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ADS1220 internal data averaging

Samuel Tal
Prodigy 130 points

Other Parts Discussed in Thread: ADS1220

I use the ADS1220 to read type B thermocouple. 

The Type B output is extremely low at low temperature (30 microvolts @ 100 deg C), which
necessitates averaging for filtering.

While the 1220 can sample at 1000 SPS at the background, for practical temp reading 20 SPS is more than sufficient.

The question is if anyone knows if there is a way to make the 1220 read and internally average at 1000 SPS, while the program reads at
lower rate (20 SPS or even single shot per call), or is there another device that can do it?

It seems a real waste if this is not possible, as the 1220 could provide the averaging at the background at no cost. 

Samtal

  • 0
    TI__Guru** 113765 points

    Hi Samtal,

    The ADS1220 is a delta-sigma data converter where many samples are taken and processed through a digital filter.  The samples are taken at the modulator rate of 256kHz while operating in normal mode and internal, or external, clock frequency of 4.096MHz.(see section 7.1 on page 15 of the datasheet.)  In the case of 20sps, a special FIR filter can be used to achieve 50/60 Hz rejection.  You can see the different filter characteristics at the various data rates in section 8.3.4 of the datasheet starting on page 24.  In the end the filter response is a little more complicated than a simple averaging filter.  Of course you can always include additional averaging of the conversion data if desired.

    Best regards,

    Bob B