Adjustment And Maintenance Of The Vacuum Sensor Vsp62; Maintenance Of The Vacuum Sensor; Replacement And Adjustment - Fisher ALPHA 1-2 LDplus Operating Manual

7.3. Adjustment and Maintenance of the Vacuum
Sensor VSP62
7.3.1.

Maintenance of the Vacuum Sensor:

7.3.2.

Replacement and adjustment

56 • Maintenance
The tungsten wire has a limited service life because it easily reacts
with ambient gases. Tungsten reacts especially with carbons to build
tungsten carbide. The wire becomes short and breaks. Therefore, the
only possibility to enlarge the service life of PIRANI sensors is to a v o
i d every contact to carbonic substances.
At the end of the drying process vent the freeze drying unit and
remove the dry product. Then defrost the unit with open drain valve
with warm water (max. +50°C). Finally it is necessary to wipe the ice
condenser chamber dry.
It is n o t recommended to defrost the unit simply by leaving it at room
temperature over a long period of time. In this case the tungsten wire
reacts with the ambient atmosphere!
After defrosting and drying the unit, it is additionally recommended to
evacuate the unit for 30 minutes with o p e n gas ballast valve. All
residues that may harm the tungsten wire are removed in this way.
The vacuum sensor has to be replaced if "---" is shown in the vacuum
field after the aeration of the system instead of "Atm" and if the
process and equipment information window shows the message
"Vacuum sensor defective". If after the warm-up phase and the
aeration of the unit the vacuum display still does not show "Atm" but a
value equal to or smaller than 900 mbar, the vacuum sensor has to be
readjusted. The warm-up phase of the vacuum sensor takes at least 5
minutes.
7.3.2.1 Vacuum sensor adjustment
The vacuum sensor has two adjustment buttons labelled "adj" and
"set". The buttons are protected by protective caps. Remove the
protective caps of the buttons prior to adjusting the sensor. Use a
small pen (max. ∅ 2.5mm) to actuate the buttons. Refit the protective
caps after the adjustment.
A digital readjustment to atmospheric pressure (Atm) and zero is
possible directly at the vacuum sensor using the button labelled "adj"
(adjust). The measuring transducer automatically recognises the
adjustment point. If a zero adjustment has to be performed, the actual
pressure should be smaller than 5.0x10
Alternatively, the sensor can also be adjusted to a reference value
-5
mbar (factory setting).
Operating Manual Freeze Dryer ALPHA 1-2 LDplus