30
GA130001441_002_C0
– 09/2016
6.4.4
THERMOVAC Alignment
Ageing and contamination of the sensor filament will impair the accuracy of the pressure
readout. For this it is recommended to align the THERMOVAC gauge head as required. For
this, the gauge head must be orientated in the same way in which it is subsequently
operated. The alignment process is run as follows:
Vent and the vacuum apparatus and adjust the 100% potentiometer at the THERMOVAC
gauge head so that the following readout is obtained:
Alignment too high
Alignment is precise
Alignment is too low
Figure 17
–
Full-scale alignment for the THERMOVAC gauge head
In order to ensure a stable but also precise alignment of the 100% point, the alignment
potentiometer (100%) should be turned further by 90° in the clockwise direction after the
indication of 1000 mbar has been displayed. Here the overrange indicator should just
come on.
Evacuate the vacuum apparatus to a pressure < 5·10
-4
mbar and adjust the “0”
potentiometer at the THERMOVAC gauge head so that the following reading is attained:
Alignment too high
Alignment is precise
Alignment is too low
Figure 18
–
Zero alignment for the THERMOVAC gauge head
Vent the vacuum apparatus and check the 100% setting once more. Correct a possible
deviation with the potentiometer.
If a correction of the 100% setting was necessary, then repeat the Zero adjustment.
