Siemens SIMATIC S7 - Page 761

Technical specifications
A.5 Thermocouple and RTD expansion modules (EMs)
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
761
Table A- 128 Resistance
Range
Under range
minimum
Nominal range
low limit
Nominal range
high limit
Over range
maximum
1
Normal range
accuracy @ 25
°C
Normal range
accuracy -20
°C to 60°C
150 Ω
n/a
0 (0 Ω)
27648 (150 Ω)
176.383 Ω
±0.05%
±0.1%
300 Ω n/a 0 (0 Ω) 27648 (300 Ω) 352.767 Ω ±0.05% ±0.1%
600 Ω
n/a
0 (0 Ω)
27648 (600 Ω)
705.534 Ω
±0.05%
±0.1%
1
Resistance values above the over-range minimum value are reported as +32767.
Note
The module reports
32767 on any activated channel with no sensor connected. If open wire
detection is also enabled, the module flashes the appropriate red LEDs.
When 500 Ω and 1000 Ω RTD ranges are used with other lower value resistors, the error
may increase to two times t
he specified error.
Best accuracy will be achieved for the 10 Ω RTD ranges if 4 wire connections are used.
The resistance of the connection wires in 2 wire mode will cause an error in the sensor
reading and therefore accuracy is not guaranteed.
Table A- 129 Noise reduction and update times for the RTD module
Rejection frequency selection
Integration time
Update time (seconds)
400 Hz (2.5 ms) 10 ms
1
4-/2-wire: 0.142
3-wire: 0.285
60 Hz (16.6 ms) 16.67 ms 4-/2-wire: 0.222
3-wire: 0.445
50 Hz (20 ms) 20 ms 4-/2-wire: 0.262
3-wire: .505
10 Hz (100 ms) 100 ms 4-/2-wire: 1.222
3-wire: 2.445
1
To maintain module resolution and accuracy when the 400 Hz filter is selected, the integration time is 10 ms. This selec-
tion also rejects 100 Hz and 200 Hz noise.
Note
After power is applied, the module performs internal calibration for the analog
-to-digital
converter. During this time the module reports a value of 32767 on each channel until valid
data is available on tha
t channel. Your user program may need to allow for this initialization
time. Because the configuration of the module can vary the length of the initialization time,
you should verify the behavior or the module in your configuration. If required, you can
in
clude logic in your user program to accommodate the initialization time of the module.