LEYBOLD 157 89, Manual

Page: 19 / 40

2.6.2 PM measurement channel
The PENNINGVAC measurement channel is supplied
factory-aligned and does not require any maintenance.
Test gauge T 35 may be used to check important equip-
ment functions. The test gauge is a gauge head simula-
tor for the PENNINGVAC gauge head. Different pressu-
re values are simulated via integrated resistors and are
available at three plug sockets.
The test values are indicated on the gauge head.
In the event of a fault in the measurement system test
gauge T 35 may be used to determine whether the fault
is with the gauge head, the gauge head cable or the CM
31 itself.
2.7 Alignment of the THER-
MOVAC gauge heads
Aging and contamination of the filament within the gauge
head will impair the accuracy of the pressure readings.
Therefore it is recommended to align the THERMOVAC
gauge heads from time to time when appropriate. This
alignment is carried out as follows:
Vent the vacuum system and adjust the 100 % potentio-
meter on the THERMOVAC gauge head so that the fol-
lowing bargraph display is obtained:
Note
In order to ensure a stable but none-the-less accurate
alignment of the 100 % value, the alignment potentiome-
ter (100 %) should be turned further by 90
°
in the clock-
wise direction after the last segment of the bargraph has
come on. When doing so, the right arrow (overrange)
may just come on.
Evacuate the vacuum system down to a pressure 5·10
-4
mbar and then adjust the „0“ potentiometer on the
THERMOVAC gauge head so that the following bargraph
display is obtained:
Vent the vacuum system once more and check the
100 % setting once more. If required correct any possi-
ble deviations.
If it was necessary to correct the 100 % setting, Zero ali-
gnment must be repeated.
Note
With the Torr setting the bar +3 is permanently switched
off.
2.8 Switching off
The instrument is switched off simply by disconnecting
the power cord.
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Alignment
too high
Alignment
exact
Alignment
too low
Alignment
too high
Alignment
exact
Alignment
too low