Siemens SIMATIC ET 200AL, System Manual

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What you should know about analog technology
2.5 Linearity errors
Analog value processing
Function Manual, 06/2014, A5E03461439-AC
21
2.5 Linearity errors
Definition
Linearity denotes the deviation of the actual A/D or D/A conversion from the ideal lines within
a specified measuring range. The linearity error therefore represents the deviation of the real
transmission function from the ideal straight line. The error is given in the technical data as a
percentage of the rated range of the analog module.
The figure below shows the linearity error of an ADC, magnified for better visibility.
Figure 2-11 Linearity errors
Example
An error of ±1 mV is returned at an input range of ±10 V and a linearity error of ±0.01%. The
error is calculated as follows: 10 V · 0.01 % = 1 mV
The linearity error information given in the technical specifications is taken into account in the
operational limit. You will find a detailed description of the operational limit in Operational
and basic error limits (Page 23).