Siemens SIMATIC S5-115F, User Manual

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S5-115F Manual Analog Value Processing
Wire-break message for resistance thermometers
A break in the instrument leads to a resistance thermometer is indicated as shown in Table 6-13.
Table 6-13. Wire-Break Message for Resistance Thermometers
Wire-Break at M+ M -
PT 100
(Resist. Sensor)
S+ S -
Digital analog
value
0 0 0 0 0
Status of the
error bit
*
1 1 1 0 1
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* The 460 analog input module encodes the value 0 for unbroken PT 100 resistors and sets error bit F = 0.
If you have chosen the ”No wire-break message” function on the module, an interruption in the
leads to the resistance thermometer is flagged by overflow. The overflow bit remains set about
1.5 sec. (OV = 1). In cyclic operation, all other measuring points also flag overflow (OV = 1). The
situation is the same for single sampling if the interval between two codings 1.5 sec.
Wire-break signalling in the case of the 463 analog input module
The 463 analog input module has no hardware wire-break monitoring facility. Use the life zero
measuring range 4 to 20 mA or the software wire-break monitor in FB 250 ANEI:
For this purpose, a wire-break range in the standardized value range must be defined with the
ODGR and UDGR parameters.
The error bit ”FB” is set in FB 250 in the following cases:
•
If the analog value lies within the limits ODGR and UDGR
• If the DRAK bit is set in the control program ( 6.9).
Note
If you use a 4-wire transducer at analog inputs with measuring range 4 to 20 mA, the
sensors must already be supplied when the PLC starts up. Otherwise the system
responds with a wire-break signal.
EWA 4NEB 811 6148-02
6-27