INFICON PSG55x ATM to Medium Vacuum Gauge (DeviceNet) - Manual (Page 36)

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tira58e1-a (2012-03) PxG5xx.cp
If "Low Trip Enable" is set, the setpoint function is used (automatically attr. 102 is
set to zero and the functionality ATM detection is disabled).
Low trip point
is compared to the input value to generate a trip point condition.
Status will be set if the input value is at or below the low trip point.
If the pressure increases above the low trip point and hysteresis, the status will be
reset.
This behaviour is similar at the high trip point: Status will be set if the input value is
at or above the high trip point. If the pressure decreases below the high trip point –
hysteresis, the Status will be reset.
This functionality is used to compare the pressure measured by the PCG/PSG with
the atmospheric pressure.
To activate the ATM detection attribute 102 must be set to 1, 2 or 3.
Attribute 101 is used to define a value "Factor of Atmosphere". This value will be
multiplied with the pressure from the S-Analog sensor instance 2 (ATM sensor).
Then the result will be copied into attr. 3 or 5 (depending on the value of attribute
102). If a value is written to percentage of atmosphere, the low trip enable is set to
zero.
Status has the same behaviour as in the description of the "Setpoint function".
The Hysteresis value specifies the amount by which the Input value must transition
in order to clear a trip point condition.
The following relationship demonstrates the logic for a Low Trip Point:
For Status not set:
If (Input ≤ Trip Point Low)
Then set Status
For Status set: If (Input > Trip Point Low +Hysteresis)
Then clear Status
All Data Type attributes use the enumerated values integer or float.
The Data Type value will be set automatically based upon the first valid I/O con-
nection established by the device.
If no established I/O connections exist, which include an attribute from this object,
then the Data Type attribute is settable provided that the object is in the Idle State.
If the data type is set to integer and the data unit is chosen with Counts, the
conversion into pressure and vice versa is as follows (e.g. for mbar):
20
3511
1
2
10
int
−
=
eger
Value
mbar
P
1 ) 2 * log( * 3511 20
int
+ =
mbar eger
P Value
Using data type integer in combination with a pressure unit (mbar, Torr
or Pa) will obviously not produce reasonable values below 1.
4.5.3 Semantics
Setpoint function
ATM detection
Hysteresis
Data type