INFICON BCG450-SP ATM to Ultra-High Vacuum Triple Gauge (Profibus) User Manual
Page 33
tira41e1 (2005-06) BCG450SPv1.cp
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Instances 5 and 6 of the Analog Sensor Input Function Block describe the func-
tionality of the two switching functions (Setpoint A / Setpoint B) of the gauge
(setting the switching functions
→ [2], [3]):
Instance
Setpoint
5
A
6
B
With Process Values (ID 19), the current threshold setting (made by means of the
potentiometers) is read; with Status, the relay status (open/closed) can be read.
ID
Name
Structure Data type
Bytes
Access
Store
19
Process Value
(PV)
Simple
Unsigned16
-
1_R
2_R
D
20
Status
Simple
Unsigned8
1
1_R
2_R
D
21
Data Type
Simple
Unsigned8
1
2_R
2_W
N
22
Data Units
Simple
Unsigned16
2
2_R
2_W
N
23
Reading Valid
Simple
Boolean
1
1_R
2_R
D
201
Setpoint
Function
Simple
Boolean
1
1_W
2_W
N
202
Percentage of
atmosphere
Simple
Unsigned 16
2
1_W
2_W
N
203
Atmospheric
pressure
reached
Simple
Boolean
1
1_W
2_W
D
The Process Value contains the current setting of the threshold potentiometers for
"Setpoint A" and "Setpoint B" in the currently selected data unit and data type.
If the pressure drops below the set threshold, the relay is closed. If after that, the
pressure rises above that threshold with a hysteresis of 10%, the relay is opened
again (
→ [2], [3]).
The Process Value PV is output in the currently selected data unit and data type.
Values output in the pressure unit COUNTS can be converted into a pressure value
by means of the following formulas:
p
mbar
=
10
(COUNTS / 2000) - 12.5
The threshold voltages of the Setpoint potentiometer converted into a pressure
value by means of the following formulas:
p
mbar
=
10
(1.23011 × U) - 9.30102999
Where:
U is the threshold voltage [V] of the corresponding Setpoint (A, B),
measured at the D-Sub connector (sensor cable connector) of the gauge
(
→ [2], [3]).
The upper pressure limit of the gauge is 1500 mbar
⇒ the resulting
pressure value of the attribute "Percentage of Atmosphere" must be less
than 1500 mbar, otherwise the relay may never be set. The allowed
range for "Percentage of Atmosphere" is 1 … 140%.
3.2.5 Analog Sensor Input
Function Block
Instances 5 and 6 /
SLOT 1
3.2.5.1 Process Value