Siemens 181 Workshop Manual page 16

Special features when using PTC resistors
PTCs are suitable for monitoring temperature and/or as thermal protection devices of
complex drives or transformer windings.
● Choose "Thermal resistor (2-wire)" and "PTC" in the parameter assignment.
● Connect the PTC to the 2-wire connection technology.
● Use the PTC resistors, type A (PTC thermistor) in accordance with DIN/VDE 0660,
● If "Underflow" diagnostic is enabled, a "Low limit violated" diagnostic is generated for
● Sensor data for the PTC resistor:
Table 4- 2
Switching points
(RRT-5) °C
(RRT+5) °C
(RRT+15) °C
Measuring voltage/
voltage at the PTC
1
Analog input module AI 4xRTD/TC 2-/3-/4-wire HF (6ES7134-6JD00-0CA1)
Manual, 02/2014, A5E03573289-AD
part 302.
resistance values < 18 Ω, indicating a short-circuit.
Using PTC resistors
Property
specifications
Behavior with rising temperature
< 550 Ω
550 Ω to 1650 Ω
> 1650 Ω
Behavior with falling temperature
> 750 Ω
750 Ω to 540 Ω
< 540 Ω
Reaction to short-circuit
< 18 Ω
Max. 550 Ω
min. 1330 Ω
min. 4000 Ω
Max. 7.5 V
Below 23 kΩ
4.1 Measurement types and measuring ranges
Technical
Normal range:
SIMATIC S7: Bit 0 = "0", Bit 2 = "0" (in the PII)
•
Prewarning range:
SIMATIC S7: Bit 0 = "0", Bit 2 = "1" (in the PII)
•
Response range:
SIMATIC S7: Bit 0 = "1", Bit 2 = "0" (in the PII)
•
Response range:
SIMATIC S7: Bit 0 = "1", Bit 2 = "0" (in the PII)
•
Prewarning range:
SIMATIC S7: Bit 0 = "0", Bit 2 = "1" (in the PII)
•
Normal range:
SIMATIC S7: Bit 0 = "0", Bit 2 = "0" (in the PII)
•
SIMATIC S7: Bit 7 (IB x+1) = "1", Bit 0 = "0" and
•
Bit 2 = "0"
TNF = Rated response temperature of the sensor
(according to DIN/VDE 0660)
1
Parameters/address space
Comment
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