INFICON BCG450-SD ATM to Ultra-High Vacuum Triple Gauge (DeviceNet) - Manual (Page 28)

28
tira40e1 (2005-04) BCG450SDv1.cp
The setpoint function "Atmosphere Control" is used to decide whether the measu-
red pressure is within a specified percentage of the atmospheric pressure
(
→ diagram below).
Attribute 101 "Percentage of Atmosphere" is used to define the percentage of at-
mospheric pressure. If the measured pressure is within this window, the corre-
sponding relay will be activated (
→ [4]).
A fixed hysteresis of 2% of the atmospheric pressure threshold is programmed.
The following rule applies:
Atmospheric pressure
× N
Atmospheric pressure threshold = —————————————
100
Where:
Atmospheric pres-
sure threshold [mbar] : If the pressure inside the vacuum chamber rises
above this threshold, the relay "Atmosheric pres-
sure reached" is energized.
Atmospheric
pressure [mbar] : Atmospheric pressure (100%, ambient) 1)
N [%] : "Percentage of Atmosphere"
(1 … 140%, default value = 5%)
(Example values in the diagram below are printed in italic)
M
ea
su
re
d
va
lue
Measuring signal
(Pressure p)
833 mbar
816 mbar
1500 mbar
980 mbar
Atmospheric pressure (100%, ambient)
"Percentage of Atmosphere"
(85%)
(Atmospheric pressure
threshold)
Hysteresis
(2% of atmospheric
pressure threshold)
Relay status "Atmospheric pressure reached"
Upper limit of measuring range of gauge
1)
1)
The (piezo) sensor measuring atmospheric pressure can be
calibrated to the value of the Capacitance Diaphragm Gauge pressure
(
→ 25).
Setpoint function
"
Atmosphere Control"