ads248 pt1000 reading incorrect values

Discussion in 'Embedded Systems and Microcontrollers' started by aamirali, Feb 15, 2014.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
    I have a strange problem in reading pt000 connected to ads1248.
    when i measure resistance of pt000 by external meter values comes out to be 1070 ohms correctly.
    but when i try to measure it by ads1248, it is less than half.
    so i checked it by fixed resistance of 1070 ohms created by pot i gt correct values.
    no change in code & hardware. i am using 100ua current

    i also used other pt1000, all are giving same problem.
    if pt1000 have problem it shouldn't correct value on external meter also.
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
    I think: when you have pt1000 connected to ads1248, you are not measuring one resistance, you are measuring two resistances in parallel. When you have two resistances in parallel, the equivalent resistance is smaller than either of the originals.
  3. aamirali

    Thread Starter Member

    Feb 2, 2012
    no i am measuring only one
  4. paulfjujo

    New Member

    Mar 6, 2014

    What range of measurement you have on your ads1248
    are you using single end or differential
    with 16bits single end , you can measure (unsigned int16) 0 to 65535
    with 16 bits differential =>( Signed int16) -32768 to + 32767
    Half positive range !