Interference Voltage Suppression - Siemens SIMATIC ET 200AL System Manual

What you should know about analog technology

2.12 Interference voltage suppression

2.12 Interference voltage suppression
Definition
Interference voltage suppression gives the factor by which the interference signal is
suppressed in measurement value acquisition. Higher values reduce the effect of
interference on the measurement signal. The technical data differentiates between "Common
mode interference" and "Series mode interference". Interference voltage suppression is
specified in decibels.
Example
The diagram below shows the measuring error for interference voltages in volts and
interference voltage suppression of 0 to 120 dB.
Figure 2-17
With an interference voltage suppression of 40 dB and an interference voltage of 1 V, the
measured value is only distorted by 0.01 V.
Note
Interference-free design
Disturbance variables can be substantially reduced by means of appropriate grounding and
shielding to increase interference immunity of the configuration. You will find a detailed
description of how to avoid interference in the Configuring interference-free controllers
(http://support.automation.siemens.com/WW/view/en/59193566) function manual.
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Interference voltage suppression
Analog value processing
Function Manual, 06/2014, A5E03461439-AC