Model 990 dCLD II Component Leak Detector
3-15
AUTO-ZERO<0
ACTIVE
When AUTO-ZERO<0 is activated, it automatically adjusts the
zero reference point back up to zero when the helium level drops
below the previously set zero reference point. This feature ensures
that the leak detector maintains calibration after a previously
zeroed background signal naturally cleans up. The factory default
setting is active.
If the optional front control panel is installed, when the
AUTO-ZERO<0 feature is in the process of re-adjusting the zero
reference point, the UNDER light indicator located on the left end
of the bar graph illuminates.
The duration of time that the UNDER light stays on during this pro-
cess is a function of how much helium is cleaning up and how fast
it is cleaning up. If the magnitude of helium clean up is great, the
UNDER light remains lit until the clean up rate has slowed or stabi-
lized. Although leaks can be located in this state, quantitative test-
ing must not be performed until the UNDER light is off. Occasional
flashing of the UNDER light indicates normal minor adjustments to
small changes in background. This does not impact the leak detec-
tor’s ability to accurately locate and measure leaks.
To set AUTO-ZERO<0 to active, issue the 1 INIT-AZ<0<CR> com-
mand or, if the optional front control panel is installed, set the
mode via the Zeroing screen (Section 4.6.6 “Zeroing” on
page 4-17).
AUTO-ZERO < 0
INACTIVE
When AUTO-ZERO<0 is inactive, the leak detector does not auto-
matically adjust the zero reference point back up to zero when the
helium level drops below the previously set zero reference point.
When this occurs, issue the ZERO command to re-adjust the zero
reference point manually.
If the optional front control panel is installed, the UNDER light
remains lit, indicating that the background level is below the previ-
ously set zero reference point. Press the
ZERO
button on the front
panel to re-adjust the zero reference point manually. This clears the
UNDER light indication.
To set AUTO-ZERO<0 to inactive, issue the 0 INIT-AZ<0<CR>
command or, if the optional front control panel is installed, set the
mode via the Zeroing screen (Section 4.6.6 “Zeroing” on
page 4-17).
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