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Industrial galvanic isolation

Paul Atreides
Prodigy 20 points
Hi,

I want to build a controller for a machine with multiple sensors. The sensors are supplied with power either by the controller itself or have their own power supply. I want to galvanic separate the inputs to protect the controller against interference.

Is it enough if I galvanic isolate a common power supply for the sensor interface and the date lines from the rest of the controller, or it is better if each individual input has its own separate galvanic isolated power supply?

I have found an example of this in an application note from TI.
Industrial data-acquisition interfaces with digital isolation.
http://www.ti.com/lit/an/slyt426/slyt426.pdf

Analog Inputs:
2x 4-20 mA
2x PT100

I would be grateful for any help

 

  • 0
    TI__Intellectual 2200 points

    Hi Paul,

    If all your sensor receivers are referred to the same ground, a single isolated power supply should suffice.

    Thomas Kugelstadt who wrote the appnote you are referring to you is currently on travel. I will remind him of your question, and he may have some suggestions.

    Rgds,

    Anant

  • 0
    TI__Mastermind 28265 points

    Paul Atreides ?, also known as Muad'Dib from Dune, the Desert Planet ?

    Well, if the pressure sensors of your thumpers on Dune have large ground potential differences, typically created by the spice worms, then you need to isolate each thumper through an isolation amplifier. The output of each amplifier (after the isolation barrier) can then feed into one multi-channel ADC, which is directly connected to an MCU.

    This is known as channel-to-channel isolation where each sensor needs to have its own isolated supply.

    If your thumpers are close together using one ground potential, then the transducer or sensor outputs can feed directly into an multi-channel ADC without isolation. The actual isolation would then be implemented at the digital interface between ADC and controller.

    The spice must flow.

    Thomas.

  • 0 in reply to Thomas Kugelstadt
    Prodigy 20 points

    Dear Thomas,

    thank you for your reply. Do you have any recommendations for me where I can learn more about industrial interface protection against interferences.


    Best regards,

    Paul

  • 0 in reply to Paul Atreides
    TI__Mastermind 28265 points

    I have written article in Electronic Design Magazine and Planet Analog. Just google my name.

    we have also some information in the files section of the industrial interface forum.

    regards, Thomas