Leakage Current Check - Agilent Technologies VacIon Plus 800 Manual Del Usuario

Technical Information

Leakage Current Check

If the pump current reading is used as a pressure measurement, it is worth
checking the pump leakage current as follows:
1 Turn off the pump control unit.
2 Remove the pump pole piece (magnetic circuit). Contact the local Agilent
Technologies representative to get indication about how this operation should
be carried out.
3 Turn on the pump control unit and wait for current stabilization. The current
reading should not be higher than 500 nA. Make sure that the control unit and
the high voltage cable leakage current is negligible.
4 If the reading is higher than 500 nA, this indicates that leakage current comes
from the pump; in this case you should perform a "high-potting" per the
following procedure, then recheck the pump and re-install the pole piece.
5 If it is not possible to "high-pot" the pump, the pressure reading is biased by the
leakage current value.
If, for any reason, it is not possible to remove the pole piece, the presence of
leakage current can be evaluated by changing the high voltage applied to the ion
pump from 7 kV to 3 kV. This reduces exponentially the leakage current, thus
confirming that the current reading is affected by leakage.
Agilent VacIon Plus 800 User Manual 231