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  • This digital thermometer circuit diagram uses a common 1N4148 diode as the temperature sensor. The temperature coefficient of the diode, -2 mV/°C is exploited for this application to create an accurate electronic thermometer.
    To display the measured temperature, a digital multimeter is used and so we can measure temperature values from -9.99°C up to +99.9°C.

    Calibration of the digital thermometer

    To set the minimum level (0°C), place the diode in a glass of water filled with crushed ice (check the temperature first with a normal thermometer) wait until the thermometer shows zero degrees centigrade. Set P1 so that the digital voltmeter will display 000 when the diode senses zero degree centigade.
    To set the maximum level (100°C), place the diode sensor into a boiling water and adjust P2 so that the digital meter exactly displays 99.9.

    Schematic of the digital electronic thermometer circuit

    electronic digital thermometer circuit schematic

    For more digital thermometers check related articles.

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    54 Responses to "Diode Digital Thermometer Circuit"

    1. Tamás Tinta says: on October 5, 2009 at 9:55 am

      Digital electronic thermometer circuit diagram is not available in high definition!
      Please send in e-mail me!
      Tamás Tinta

    2. the circuit does not seem to give any results.we have used a 2.2k variable resistance…plz help!

    3. wrong

    4. i hav much more material on this topic

    5. waheed 08-mct-67 uettaxila says: on December 29, 2009 at 7:11 am

      it is good and working well

      • manjeet says: on May 10, 2010 at 12:30 pm

        please help about this project how to check the output of this ckt and which display used for this ckt.

    6. Matthew Baxter says: on January 11, 2010 at 4:40 pm

      I am going to use this circuit for a project i’m doing if you don’t mind. Can i please have the specifications for this circuit.

    7. Pancho Riado says: on March 31, 2010 at 6:08 am

      gracias amiga por el circuito …realmente funciona !

    8. phaneendra reddy says: on August 18, 2010 at 9:32 am

      thanq your circute is so help full to me

    9. hye! can u email me the full circuit and diagram. i really appericiate.

    10. hye! can u email me the full circuit and diagram.

    11. hye! i want to see your full circuit and component

    12. plz give me circuit diagram n explanation of digital thermometer

    13. bhavesh somani says: on October 4, 2010 at 9:33 am

      plz send me the circuit diagram n working of digital thermometer

    14. bhavesh somani says: on October 4, 2010 at 9:35 am

      plz send me circuit diagram n working of digital thermometer

    15. MITAL PATHAK says: on October 4, 2010 at 4:27 pm

      Plz send me the full circuit diagram with components list and workig of digital thermometer…

    16. Nikita Aloysius says: on October 6, 2010 at 7:26 am

      cn u plz send me the circuit diagram n working of digital thermometer?

    17. bhavesh somani says: on October 18, 2010 at 10:31 am

      plz send me circuit diagram of Digital Thermometer of file size at least 1 MB

    18. plz send me the ckt diagram and design in detail of digital room thermometer…

    19. Krishanu Sain says: on December 18, 2010 at 2:48 pm

      how i can make this digital thermometer? please send me the procedure for making this digital thermometer to my email address.

    20. we have to make this project complete finally displaying the output, in this circuit what have to be added to show the output ?? and do tell what are the precautions needed .

    21. madarchodf circuit hai

    22. plz give me more material in this topic…………..

    23. please send me its working principle in my email

    24. Plz mail me the details for the construction of a digital thermometer…please…its my project

    25. how to use this p1 and p2 resistor in our ckt.? its a varaible resistor… i am not understanding itz working in the circuit. n how the output of the temperature displayed,, i mean on what (& in volts or resistance)?? plzzz tell me ,,, its my project…

    26. Please send me full ckt diagram for this…. ths is my project n i need it badly, so plzzzz help yrrr.

    27. killemaru says: on July 22, 2011 at 4:38 am

      how to connect this to the display using PIC ? please send me a crkt connected this to the display with PIC .. thanks :)

    28. killemaru says: on July 22, 2011 at 2:49 pm

      we need documentation for the Digital electronic thermometer
      post it please

    29. leroy.... says: on August 7, 2011 at 8:23 pm

      cud u send me d entire ccircuit diagram wid d specifications..pls..its really urgent…need 2 do as project……..

    30. has anybody really tried this circuit out.. and does it work? please reply soon as i have to get started with it soon.. thanks.

    31. say the working principles of it.

    32. pls i wanna know about the capacitor which has been used. what is the range o.1 what.

      i made the circuit and used .1 micro F. but not working. pls send me details

    33. Hi

      This is what I need, thanks for it. But, It is only perhaps helpful in its present form for someone who would know how to make it (or figure it out) anyway.
      It needs a lot more detail as is suggested by most of the comments above.

      I would like to measure oil temperature and display it on a digital display or array of LEDs. Accuracy to only 1 or 2 degrees is adequate with a range from about 20 C to 90 C degrees.

      1) What would I use as a sensor?
      2) How would I hook it up to the display? I could probably figure this out with a little more research on my own, but if you have a schematic that would be great.

      Thanks for putting it out there


      • C.Mitra Chinmoy Mitra says: on July 24, 2012 at 10:00 pm

        Dear Gerry, you may use any small signal metal can transistor for the sensor, like BC108 or 2N2222, since the metal will conduct the heat much faster and better than the glass envelope of 1N4148 diode.
        As for the display, it can be any cheap digital multimeter set on the 200V range. The adjustment procedure given by the author is

    34. pls help me hw to use this as a project.

    35. i want full and more details about it pls send my email

    36. TRYMORE TAIMU says: on February 13, 2012 at 10:08 am

      want to use this project if anyone can help

    37. seems need more help on this one

    38. So, is the person/group that put this schematic on here watching this site?
      Is there more detail available?
      How do we know when it come on-line?


    39. sulaiman says: on March 11, 2012 at 8:53 pm

      pls, Waheed or anybody that have full circuit diagram of diode digitat thermometer should pls send it to me via my mail:abey124@gmail.com. this is my project thank you all

    40. sulaiman says: on March 11, 2012 at 9:18 pm

      pls, Waheed or anybody that have full circuit diagram of diode digital thermometer and project report should pls send it to me via my mail:abey124@gmail.com. this is my project thank you all

    41. nazirah says: on April 27, 2012 at 3:47 pm

      can plz send me a complete circuit of digital thermometer.. i really need it for my mini project..

    42. AYODEJI says: on June 2, 2012 at 1:24 am

      Please Waheed & any other person that can help me to pls send me the full diagram of the circuit and any other hint that can help me in achieving success in building the thermometer myself, I have interest in the project.

    43. can u plz send me a complete circuit of digital thermometer. i really need it for my mini project…..

    44. how does it work? when i heat the diode temperature is decrease….. whats the reason behind it plzz tell me

    45. i tried this circuit but I have a problem with the calibration. P1 does not seem to have an effect. why is that? I cant do the calibration. pls help

    46. josephparayaruthottam says: on January 31, 2015 at 5:03 am

      how to measure temperature.we get the output of multi meter as voltage.how to measure temperature

    47. Please send me more details of the experiment
      And also the components used in it
      What is a1,a2,a3
      Please reply me soon
      Thank you

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