INFICON BPG402-Sx ATM to Ultra-High Vacuum Gauge - Manual (Page 3)

tina46e1-a (2010-03) BPG402.om
3
Over the whole measuring range, the gauge has a continuous characteristic curve
and its measuring signal is output as logarithm of the pressure.
The gauge functions with a Bayard-Alpert hot cathode ionization measurement
system (for p < 2.0×10
-2
mbar) and a Pirani measurement system (for
p > 5.5×10 -3 mbar). In the overlapping pressure range of
2.0Ч10
-2
… 5.5Ч10
-3
mbar, a mixed signal of the two measurement systems is
output. The hot cathode is switched on by the Pirani measurement system only
below the switching threshold of 2.4×10
-2 mbar (to prevent filament burn-out). It is
switched off when the pressure exceeds 3.2×10
-2
mbar.
BPG402-Sx sensors are equipped with two hot cathodes. The identical filaments
are monitored by the gauge electronics. In case of a filament failure, the gauge will
switch over to the second (undamaged) filament and continue to operate. The
filament status is displayed on the gauge or can be read via the interfaces
(RS232C, DeviceNet or Profibus).
Functional Principle