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ADS114S08: PT100 measure signal with 0.5°C max error

Marvn Arcangel
Genius 10485 points
Part Number: ADS114S08
Other Parts Discussed in Thread: ADS1261, ADS1278-HT, ADS1243-HT

Hi Team,

Our customer is looking for a way how to measure PT100 signal with 0.5°C max error. Additionally, the customer also needs to measure 4x pt100 simultaneously within a quality of 1°C.

If this is not possible using this IC, can you suggest an alternative? can you also suggest a humidity sensor IC preferably with humidity protection to 150°C to be used with ADS114S08 (or the alternative)?

Thank you.

Regards,

Marvin

  • 0
    TI__Guru** 113765 points

    Hi Marvin,

    First I would recommend that the customer review the information in A Basic Guide to RTD Measurements.  This document shows example circuits and excitation methods for RTD measurements. 

    The ADS114S08 is a muxed input device and not a simultaneous sampling device (SIMSAM).  The issue with our SIMSAM devices is that they do not incorporate current source excitation for measuring multiple input channels.  Double check if there is a specific need to measure all four RTDS at exactly the same time or if a muxed input device would be acceptable.  For example, the ADS1261 could cycle through the mux much faster than the ADS114S08.

    I think the bigger request is operation at 150 deg C at high humidity.  Most of our devices operate in the industrial temperature range up to 125 deg C, and would require some form of encapsulation or potting material over the IC.  Also, there are not very many devices for precision ADCs that can operate at high temperatures.  There are two that I can think of and they are the ADS1243-HT (muxed input and no IDACs) and the ADS1278-HT (SIMSAM) and they sell for > $100 US each.  Also these devices would required additional circuitry for the analog front end.

    Best regards,

    Bob B