ISOLATION FOR SIGNAL AMPLIFIER

Discussion in 'General Electronics Chat' started by viju, May 1, 2009.

  1. viju

    Thread Starter Senior Member

    Sep 28, 2008
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    How to isolate the signal amplifier i.e from the sensor to the measuring circuit? I found in the internet ISO 122, ISO 124 solve this purpose.

    How to connect this isolation amplifier? Do I need to connect at the amplifier input or at the output of amplifier?
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    I have used the ISO 122 - works fine.

    The only problem is that you need two power supplies - one isolated.

    I used a small isolated (1W) DC-DC dual output (+/- 15V) converter module for the isolated side DC supply. They aren't cheap!
     
  4. viju

    Thread Starter Senior Member

    Sep 28, 2008
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    I have decided to use two power supplies.But how to interface? I have decided to use this IC for gain amplifier ( 1:100). Should I have to feed signal into the IC or output of the amplifier to be connected to the IC?
    Pls guide.
     
  5. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    The ISO122 has unity gain so if you require 100x gain you need to decide on which side of the isolation barrier you want to do the amplification.

    If you have a very low input signal which is subject to noise &/or sitting at an unusual common mode level, you might consider running a differential input stage with the 100x gain before going to isolation. You can use your isolated power source to run this as well.

    See this link for a typical diff amp.

    http://focus.ti.com/lit/ds/symlink/ina111.pdf

    You can buy complete single power supply isolation modules with gain but they can get quite expensive.
     
  6. viju

    Thread Starter Senior Member

    Sep 28, 2008
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    Thankyou very much for the information T N K.I have built the application and it's working fine.
     
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