INFICON BCG450-SP ATM to Ultra-High Vacuum Triple Gauge (Profibus) - Manual (Page 23)

tira41e1 (2005-06) BCG450SPv1.cp
23
All gauge functions of the BCG450-SP are described in the Analog Input Block.
Since the gauge includes three measuring systems, there are also three Analog
Input Block Instances representing the Pirani measuring part, the ionization meas-
uring part (BA) and the capacitance diaphragm gauge part (CDG) respectively.
ID Name
1)
Structure Data type Bytes Access Store
16 Block Type Simple Octet string 4 2_R N
46 Channel Instance
Selector Simple Unsigned8 1 1/2_R/W N
47 PV Selector Simple Unsigned8 1 0_XI 1/2_R D
1)
The above parameters are described below.
The value of the Block Type ID is "3" (
→ table in Appendix A).
The gauge has three instances of the Analog Input Function Block and three in-
stances of the Vacuum Gauge Transducer Block, or one instance of each block per
measuring systems (Capacitance diaphragm sensor, Pirani and BA). There are two
additional instances for describing the switching functions (
→ section "Analog
Sensor Input Function Block", Instances 5 and 6).
However, there is only one address range for both, querying and setting the corre-
sponding parameters. The Parameter Channel Instance Selector is used for de-
fining the parameters that are written into the address range.
If the Parameter Channel Instance Selector is set to "1", the attributes of Instance 1
are mapped into that address range and can be written or read by addressing
Slot
⇒ Instance ⇒ Parameter-ID.
The PV Selector is determined by the gauge and defines the Analog Input Function
Block Instance from which the measured value is copied into the cyclic output data
telegrams. Therefore, the value output in the cyclic data is always the measured
value of the active instance, i.e. the one that is currently measuring. While the
gauge is measuring in the BA range, the measured value of the ionization vacuum
meter is output in the cyclic data and while the gauge is measuring in the Pirani
range, the measured value of the Pirani is output.
The measured values of Instances 5 and 6 (thresholds of the switching
functions) are not output in the cyclic data.
The pressure ranges, in which measurement is performed either by the Pirani
measuring part, by the BA measuring part or bye the Capacitance diaphragm sen-
sor measuring part, and which are thus called "active", are indicated below:
Pressure [mbar] active
instance
1 < p < 1500 CDG
5.5×10
-3
< p
≤ 10
Pirani
5×10
-10
< p < 2×10
-2
BA
In the pressure range 1 … 10 mbar and 5.5Ч10
-3
… 2Ч10
-2
mbar an averaging of
the two corresponding measurement principles is done. The definition of one
instance as the active instance in this pressure range is done approximately in the
middle of the crossover region.
3.2 Analog Input Block
3.2.1 One Of N Analog Input
Function Block / SLOT 1
3.2.1.1 Block Type
3.2.1.2 Channel Instance Selector
3.2.1.3 PV Selector
Measuring range