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ADS1248: To measure temperature upto 0.01 Degree accuracy

Abhijit Gajare
Prodigy 30 points
Part Number: ADS1248
Other Parts Discussed in Thread: ADS1247, ADS124S08, , ADS124S06

Hi,

I want to measure temperature of a small furnace with accuracy of 0.01 Degree.

I want to read two channels. I am planning to use PT1000 sensors for better resolution. 

The temperature range I want to monitor is 0 Degrees to +400 Degrees.

My sampling rate can be as low as 10 samples per second per channel ( i.e. 20 samples per second ).

I can use external reference, and dual power supply if required by the design. 

Can you suggest me, whether this IC is suitable for my application ?

Abhijit Gajare

  • 0
    TI__Guru* 97415 points
    Abhijit,


    I would highly recommend reading this example design:

    www.ti.com/.../slau520a.pdf

    This outlines the design of a 3-wire RTD measurement system. It shows many of the calculations and measurements required to show what sort of accuracy you would get out of this type of measurement system. This design is for the ADS1247/ADS1248, which would get you close to that sort of accuracy. The new ADS124S06/ADS124S08 is a similar device, with slightly better specifications.

    I would note that the measurements in the example design show very good measurement accuracy. However, there are several things that are very important to consider. First, the measurement is done with precision resistors so that the ADC gain error can be precisely calibrated. This design presumes that the operating temperature of the device is kept at the same temperature so that there is no ADC offset or gain drift. Also, in the example design, the precision resistors are measured with an Agilent 3458A, and then the ADC measurement is calibrated to the data. The reference resistor is also required so that the gain error and gain error drift are kept low. Also, even if you are able to measure the resistance of the RTD precisely, there is some error associated with the RTD itself. Even the most precise RTDs, have an intrinsic error. If you use the 1/10 DIN type RTD, the error (1⁄10 DIN = ±1⁄10 * (0.3 + 0.005*t)°C).

    My guess is that the both the ADS1247/ADS1248 and the ADS124S06/ADS124S08 are capable of an accuracy and precision that is similar to what you are after. However this requires significant calibration that may make that type of temperature measurement accuracy difficult. Even with the best RTDs, you may be unable to get your desired accuracy of 0.01°C.


    Joseph Wu