Siemens Simatic SM331 Getting Started page 32

Interference frequency (Interference frequency suppression)
The frequency of the AC power supply network can interfere with the
measurement values, especially in low voltage ranges and when thermo-
couples are used. With this parameter you specify the frequency of your
power supply on site.
This parameter also influences the granularity, integration time and the ba-
sic execution period of the channel group.
Resolution (Accuracy)
The analog value is stored in a 16-bit word.
Integration time
The module requires a certain amount of time to measure the analog volt-
age. This time is called integration time. The higher the required accuracy
is, the longer the module needs for measuring the voltage.
Basic execution period
Besides the integration time, the module also needs a certain amount of
time to provide the measurement value.
Table 6-2
Resolution
9 Bit
12 Bit
12 Bit
14 Bit
Hardware alarm
Only the channels 0 and 2 have hardware interrupt capabilities. You can
use hardware interrupts to trigger an alarm when the analog signal exceeds
its high or low limit.
Complete the hardware configuration
Close the parameter window.
Compile and save the project via Station # Save and Compile (Ctrl+S)
With this the hardware configuration of the project is completed.
Relationship between accuracy, interference frequency and integration pe-
riod
Interference Integration time
frequency
400 Hz 2,5 ms
60 Hz 16,6 ms
50 Hz 20 ms
10 Hz 100 ms
30 Getting Started SM331 AI 8x12bit Part1: 4-20mA
Basic execution time
24 ms
136 ms
176 ms
816 ms
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