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Asked:18 Oct 2025

SIMATIC S7-300 / S7-300F: 6ES7 331-1KF01.. och Pt100 problems..

Hello
Having an AI-Card (6ES7331-1KF01)config for 4-20mA.
Have connected an PT100 with converter (0-100C->4-20mA)
Feeds the PT100 with 24V+ and the value from PT100 to I+ (ch 2 (12)). Then M- to 0V (ch 2 (15)).
The messuringvalue is aprox. 10C* higher than it should be, when i connect an simulator on the card it seems to be OK, there must be som kind of missmatch. the powerunit is grounded on the M-. Any idé???
Hej
Har kopplat in en PT100 givare med omvandlare i huvudet 0-100->4-20mA.
Problemet är att jag ligger cirka 10 grader över vad jag borde.
Har kopplat +24V ut till givaren, svaret tillbaka in på I+ samt minus på M- (ch 2 Uttag 12 och 15).
Simulerar jag direkt på kortet verkar det stämma linjärt, någon idé.

#sosflex #SIMATIC S7-300 / S7-300F #siemens
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Answers(1)
Siemens Test Added an Answer on18 Oct 2025

AI Card (6ES7331-1KF01) - 4-20mA Measurement Issue

It appears you're experiencing a 10°C offset in your PT100 temperature readings when using a 4-20mA converter with the Siemens AI card. The simulator test working correctly suggests a hardware/wiring issue rather than a card malfunction.

Potential Causes & Troubleshooting:

  • Ground Loop: Since your power supply is grounded to M- (channel 2, terminal 15), a ground loop could be introducing a common-mode voltage, causing inaccurate readings. Try isolating the power supply ground.
  • Wiring: Double-check your wiring connections. Ensure I+ (channel 2, terminal 12) and M- (channel 2, terminal 15) are correctly connected to the 4-20mA output of the converter.
  • Converter Offset: Verify the 4-20mA converter's calibration. An offset in the converter itself could explain the consistent error.
  • Cable Shielding: Ensure the cable connecting the PT100 converter to the AI card is shielded and properly grounded at one end (preferably the AI card end) to reduce noise.

Further Support:

For detailed configuration guides and troubleshooting steps, please refer to the SiePortal documentation for the 6ES7331-1KF01 AI card: Siemens Industry Online Support

If the issue persists, consider contacting Siemens Support directly through SiePortal for personalized assistance.

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