INFICON VSC150A absolute switch, passiv - Manual (Page 14)

2.3.1.1 Setting Switching Pressures Higher than 20 mbar
Condition: Correct basic adjustment of the Vacuum
Switch.
Basic adjustment of the switch in the factory provided
that at equal pressure in sensing and reference chamber
the contact is just closed.
The diaphragm (1/3) touches the contact pin (1/6) in the
reference chamber (1/5).
Check this basic adjustment.
Open adjusting valve (1/4) resp. (6/4) using an Allan key
(size across flats 5 mm) by 2 anticlockwise turns.
The relay contact via terminals 11 and 12 in the connec-
ted SV switching amplifier must now be open (Fig. 5).
If not, remove protective cap (6/1) and turn adjusting
screw (6/2) carefully clockwise till the relay is de-energi-
zed and the above-mentioned contact is open.
Then replace protective cap (6/1).
Now set desired switch point as follows:
- At first produce desired pressure in the system.
- Then close adjusting valve (6/4) turning clockwise with
the dynamometric key.
Note
The amount of torque for the adjustment valve is
Md = 3.5 to 4 Nm.
- If the pressure in the sensing chamber drops by 0.1
mbar the contact between diaphragm and contact pin
opens by flexing of the diaphragm and the relay in the
connected switching amplifier is energized.
- The switch contact on terminals 11 and 12 (see Fig. 5)
is closed.
2.3.1.2 Setting Switching Pressures Lower than 20 mbar
The procedure is basically the same as described in
2.3.1.1.
Caution However, to avoid contamination of the
reference chamber it is essential to use
only extremely dry and clean gas. Other-
wise there is a risk that gas (vapor)
desorption from the chamber walls will
change the pressure in the reference
chamber.
The system must be pumped down to a pressure less
than 1·10
-4 mbar.
Open adjusting valve (6/4) using an Allan key (size
across flats 5 mm) by 2 anticlockwise turns.
Bake out the Vacuum Switch using strip heaters for at
least 5 to 6 hours at approx. 120
°
C, while pump down
continues uninterrupted.
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14
tina42e1 (2005-03) VSC150.ga
tina42e1 (2005-03) VSC150.ga
2.3.1.1 Setting Switching Pressures Higher than 20 mbar
Condition: Correct basic adjustment of the Vacuum
Switch.
Basic adjustment of the switch in the factory provided
that at equal pressure in sensing and reference chamber
the contact is just closed.
The diaphragm (1/3) touches the contact pin (1/6) in the
reference chamber (1/5).
Check this basic adjustment.
Open adjusting valve (1/4) resp. (6/4) using an Allan key
(size across flats 5 mm) by 2 anticlockwise turns.
The relay contact via terminals 11 and 12 in the connec-
ted SV switching amplifier must now be open (Fig. 5).
If not, remove protective cap (6/1) and turn adjusting
screw (6/2) carefully clockwise till the relay is de-energi-
zed and the above-mentioned contact is open.
Then replace protective cap (6/1).
Now set desired switch point as follows:
- At first produce desired pressure in the system.
- Then close adjusting valve (6/4) turning clockwise with
the dynamometric key.
Note
The amount of torque for the adjustment valve is
Md = 3.5 to 4 Nm.
- If the pressure in the sensing chamber drops by 0.1
mbar the contact between diaphragm and contact pin
opens by flexing of the diaphragm and the relay in the
connected switching amplifier is energized.
- The switch contact on terminals 11 and 12 (see Fig. 5)
is closed.
2.3.1.2 Setting Switching Pressures Lower than 20 mbar
The procedure is basically the same as described in
2.3.1.1.
Caution However, to avoid contamination of the
reference chamber it is essential to use
only extremely dry and clean gas. Other-
wise there is a risk that gas (vapor)
desorption from the chamber walls will
change the pressure in the reference
chamber.
The system must be pumped down to a pressure less
than 1·10
-4 mbar.
Open adjusting valve (6/4) using an Allan key (size
across flats 5 mm) by 2 anticlockwise turns.
Bake out the Vacuum Switch using strip heaters for at
least 5 to 6 hours at approx. 120
°
C, while pump down
continues uninterrupted.