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Tank resonance locator

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Vijit Dubey, Sep 21, 2015.

  1. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Use an LM35
     
  2. Vijit Dubey

    Vijit Dubey Member

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    reading the datasheet. Give me some time.
     
  3. Vijit Dubey

    Vijit Dubey Member

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    Isn't this like a thermometer. I mean it would read the ambient temperature but I want to use the thermistor embedded inside the IGBT. I think LM35 defeats my purpose.
     
  4. dave

    Dave New Member

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  5. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Inside as in a Hybrid array like Mitsubishi's IGBT 1 Gigawatt switches.

    Diodes are linear, Thermistors are not unless properly designed in a CC array,

    Consider a signal diode then. just like CPU's do.

    LM35's are very linear.
     
  6. Vijit Dubey

    Vijit Dubey Member

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    I know the graph is logarithmic. I just want to monitor if the temperature goes beyond a certain point. So, the moment it goes beyond a certain frequency I need an alarm.
     
  7. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Sorry I lost track of your design for these measurements.

    I cant see the scope of the project and why you chose v to f then f to v to detect an alarm condition. Certain EMI issues of ingress must be corrected.
     
    Last edited: Nov 6, 2015
  8. Vijit Dubey

    Vijit Dubey Member

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    I didn't follow what you meant by v to f and f to v.
    I will be monitoring digital input 1 to know the switching rate and know which IGBT thermistor I am on right now(to know which PLC am I on right now). I'll be using digital input 2 to measure the frequency (as R changes) and measure temperature if it goes beyond a certain limit.

    How can I filter the EMI?
     
  9. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    I cant see your system design, but low impedance analog might be easier and faster to commutate than a thermistor controlled frequency (V to F or rather R to F)
     
  10. Vijit Dubey

    Vijit Dubey Member

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    The concern with analog (voltage) is that if any IGBTs blow. Previously, I was using a voltage bridge. How do I isolate and make sure they don't blow other IGBTs aor PLC.

    PS2501-4 will give me isolation upto 5KV rms.

    This is the attachement of schematic for board.
     

    Attached Files:

    Last edited: Nov 6, 2015
  11. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    I might recommend Mitsubishi J-Series T-PM IGBT, diode integrated on IGBT chip is used to detect chip temperature directly and enable to turn off IGBT safely and fast for over-temperature protection. But I dont know if that meets your requirements.
     
  12. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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