Digital thermometer

Discussion in 'Homework Help' started by JoyAm, Sep 10, 2014.

  1. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    I am supposed to be able to calculate the room temperature using this two diode circuit but i have no idea how, can you give me some hints ?
    thanks in advance
    Screenshot_4.png
     
  2. dalam

    Member

    Aug 9, 2014
    58
    6
    Voltage drop across diodes depends on temperature.
     
    JoyAm likes this.
  3. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    By the factor VT=K*T/q ?
    and i will use this VD=VT*ln(ID/IS)
    in that case idk what the value of IS is
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Not sure that V(x)-V(y) is any better than V(x) or V(y) by itself...


    206.jpg
     
  5. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    The V(x)-V(y) represents the Vp .But well i still dont know how can i solve it
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Start here...

    The simulation shows the temperature dependence of the forward voltage drop of two ideal diodes with different forward currents. Vp = V(x)-V(y)
     
  7. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    T=vp*q/(ln(I1-I2)*k) is that right ?
    Oh i think i got it just give me some minutes
     
  8. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    Or not...
    Vp=(k*T/q)*ln(I1/I2)
    dVp/dT=0.139=(k/q)*ln(I1/I2)
    so from that we can calculate the k/q
    and then i dont know
     
  9. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,962
    1,097
  10. JoyAm

    Thread Starter Member

    Aug 21, 2014
    112
    4
    Screenshot_5.png this looks like what i got on post #7 but still how can i use the gived dvp/dT to solve the problem ?
     
Loading...