Siemens SIMATIC S5 Manual page 207

Blocks
COM 115F is used to configure the analog value representation of the module (channel type).
There are three methods of wire-break detection:
Hardware wire-break detection
This is implemented on the 460 AI module with the 498-1AA11 range card. The condition code
bit F is set in the event of a wire-break and evaluated by FB 250 ANEI.
Wire-break detection by FB 250 ANEI
The 460 AI module with range cards 498-1AA51 or 498-1AA71 and the 463 AI module with the
jumper setting for the range 4 to 20 mA, use the life-zero procedure for wire-break detection:
If the sensors, the signal path and the input module are intact, the smallest permissible value is
4 mA. All values less than 3 mA are interpreted by FB 250 ANEI as wire-break.
Wire-break detection by the user program and FB 250 ANEI
All measuring ranges of both AI modules which do not permit wire-break detection as in
and must use the following procedure supported by the user program.
For this purpose, a wire-break range in the standard value range must be set with the "ODGR"
and "UDGR" parameters of FB 250 ANEI.
The error bit "F" is set in FB 250 if
• the analog value is within the "ODGR" and "UDGR" limits
and
• the "DRAK" bit is set in the control program ( 6.9).
Testing the line for wire-break only makes sense with this procedure if the analog value is
outside the wire-break limits.
6-6
S5-115F Manual
EWA 4NEB 811 6149-02