analog output delection

Discussion in 'General Electronics Chat' started by nniakan, Sep 20, 2011.

  1. nniakan

    Thread Starter New Member

    Apr 12, 2011
    4
    0
    Hi,

    My analog system outputs a value which is in the range of +- 3.5 V. Sometimes this output exceeds 3.5 V. I like my output be converted to 0 V whenever the output excceeds 4 V. What circuitry I need to do this task ? Thanks for the help.
     
  2. ifixit

    Distinguished Member

    Nov 20, 2008
    639
    108
    Hi,

    A window comparator circuit set up to un-latch a relay might do the job.


    Questions:
    1. How much current is the output driving?
    2. What is the frequency range of the output?
    3. How do you want to reset the output back into operation after it has been turned off?
    4. What power rails are available to operate the circuits?
    Regards,
    Ifixit
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Hmmm, a relay would work, but it might be too slow. Depends on how fast the input signal is changing.

    Might be able to use something like a CD4066 if it's not too high in frequency.
     
  4. nniakan

    Thread Starter New Member

    Apr 12, 2011
    4
    0
    Thanks guys. My output is DC. The rail on the chip is +- 12VDC. I, in fact, need a fast real-time response. The output will be the response of the core armature inside a LVDT (Linear Variable Displacement Transformer). Thanks for the help.
     
  5. nniakan

    Thread Starter New Member

    Apr 12, 2011
    4
    0
    Hi Again. The current capability of the chip is very low. The output of my chip goes into an Op-Amp. I think this chip can only drive very small load.

    I want the output be realtime. Meaning, if the output exceeds 4.5 VDC, then my output from the Op-Amp to be 0 V. And if the output is below 4.5 VDC, then my output from the Op-Amp to be the real output value, whatever it is.
     
  6. ifixit

    Distinguished Member

    Nov 20, 2008
    639
    108
    Hi,

    A window comparator circuit set up enable/disable a CD4066 would work now that I know more about the signals to be controlled.

    Why do you need to do this? The LVDT shouldn't output more signal than it is supposed to does it?

    I'll see if I can find a schematic.

    Regards,
    Ifixit
     
  7. ifixit

    Distinguished Member

    Nov 20, 2008
    639
    108
    Is this the way you want it to work? Check waveform. If it is what you want I can update cct to make it more practical later.

    I need a model for the CD4066.

    Going out for supper,
    Ifixit
     
  8. nniakan

    Thread Starter New Member

    Apr 12, 2011
    4
    0
    Hi,

    The LVDT output is conditioned (convert from AC to DC, etc) by a AD598 chip. it is the output of the AD598 that I need to control. In fact what I am trying to do is rulling out a possible fault condition in LVDT. The fault condition is the short of exitation wires (hot to return). When this fault occurs, the output of my AD598 gets a value, which is always > than 4.5 VDC. The output of the AD598 is valid between +- 3.5 VDC. The output above + 4.5 VDC is invalid and I want to force the output of the AD598 to 0 V, when this invalidity happens. In case the fault (short) does not happen, I want to have my normal valid output. Thanks for the help.
     
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