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Open collector Passive output on Oscilloscope

Discussion in 'General Electronics Discussion' started by Naseem, May 1, 2018.

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  1. Naseem


    May 1, 2018
    Hi everyone,

    I am trying to display the pulse output on a oscilloscope, which is open collector configured. HART communication is used.

    The output pin no. Of the sensor are +24 and -25. Initially I connected the Oscilloscope directly to the output terminals and was unable to see any pulse on Oscilloscope. Then realised about pull up resistor.

    Now, I have a doubt that should the provide a external supply voltage to see the output pulses?? I am also worried if the device may get damaged due to the external supply.

    The specs of this terminal is as file attached below.

    I just want to make sure, if I am connecting it right??

    Thanks in advance

    Best Regards

    Attached Files:

  2. kellys_eye


    Jun 25, 2010
    The whole purpose behind an open collector output is to allow the user to connect whatever supply/load arrangement they need to suit their requirements - within the limitation of the open-collector transistor parameters of course.

    Your version is totally passive i.e. the output transistor has neither a supply/load (via the collector) nor an earth (via the emitter) connection so these both have to be established externally for the output to work.

    The examples for connection are shown in the document you posted are there for reference and all the information you need.
  3. Naseem


    May 1, 2018
    Thanks a lot for your reply.
  4. Naseem


    May 1, 2018
    I ll try out the connection as shown in the PDF. Once again thanks a ton.
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