• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 46 subscribers
  • Views 1233 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

How to calculate J-Type Thermocouple Temperature using ADS1118?

ADS1248: How to calculate J-Type Thermocouple Temperature using ADS1118?

siddharth rana
Prodigy 75 points
Part Number: ADS1248

i am using ADS1248 for thermocouple application.using other temperature sensor for cold junction measurement .

using a universal calibrator i m injecting milivolt in to adc channels.plus all the channels are baised using 1 M resistor value between avdd and agnd.

but my converted value reading is 0x001h ,0x002h.

and converting it to milivolt it gives 0.70mv at every other injected milivolt .

  • 0
    TI__Guru* 92655 points
    Siddharth,


    I need a better description of your problem. Are you saying that the calibrator puts out exactly 1.0mV, but you read 0.70mV? I think it would be best to post a block diagram or schematic for your setup, showing all of the connections and any input filtering that you might have.

    Second, I'd like you to show the output data from the ADC. If you're using the ADS1248, then show all 24 bits of output data so it is possible to do an exact conversion. You gave two values for your reading of 0x001h and 0x002h. It would be better to give the exact data and say how the measurement reading changes

    Regardless, thermocouple readings are generally very small to begin with. If the input is 1mV, then it doesn't take much to add some error to the measurement.


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Guru* 92655 points
    Siddharth,


    I haven't heard back on this question for a while. Were you able to solve your problem? As I'd mentioned, I'd need much more information about the data you're getting and the setup of the ADS1248 to help solve your problem.

    I'll close this post for now, but if you continue to have problems reading data, post back and we can continue to work on this. Again, I'll need much more information on this.


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Guru* 92655 points
    Siddharth


    As an additional comment, there is a new application note on the measurement of thermocouples with precision ADCs. The note is titled "A Basic Guide to Thermocouple Measurements" and can be found in the link below:

    www.ti.com/.../sbaa274.pdf


    Joseph Wu