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    PT100 with PIC microcontroller

    Dear ALL,

    i need a cisuit PT100 temparture sensor using pic ADC. your help will be highly appricated

    Regards

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    Re: PT100 with PIC microcontroller



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    •   Alt29th May 2010, 16:18

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    PT100 with PIC microcontroller

    thx IanP

    any one here to share practically used circuit ?



    •   Alt31st May 2010, 09:58

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    Re: PT100 with PIC microcontroller

    Here is a nice example of a compensated, opamp-based circuit that interfaces the PT100 to a microcontroller ..
    http://pdfserv.maxim-ic.com/en/an/AN3450.pdf
    It's based on MAXIM opamp, but I can't find any reason why it wouldn't work with any other rail-to-rail device ..

    Here is another one: "A precision interface for a Resistance Temperature Detector (RTD)"
    http://www.national.com/nationaledge/dec04/article.html
    Again, you are not obligated to use the specifically indicated opamp .. any rail-to-rail will do ..

    IanP
    :D


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    •   Alt31st May 2010, 12:00

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    Re: PT100 with PIC microcontroller

    Can I use 741 Op amp with the circuit shown here http://www.edaboard.com/attachments/...face1_5420.gif

    What changes should I make to the circuit?????



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    Re: PT100 with PIC microcontroller

    Quote Originally Posted by internetuser2k11 View Post
    Can I use 741 Op amp with the circuit shown here http://www.edaboard.com/attachments/...face1_5420.gif

    What changes should I make to the circuit?????
    This circuit [pt100-precision-interface...] is designed to work as an instrumentation amplifier, and some of opamps’ inputs work with voltages very close to 0V/GND. For that one needs a rail-to-rail opamp.
    The LM741 has a minimum supply voltage, which from the top of my head is somewhere around +/-6V, that makes 12V single voltage configuration.
    If you want to connect output of [pt100-precision-interface...] to a microcontroller it has to be supplied of a single 0-5V power source. In this instance the LM741 is completely useless.
    Google for a rail-to-rail in/out opamp that is meant to work with single supply rail ...

    IanP


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    Re: PT100 with PIC microcontroller

    OK. I used the same OP AMP as mentioned in the circuit. It is working fine. I want to know the exact o/p it gives / degree centigrade rise in temperature. including the increase in RTD resistance with increase in Temperature.

    How much does the resistance of rtd pt100 increase / degree C.

    what is the formula to be used with the above circuit for calibration???????????

    ---------- Post added at 11:39 ---------- Previous post was at 11:17 ----------

    Also I want to know the value of C1 @ this link http://www.edaboard.com/attachments/...face1_5420.gif

    Is it 1F or 1uF?

    ---------- Post added at 13:11 ---------- Previous post was at 11:39 ----------

    Quote Originally Posted by IanP View Post
    Here is a nice example of a compensated, opamp-based circuit that interfaces the PT100 to a microcontroller ..
    http://pdfserv.maxim-ic.com/en/an/AN3450.pdf
    It's based on MAXIM opamp, but I can't find any reason why it wouldn't work with any other rail-to-rail device ..

    Here is another one: "A precision interface for a Resistance Temperature Detector (RTD)"
    http://www.national.com/nationaledge/dec04/article.html
    Again, you are not obligated to use the specifically indicated opamp .. any rail-to-rail will do ..

    IanP
    :D

    What is the o/p mV/Degree C of the above circuit?

    The o/p of the circuit http://www.edaboard.com/attachments/...face1_5420.gif is not linear. What is its o/p formula?

    ---------- Post added at 14:28 ---------- Previous post was at 13:11 ----------

    What is the equation for the circuit http://www.edaboard.com/attachments/...face1_5420.gif

    The o/p is not linear.



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    Re: PT100 with PIC microcontroller

    The circuit shown here http://www.edaboard.com/attachments/...face1_5420.gif is giving an o/p of 0.01V @ 850 Degree C.

    I am getting wrong value. Please help me with the circuit. Tell me how to get the rtd pt100 resistance and temperature from Vo.



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    Re: PT100 with PIC microcontroller

    @internetuser2k11 - How did you get the actual temperature value from Vo? Did you build a look up table? Where to find a look table for PT100 RTD - from the manufacturer?


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    Re: PT100 with PIC microcontroller

    vishay have nice application notes and informations:
    http://www.vishay.com/resistors-non-linear/
    http://www.vishay.com/resistors-non-...putation-list/
    you get excel table .... insert your sensor data and you get values....

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