S7-200 Specifications
A-73
S7-200 Programmable Controller System Manual
A5E00066097-02
Using the Thermocouple: Status Indicators
The thermocouple module provides the PLC with data words that indicate
temperatures or error conditions. Status bits indicate range error and user
supply/module failure. LEDs indicate the status of the module. Your program
should have logic to detect error conditions and respond appropriately for the
application. Table A-27 shows the thermocouple status indicators.
Table A-27 Thermocouple Status Indicators
Error Condition
Channel Data SF LED 24 V LED
Range Status
Bit
1
24 V Module
Bad Status Bit
2
No errors Conversion
data
OFF ON 0 0
24V missing 32766 OFF OFF 0 1
Open wire and
current source
enabled
-32768/32767 BLINK ON 1 0
Out of range
input
-32768/32767 BLINK ON 1 0
Diagnostic error
3
0000 ON OFF 0 *
1
Range status bit is bit 3 in module error register byte (SMB9 for Module 1, SMB11 for Module 2, etc.)
2
Bad status bit is bit 2 in module error register byte (SMB 9, SMB 11, etc. Refer to Appendix C.)
3
Diagnostic errors cause a module configuration error. The module bad status bit may or may not be set
before the module configuration error.
Note
The channel data format is 2’s complement, 16-bit words. Temperature is
presented in 0.1 degree units. (For example, if the measured temperature is
100.2 degrees, the reported data is 1002.) Voltage data are scaled to 27648. For
example, -60.0mV is reported as -20736 (=-60mV/80mV * 27648).
All four channels are updated every 405 milliseconds if the PLC has read the data.
If the PLC does not read the data within one update time, the module reports old
data until the next module update after the PLC read. To keep channel data
current, it is recommended that the PLC program read data at least as often as the
module update rate.
Note
When you are using the thermocouple module, you need to disable analog
filtering in the PLC. Analog filtering can prevent error conditions from being
detected in a timely manner.
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