8270A/8370A
Operators Manual
46
6. Use the bleed valve to adjust the pressure/vacuum to 0.08 kPa absolute
(
0.01 kPa) and allow the pressure to stabilize.
7. Read the pressure indication from the Vacuum Reference (not on the
Product) and enter the value in the
Vacuum Reading
field and select the
Zero
button from the Zero Module menu. The PMM pressure indication
reflects the zero-corrected pressure when the zeroing process is complete.
8. Select the
to view the zOffset (AutoZero) value in the Calibration
Coefficients section of the screen.
PM500 Full Scale >700 kPa Absolute Zeroing
Zero correction in absolute mode is automatic when a module is selected as the
AutoZero reference and the system is vented.
Ensure a sufficiently-accurate module is available if you use automatic zeroing.
Table 17 lists the maximum allowable uncertainty required to zero the PMM.
If a module is not selected as an AutoZero reference, use manual zeroing mode
to zero the PMM.
Tasks
Tasks are pre-programmed routine functions that quickly perform common tests
and tasks. The tasks are: Leak Test, Switch Test, Exercise, Program, CPS
Cleanout and CPS Purge.
Note
CPS tasks are greyed out and disabled if the CPS is not turned on in
the settings.
Leak Test
This function performs an automated leak test to show the rate of pressure loss.
To determine this, the Product uses the settings in the test to set the pressure to
a Setpoint value. Once stable, the Product turns off pressure control to measure
the pressure loss. To help determine if a leak is external to the system or inside
the system, the leak test mode can be changed to internal or external. To run an
internal leak test the optional external isolation valve accessory must be installed.
To run a leak test, set a few parameters to tell the Product how to perform the
leak task. Those parameters are:
Setpoint Pressure
– The target pressure of the test.
Stability
– This tells how long the pressure is dynamically stabilized at the
Setpoint before the test starts. The test does not start until the Product shows the
ready indication for the amount of time prescribed.
Duration
– After reaching the stability time, the test starts and the Product
changes to Measure mode. The system then measures the rate of pressure loss.
When the test ends, the average rate of pressure loss per minute is shown.
