Siemens SIMATIC S7 System Manual page 713

Type Under-range
minimum
TXK/XK(L) -200.0°C
Voltage -32512
Thermocouple values below the under-range minimum value are reported as -32768.
1
Thermocouple values above the over-range minimum value are reported as 32767.
2
Internal cold junction error is ±1.5°C for all ranges. This adds to the error in this table. The module requires at least 30
3
minutes of warmup time to meet this specification.
In the presence of radiated radio frequency of 970 MHz to 990 MHz, the accuracy of the SM 1231 AI 4 x 16 bit TC may
4
be degraded.
Table A- 98 Noise reduction and update times for the SM 1231 Thermocouple
Rejection frequency selection
400 Hz (2.5 ms)
60 Hz (16.6 ms)
50 Hz (20 ms)
10 Hz (100 ms)
To maintain module resolution and accuracy when 400 Hz rejection is selected, the integration time is 10 ms. This
1
selection also rejects 100 Hz and 200 Hz noise.
It is recommended for measuring thermocouples that a 100 ms integration time be used. The
use of smaller integration times will increase the repeatability error of the temperature
readings.
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 that 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 of the module in your configuration. If required, you can
include logic in your user program to accommodate the initialization time of the module.
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
Nominal range
low limit
1
-150.0°C
-27648
-80mV
Integration time
10 ms
1
16.67 ms
20 ms
100 ms
A.7 Thermocouple and RTD signal modules (SMs)
Nominal range Over-range
high limit maximum
800.0°C 1050.0°C
27648 32511
80mV
4 Channel module update
time (seconds)
0.143
0.223
0.263
1.225
553BTechnical specifications
Normal range
3, 4
accuracy @ 25°C
2
±0.6°C
±0.05%
8 Channel module update
time (seconds)
Normal range
1, 2
accuracy
0°C to 55°C
±1.2°C
±0.1%
0.285
0.445
0.525
2.450
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