Temperature sensing

Discussion in 'The Projects Forum' started by perzade, Apr 5, 2012.

  1. perzade

    Thread Starter New Member

    Jan 30, 2011
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    I'm having problem in biasing the LM35 temperature IC. The multimeter reads 0.6v for a bias of 5v & output is also erroneous.Is there any proper biasing circuit for the IC or a direct supply of 5v will work???
     
  2. #12

    Expert

    Nov 30, 2010
    16,302
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    Judging from your schematic, I'd say just give the LM35 five volts and let it output what it wants to output.
     
  3. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I don't see a schematic, however the LM35 requires no special "biasing." It operates on 4-30 volts, and its output is independent of the input voltage within that range. The output is a linear function of the temperature sensed by the LM35.
     
  4. #12

    Expert

    Nov 30, 2010
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    I don't see a schematic either. I was trying to get perzade to post one.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    A picture might be even better. Like anything with 3 pins, it's easy to get them out of order. Been there, done it. Amazingly, the LM35 can survive a mistake at 5V, but not more. I suggest double checking the pinout. Also, the output really should be shown a small load, and a meter may not be enough.
     
  6. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    Its simple apply regulated +5 volt dc to pin 1 and connect pin 3 to GND and read the voltage between pin 2 and GND.

    If you don't get a proper out put then most probably the IC is damaged,for proper pin out check the datasheet.

    Good Luck
     
  7. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    Remember the output scale factor for LM35 is about 20mV/C i.e.. 20 milli volt per degree centigrade (Celsius).So if the temperature is 30 degree centigrade then the output will be 30 * 20 = 600mV i.e.. 0.6V as your meter is showing.

    Good Luck
     
  8. wayneh

    Expert

    Sep 9, 2010
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    Ummm.... Pretty sure it's 10mV per °C, not 20
     
  9. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    Sorry ,yes its 10mV,I was thinking about LM37 which I work with most...
     
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