Siemens SIMATIC ET 200AL, System Manual

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Parameters/address space
4.3 Explanation of the parameters
Analog input module AI 4xRTD/TC 4xM12 (6ES7144-5KD50-0BA0)
Equipment Manual, 08/2021, A5E48753535-AB
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Smoothing
The purpose of smoothing is to filter out interferences. The greater the smoothing factor, the
better the filter effect. This is technically implemented in the form of a digital filter. The
smoothing can be set in 4 levels. The smoothing factor k is equal to the number of module
cycles. The time constant of the smoothing filter is the product of the smoothing factor k and
the cycle time of the I/O module. The greater the smoothing, the greater the time constant of
the filter.
Smoothing time = number of module cycles (k) × cycle time of the module.
The following figure shows how many module cycles it takes for the smoothed analog value
to approach 100%, depending on the configured smoothing. This is valid for all signal
changes at the analog input.
① No smoothing (k = 1)
② Weak (k = 4)
③ Medium (k = 16)
④ Strong (k = 32)
Figure 4-1 Smoothing
Interference frequency suppression
This parameter suppresses interference for analog input modules which is caused by the
frequency of the alternating voltage network in use.
The frequency of the alternating voltage network may negatively affect the measured value,
in particular when measuring in the low voltage range and with thermocouples. With this
parameter, the user specifies the line frequency that is predominant in the plant.
Diagnostics: Reference junction
Enabling of the reference junction diagnostics if the reference temperature of the reference
junction needs to be determined for the TC channel being operated.