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LM358A: Problem with RF current common mode EN61000-4-6

Jonathan Navor
Genius 9475 points
Part Number: LM358A
Other Parts Discussed in Thread: LM358

Hi Experts,
Good day! I am posting this on behalf of the customer. 

My customer is using your LM358A in a capacity water tank level sensor.
When I'm testing the RF common mode (acc. EN 61000-4-6) the water tank level is not working well: I have a wrong output value and it is not passing the approval limit.
The output is normally at 0V but when I apply the disturbances the value change to 5V.
Could you help me to improve the layout?

In the attached file you have the layout of this water tank level sensor.

Thank you for your help 

Best regards,
Jonathan
 
  • 0
    Guru 140200 points

    Hi Jonathan,

    this is not a failure of LM358 itself but a failure on the whole setup. You must strengthen the setup to be able to comply with the CE standards.

    Put your circuit into a Faraday cage and connect it to signal gound at the cable entry point. Use a shielded cable and connect the shield 360° to the Faraday cage at the cable entry point. Mount pi-filters at the +5Vinput and the signal output and have the filter caps grounds and the signal connected directly to the cable entry point.

    Kai

  • 0 in reply to kai klaas69
    TI__Mastermind 19612 points

    Hey Jonathan, 

    In addition to Kai's comments, if you don't have access to a shielded cable, or if the cable length is really long, I recommend braiding the cables. 
    Also if you have a different op amp, you may test with that to verify if the problem is the system or the device under test. 
    But I agree with Kai, with radiated emissions it is often the setup. 

    All the best,
    Carolina