Connect with us

Diode - Temperature

Discussion in 'General Electronics Discussion' started by M.Sridhar, Oct 2, 2015.

Scroll to continue with content
  1. M.Sridhar

    M.Sridhar

    10
    0
    Sep 16, 2015
    How to measure temperature using diode.Can it be used in such a way?
     
  2. ed181

    ed181

    15
    0
    Dec 27, 2010
    Why would you want to measure temperature using a diode?
     
  3. ed181

    ed181

    15
    0
    Dec 27, 2010
    You can but it looks like a lot of work and it won't be accurate
     
  4. Old Steve

    Old Steve

    734
    169
    Jul 23, 2015
  5. Arouse1973

    Arouse1973 Adam

    5,164
    1,080
    Dec 18, 2013
    Yes it can. A common method is to use a transistors base emitter diode. Simply pass a constant current through the transistor configured as a transdiode. Have another reference like a potential divider also with a constant current passing through it. Connect this to a comparator and calibrate for use. As the temperature changes the transdiode voltage will change and this can be sensed by the comparator.
    Thanks
    Adam
     
  6. Alec_t

    Alec_t

    2,822
    754
    Jul 7, 2015
    The junction voltage of a diode changes by about -2mV per deg C rise, but if you want to experiment you can use the base-emitter junction of a transistor in an 'amplified-diode' configuration as shown in the attachment, to give a greater change.
    AmplifiedDiode.PNG
    This behaves like a diode with a 0.6V junction voltage multiplied by approximately (1 + R1/R2), and a correspondingly multiplied change with temperature.
     
  7. Arouse1973

    Arouse1973 Adam

    5,164
    1,080
    Dec 18, 2013
    The BE junction of a transistor changes by the same amount. They are all PN junctions.
    Thanks
     
  8. Alec_t

    Alec_t

    2,822
    754
    Jul 7, 2015
    Correct. The 'amplified diode' voltage appears between the collector and emitter terminals in the circuit shown.
     
  9. AnalogKid

    AnalogKid

    2,359
    659
    Jun 10, 2015
    Check with Linear Technology, Maxim, Analog Devices. Somebody out there has a chip that uses a diode as a temperature sensor and turns it into either a thermometer or a thermostat.

    ak
     
  10. Arouse1973

    Arouse1973 Adam

    5,164
    1,080
    Dec 18, 2013
    I put my money on Maxim :)
     
  11. Old Steve

    Old Steve

    734
    169
    Jul 23, 2015
    I'd prefer to just use an LM335Z.
     
    Arouse1973 likes this.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-