Siemens S7-1200 - Page 924

Technical specifications
A.9 Thermocouple and RTD signal modules (SMs)
S7-1200 Programmable controller
924 System Manual, 03/2014, A5E02486680-AG
Table A- 170 Noise reduction and update times for the SM 1231 Thermocouple
Rejection frequency selection
Integration time
4 Channel module update
time (seconds)
8 Channel module update
time (seconds)
400 Hz (2.5 ms)
10 ms
1
0.143
0.285
60 Hz (16.6 ms)
16.67 ms
0.223
0.445
50 Hz (20 ms)
20 ms
0.263
0.525
10 Hz (100 ms)
100 ms
1.225
2.450
1
To maintain module resolution and accuracy when 400 Hz rejection is selected, the integration time is 10 ms. This
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. You
r 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.
Representation of analog values for Thermocouple Type J
A representation of the analog values of thermocouples type J is shown in the table below.
Table A- 171 Representation of analog values of thermocouples type J
Type J in °C
Units
Type J in °F
Units
Range
Decimal
Hexadecimal
Decimal
Hexadecimal
> 1450.0
32767
7FFF
> 2642.0
32767
7FFF
Overflow
1450.0
:
1200.1
14500
:
12001
38A4
:
2EE1
2642.0
:
2192.2
26420
:
21922
6734
:
55A2
Overrange
1200.0
:
-150.0
12000
:
-1500
2EE0
:
FA24
2192.0
:
-238.0
21920
:
-2380
55A0
:
F6B4
Rated range
< -150.0
-32768
8000
< -238.0
-32768
8000
Underflow
1
1
Faulty wiring (for example, polarity reversal, or open inputs) or sensor error in the negative
range (for example, wrong type of thermocouple) may cause the thermocouple module to
signal underflow.