Siemens CP 1243-7 LTE Operating Instructions Manual page 98

Configuration
4.12 Data point configuration
Set limit value 'low' / Set limit value 'high'
Requirements for the function
● Configuration of the threshold trigger for this data point
● PLC tag in the bit memory operand area or data area
The analog value data point must be linked to a PLC tag in the bit memory or data area
(data block). For PLC tags of hardware modules (input operand area) limit value
configuration is not possible.
The configuration of limit values is pointless for measured values that have already been
preprocessed on the CPU.
Function
In these two input boxes, you can set a limit value in the direction of the start of the
measuring range or in the direction of the end of the measuring range. You can also
evaluate the limit values, for example as the start or end of the measuring range.
Status identifier "OVER_RANGE" / "overflow"
With protocols that support status identifiers, if the limit value is overshot or undershot, the
status identifier of the data point is set for measured range violation indicated below as the
identifier "OV". This status identifiers are described in the section Status IDs of data points
(Page 87).
The "OV" bit of the status identifier of the data point is set as follows when the relevant
analog value is transferred:
● Limit value 'high':
– If the limit value is exceeded: OV = 1
– If the value then falls below the limit value: OV = 0
● Limit value 'low':
– If the value falls below the limit value: OV = 1
– If the value then exceeds the limit value: OV = 0
Configuration of the limit value
The limit value is configured as a whole decimal number. The range of values is based on
the range of values of the raw value of analog input modules.
Range
Overflow
Overrange
Nominal range
(unipolar / life zero)
98
Raw value (16 bits) of the PLC tag
Decimal Hexadecimal
32767 7FFF
32511 7EFF
...
27649 6C01
27648 6C00
...
0 0000
Module output [mA]
0 .. 20
(unipolar)
> 23.515
23.515
... ...
20.001
20
... ...
0
Operating Instructions, 04/2017, C79000-G8976-C381-03
-20 .. +20 4 .. 20
(bipolar) (life zero)
> 23.515 > 22.810
23.515 22.810
... ...
20.001 20.001
20
...
4
CP 1243-7 LTE
Measuring
range [%]
> 117.593
117.593
...
100.004
100
...
0