INFICON BPG402-Sx ATM to Ultra-High Vacuum Gauge - Manual (Page 27)

tina46e1-a (2010-03) BPG402.om
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The analog measuring signals of the Bayard-Alpert and Pirani sensors are con-
verted into a digital form by a micro-controller and subsequently converted to a
value representing the measured total pressure. After further processing this value
is available as analog measurement signal (0 … +10 V) at the output (sensor cable
connector Pin 2 and Pin 12). The maximum output signal is internally limited to
+10 V (atmosphere). The measured value can be read as digital value through the
RS232C interface (Pins 13, 14, 5) (
→ 30). Gauges with a display show the value
as pressure. The default setting of the displayed pressure unit is mbar. It can be
modified via the RS232C interface (
→ 30).
In addition to converting the output signal, the micro controller's functions include
monitoring of the emission, filament status, calculation of the total pressure based
on the measurements of the two sensors, and communication via RS232C inter-
face.
When the operating voltage is supplied ( → Technical Data), the output signal is
available between Pin 2 (+) and Pin 12 (–) of the sensor cable connector
(Relationship Output Signal – Pressure
→ Appendix A).
Allow for a stabilizing time of approx. 10 min. Once the gauge has been switched
on, permanently leave it on irrespective of the pressure.
Communication via the digital interfaces is described in separate sections.
Gauge failures due to contamination, as well as expendable parts
(filament), are not covered by the warranty.
Deposits on the electrode system of the Bayard-Alpert gauge can lead to unstable
measurement readings.
The degas process allows in-situ cleaning of the electrode system by heating the
electron collector grid to approx. 700 °C by electron bombardment.
Depending on the application, this function can be activated by the system control
via one of the gauges digital interfaces. The gauge automatically terminates the
degas process after 3 minutes, if it has not been stopped before.
The degas process should be run at pressures below 7.2×10
-6
mbar
(emission current 5 mA).
For a repeated degas process, the control signal first has to change from ON
(+24 V) to OFF (0 V), to then start degas again with a new ON (+24 V) command. It
is recommended that the degas signal be set to OFF again by the system control
after 3 minutes of degassing, to achieve an unambiguous operating status.
A new degas cycle can only be started after a waiting time of
30 minutes.
Degas acts only upon the active filament.
4.2 Operational Principle of
the Gauge
4.3 Putting the Gauge Into
Operation
4.4 Degas
Contamination