Technical data of CPU 31xC 
  6.6 Technical data of the integrated I/O 
CPU 31xC and CPU 31x, Technical Data 
Manual, 01/2006 Edition, A5E00105475-06 
6-49 
6.6.8  Analog inputs 
Introduction 
This chapter contains the specifications for analog outputs of CPUs 31xC. 
The table includes the following CPUs: 
•  CPU 313C 
•  CPU 314C-2 DP 
•  CPU 314C-2 PtP 
Technical data 
Table 6-14  Technical data of analog inputs 
Technical data 
Module-specific data 
Number of inputs  4 channels with current/voltage input 
1 channel with resistance input 
Cable length   
•  Shielded 
Max. 100 m 
Voltage, currents, potentials 
Resistance input   
•  No-load voltage 
Typically 2.5 V 
•  Measurement current 
Typically 1.8 mA to 3.3 mA 
Electrical isolation   
•  Between channels and the backplane bus 
Yes 
•  Between the channels 
No 
Permitted potential difference   
•  Between inputs (AI
C
) and M
ANA
 (U
CM
) 
8.0 VDC 
•  between M
ANA
 and M
internal
 (U
ISO
) 
75 VDC / 60 VAC 
Insulation test voltage  600 VDC 
Analog value generation 
Measurement principle  Actual value encoding (successive 
approximation) 
Integration time/conversion time/resolution (per channel)   
•  Configurable 
Yes 
•  Integration time in ms 
2,5 / 16,6 / 20 
•  Permitted input frequency 
Max. 400 Hz 
•  Resolution (including overdrive) 
11 bits + signed bit 
•  Suppression of interference frequency f1 
400 / 60 / 50 Hz 
Time constant of the input filter  0,38 ms 
Basic processing time  1 ms