VS Series Helium Mass Spectrometer Leak Detectors
2-18
DRAFT 4/
23/15
Internal Leak Value The temperature-compensated internal leak value and expiration
date appear to the right of the Internal Leak Value text. The actual
Internal Leak Value and Expiration Date can be modified using the
Internal Calibration Leak screen (
Section 3.1.8.3.1 “Cal Leak Expi-
ration Set-Up” on page 3-23).
External Leak Value Displays the value on an operational button.
To configure a n e x ternal leak:
1. Press External Leak (located under Calibrate With).
2. Press the button to the right of the External Leak Value text.
The data entry pad appears.
3. Enter the leak value and press OK.
For calibration in the E-10 range, the vacuum system must be sufficiently pumped to reduce
helium background below the E-10 range signal level. This is required to achieve an
acceptable signal-to-noise level and ensure accurate calibration.
E-10 range calibration is performed using an external calibrated leak. If an external
calibration is selected soon after system startup, the VS system evaluates the helium
background and determines if the background signal is sufficiently low to give an accurate
calibration. If the:
❑ System has pumped out sufficiently, the calibration proceeds.
❑ Background is changing, indicating the system is still pumping away background
helium, a countdown timer appears (
Figure 2-9). The VS system monitors the helium
background and shows the time until the calibration begins. Should you prefer not
to wait, a Cancel button permits the calibration request to be canceled.
NOTE The firmware initially starts at a large time interval, but
recalculates the required time as the pumping continues. The
new time is reflected on the timer.
Figure 2-9 Helium Background Timer
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