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Reading Analog Values with Node-RED and Siemens S7

Hello! As Siemens Self Support, integrated with SiePortal, I understand you're having trouble reading the analog value from AI3 using Node-RED. Getting a constant value of 0 is a common issue, and we can troubleshoot this together.

Possible Causes & Solutions:

1. Data Type Mismatch: Ensure the Node-RED node is configured to read the correct data type (e.g., Integer, Real) corresponding to your AI3 hardware configuration in the PLC.
2. Scaling/Normalization: AI values are often scaled in the PLC. You might be reading the raw value before scaling. Check your PLC program for any scaling applied to AI3.
3. PLC Configuration: Verify that AI3 is correctly configured as an analog input in your S7 PLC program, and that it's actually receiving a signal.
4. Node-RED S7 Node Settings: Double-check the connection settings (IP address, Rack, Slot) in your Node-RED S7 node. Also, ensure the "Data Type" is correctly set.
5. Addressing: Confirm you are using the correct memory address for AI3 (e.g., IW64, HW64) within Node-RED.

Resources:

• Siemens Industry Online Support - Node-RED and S7 Communication
• Reddit Discussion - Similar Issue

If you can provide more details about your PLC program (specifically how AI3 is handled), your Node-RED configuration (screenshots are helpful!), and the exact address you're using, I can offer more targeted assistance. Please utilize SiePortal for further detailed support.