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DeltaV IMan according to noise frequency range 2K-20Khz.

Iman test-2024-12-16-r1.pdf

Dear Sirs,

Please find the attached file for reference.

We are currently experiencing high-frequency noise in the range of 2 kHz to 20 kHz, which is causing interference and resulting in DeltaV AO IMAN and HART communication errors. Additionally, AMS is unable to detect the instruments.

Could you please assist us in resolving this issue?

Thank you for your support.

Best regards,
Lin Chun Hung

ChunHung Lin
  • Jonas Berge

    HART uses 1.2/2.2 kHz so any noise in the 500 Hz to 10 kHz range will interfere with HART communication.

    You will have to find a way to get rid of the noise. If there is a problem with the cable shield or device grounding it will not do a good job rejecting noise.

    Any changes to the device or wiring caused this?

    The source of high frequency noise is usually variable speed drives (variable frequency drives) or UV lamps

    See pointers for troubleshooting in this essay. Search for the word ‘noise’.

  • ChunHung Lin
    Hi Jonas,
     
    Thank you for your advice.
     
    We understand that the noise originates from the VFD and that it can disrupt HART communication.
    However, we are trying to understand why this noise also affects IMan, causing the DCS to lose control.
    While it is acceptable for AMS/DM to be affected, the impact on IMan is a major concern, especially since the noise in question is only around 15 kHz.
    This has led the customer to question whether DeltaV has sufficient resistance to noise interference.
     
    Do you have any solutions to address this issue besides adding a 250-ohm resistor?
    As shown in the attached file, adding the resistor seems to restore the HART waveform, though we are not certain why it works.
    Unfortunately, using ferrite beads has not been effective in resolving the issue.
     
    Your insights and recommendations would be greatly appreciated.
    Thank you for your support.
     
    Best regards,
    Lin Chun Hung
  • Andre Dicaire

    In reply to ChunHung Lin:

    The HART channels have the HART_ERRORS parameters that pass HART status information to the channel status. When HART communications are lost, this can cause the IO CHANNEL to indicate Bad Status and that drives the AO to IMAN.

    You can set the channels to ignore HART status. That does not solve the loss of HART due to noise, but could mitigate the consequence to control.

    I don't see an attached file so I'm not sure how you connected the 250 ohm resistor and what signal this was done on. If put in series with a DVC, I expect the added loop resistance increases the HART signal amplitude above the noise so that it is seen by the AO channel.

    Andre Dicaire

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