Siemens SIMATIC ET 200AL, System Manual

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Analog value processing
Function Manual, 06/2014, A5E03461439-AC
5
Table of contents
Preface ................................................................................................................................................... 3
1 Documentation guide .............................................................................................................................. 7
2 What you should know about analog technology ..................................................................................... 9
2.1
Overview ........................................................................................................................................ 9
2.2 Precision/resolution ...................................................................................................................... 13
2.3 Scaling analog values .................................................................................................................. 17
2.4 Unscaling analog values .............................................................................................................. 19
2.5 Linearity errors ............................................................................................................................. 21
2.6 Repeat accuracy .......................................................................................................................... 22
2.7 Operational and basic error limits ................................................................................................ 23
2.8 Temperature error ........................................................................................................................ 26
2.9 Interference frequency suppression............................................................................................. 27
2.10 Common mode interference (UCM) ............................................................................................. 29
2.11 Series mode interference (USM) ................................................................................................. 31
2.12 Interference voltage suppression ................................................................................................. 32
2.13 Crosstalk between channels ........................................................................................................ 34
2.14 Diagnostics ................................................................................................................................... 36
2.15 Value status ................................................................................................................................. 46
2.16 Conversion time of an analog module ......................................................................................... 49
2.17 Cycle time of an analog module................................................................................................... 51
2.18 Settling and response times of analog output modules ............................................................... 52
2.19 Smoothing .................................................................................................................................... 54
2.20 Burden with 2-wire transducers ................................................................................................... 57
3 Representation of analog values ........................................................................................................... 60
3.1
Overview ...................................................................................................................................... 60
3.2 Representation of input ranges .................................................................................................... 62
3.3 Representation of output ranges.................................................................................................. 63