X20 system modules • Analog input modules • X20AI2437
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X20 system User's Manual 3.10
4.3.6.9.6.3 OpenLoopLimit
Names (pChannelName):
OpenLoopLimit_1
OpenLoopLimit_2
The limit value for the respective analog input must be set when open circuit monitoring is enabled and if required
by the configured normalization. If limit value monitoring is active, the corresponding error status is output after a
configured delay when falling below this value. Using a default value of 2000 µA, the following values and formulas
apply to this parameter:
•
Displaying 0..25 mA as 0..25000 : 2000
•
Displaying 0..25 mA as 0..32767 : 2621, limit value = ([µA]*32767)/25000
•
Displaying 4..20 mA as 0..32767 : -4096, limit value = (([µA]*1.31068) - 5242.72)*1.5625
•
Displaying 0..25 mA as 0..65535 : 5243, limit value = ([µA]*65535)/25000
Data type
Values
INT
-32767...32767: Open circuit limit value
UINT
0...65535: Open circuit limit value
4.3.6.9.6.4 PreparationInterval
Names (pChannelName):
PreparationInterval_1
PreparationInterval_2
If the last valid measurement value should be kept when violating the limit value, then PreparationInterval must be
defined. The measurement values continue to be acquired and converted according to the configured I/O update
time. They are then checked and discarded if they do not meet the specifications. When an error does not occur,
therefore, the measurement value acquired two preparation intervals ago is constantly output.
Data type
Values [0.1 ms]
UINT
0…65535
"Application"
for the value being measured (analog)
↓
Condition:
- Conversion interval (ADC) elapsed
"Measurement value memory"
Measurement value (digital)
↓
Condition:
- PreparationInterval elapsed
- Measurement value permissible
"Buffer"
Last valid value
↓
Condition:
- PreparationInterval elapsed
- Measurement value permissible
How it works:
Measured values are converted at the configured conversion rate and saved to measurement value memory.
The current contents of the measurement value memory are checked within the configured interval. If a permis-
sible value is present, then the contents of the buffer memory are passed to output memory and the contents of
the measurement value memory are passed to the buffer.
If the check turns up an impermissible value, then the contents of the measurement value memory are discard-
ed. The copy direction between the output and buffer memory reverses and the last valid value continues to be
output.
Information:
If configured to keep the last valid value, the delay time from measuring to outputting the value
will be at least twice the preparation interval. In the worst case scenario, this can also take twice
the interval time plus the configured ADC conversion rate.
"Output memory"
Next-to-last valid/
displayed value
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