INFICON BCG450 ATM to Ultra-High Vacuum Triple Gauge - Manual (Page 27)

tina40e1-b (2011-04)
27
Due to the capacitance diaphragm sensor used in the upper pressure range, a
minimized gas type dependence is achieved.
Pressure range Measuring principle Gas type dependence
10 … 1500 mbar
capacitance diaphragm
sensor independent of gas type,
no correction required
1 … 10 mbar
capacitance diaphragm
sensor and Pirani sensor
crossover range
2×10 -2 … 1 mbar Pirani sensor 1)
5Ч10 -3 …
2Ч10 -2 mbar
Pirani sensor and
hot cathode ionisation sen-
sor (BA)
crossover range
5Ч10 -10 …
5Ч10 -3 mbar
hot cathode ionisation sen-
sor (BA)
1)
1) Pressure indicated applies to dry air, O
2
, CO and N
2
and has to be converted
for other gases ( → Appendix B).
The analog measuring signals of the BA and Pirani sensors are converted into a
digital form by a micro-controller and subsequently converted to a value represent-
ing the measured total pressure. After further processing this value is available as
an analog measurement signal (0 … +10.13 V) at the output (sensor cable con-
nector Pin 2 and Pin 12). The maximum output signal is internally limited to
+10.13 V (1500 mbar). The measured value can be read as digital value through
the RS232C interface (only BCG450) (Pins 13, 14 and 5) (
→ 33). 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 (only BCG450) (
→ 33).
In addition to converting the output signal, the micro controller's functions include
monitoring of the emission, calculation of the total pressure based on the meas-
urements of the three sensors, and communication via RS232C interface (only
BCG450).
With the built-in atmoshere switching function an atmospheric pressure threshold
can be programmed. If the pressure rises above this value a (semi conductor) relay
"atmospheric pressure reached" is activated. The thresold can be programmed by
the user as a percentage of the actual atmospheric pressure (ambient).
These gauges can be used in a network together with other equipment meeting the
respective standards. Technical data, interface and communication is described in
separate sections (
→ 38 for DeviceNet and 40 for Profibus).
Two adjustable switching functions are integrated in the gauge. The corresponding
relay contacts are available at the sensor cable connector (
→ 8, 20, 41).
The basic sensor and sensor electronics of all BCG450 versions are identical.
Gas type dependence
4.2 Operational Principle of
the Gauge
Field Bus Versions
(BCG450-SD, BCG450-SP)