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LMT70: Using LMT70 for measuring body temperature

Abhishek singh
Expert 2000 points
Part Number: LMT70
Other Parts Discussed in Thread: CC2640R2F, ADS1115

Hi  Team 

We have to make  one wearable having  various  bio sensor and we have  to  measure human temperature. For sensing  human temperature we are planning to use  LMT70, i observed in the  various  refernce  desgin TI used one additional ADC along with uC.

Please  let me know following

1) Can i use  CC2640R2F  ADC  and still  get fairly good  result of temperature ?

2) Can you  please  let  me know  the part  no/(or suggest some other) epoxy  used in TIDA 00824.

  • 0
    TI__Guru* 90906 points

    Dear Abhishek -
    The ADS1115 is 16 bit sigma-delta ADC, with 16 bits effective (slower (~860 samples per sec). The CC2640R2F has SAR 12 bit ADC which is 10 bits effective (faster (can do 200ksps)).
    The LMT70 is going to put out ~5mV per degree, so 10 bits effective may be "good enough", it really depends on your specific application requirements.

    There are 2 code projects on dev.ti.com for the CC2640R2F ADC if you want to check them out -
    This one takes 200sps dev.ti.com/.../node
    This one is a single sample example: dev.ti.com/.../node

    The thermal grease or paste is not special - you should be able to get from any electronics distributor (brand names I know are Wakefield-Vette, Chemtronics, MG Chemicals, t-Global Technology, and others)


    BR -
    Josh

  • 0 in reply to Josh Wyatt
    Expert 2000 points
    Hi Josh
    Thanks for providing me details . In my device i have to measure skin temp as well as Ambient temp . Can i use same LMT70 for both by saying that if you want to measure you temp put hand one top metal strip and once you remove hand it will measure Ambient temp.

    1)Do you suggest to do this ?
    2) if this approcha will be reliable for measuring Ambient temp or i should make hole in the device and let copper pad interact with air.?
  • 0 in reply to Abhishek singh
    TI__Guru* 90906 points
    Abhishek -
    The TI Design referenced uses two LMT70 parts, one for ambient and one for skin. I think this is the recommendation - if you want to modify the reference and test it for your own needs, this of course is possible for you to do.