4.6.2 “Reject and Audio Set Points” on page 4-14).