• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 30 subscribers
  • Views 113 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

LMT01: Temperature sensing accuracy becoming less accurate with a rapid temperature rise

Kent Hayes
Prodigy 10 points
Part Number: LMT01

Tool/software:

Hello,

I am using the LMT01DQXR component in my design to measure temperature of another electronic component within the assembly. I am performing a high temperature operation test, where I soak the unit at +40C ambient temperature for one hour and then power on my device for operation. I've placed some thermocouples within the assembly to monitor temperature of the same components of interest. This will ensure thermocouples and LMT01DQXR will be at least within 3C from one another.

As I am reviewing the temperature data being reported by the LMT01DQXR, I see it does accurately measure temperature data as it has been soaking at the +40C ambient temperature. However, as the device is placed into operating mode, temperature rises, and the temp sensor eventually reports a value that is more than 15C from what the thermocouple is measuring. Is there any explanation for why the LMT01DQXR would measure less accurately as there is a temperature rise?

 

  • 0
    TI__Mastermind 43835 points

    Hi Kent,

    Can you tell me about how you've implemented the signal acquisition? Please share a schematic and some code/psuedo-code for the capture of the pulse count.

    • I recommend powering down the LMT01 between measurements to make sure you are synchronized with its outputs. The longer LMT01 is on, the more its timing could move away from you capture device's expected timing for conversion and data periods.
    • If you count pulses for too long (about 100ms,) you would capture counts from two different results. 
    • LMT01's internal oscillator is expected to vary over temperature, which is covered by TDATA and TCONV min/max specifications. The oscillator of your capture device would also vary with temperature, and could result in capture windows drifting towards each other or away from each other as temperature changes.
    • EMI sources in your application could be changing with temperature, and these could induce extra pulses into the LMT01's signal. This would increase the perceived output.

    thanks,

    ren