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TMP114: Get real time measurement no average

johan lantz
Prodigy 30 points
Part Number: TMP114

Tool/software:

I have played with the sensor but it seams to do average measurement but I need the current value and not the average. Is this possible to do?

For the config I use the following:

TMP114_CONFIGURATION_REG <- TMP114_ADC_TIME_1mS_MODE_CMD | TMP114_CONTINUOUS_MODE_CMD | TMP114_CONVERSION_TIME_7mS_MODE_CMD

  • 0
    TI__Expert 7170 points

    Hi Johan,

    The TMP114 has an average enable bit which is set to 0 by default (not averaging). On reset, you would be reading a single conversion from the temperature sensor. The conversion mode does not affect whether the device averages or not--these are 2 separate settings.

    Best regards,

    Simon Rojas

  • 0 in reply to Simon Rojas Avila
    Prodigy 30 points

    Yes the average bit is not set so it should be zero. I still see that the readings is not changing as it should if it was not running some kind of averaging in the background. If I put a finger on the sensor I can see that it jumps from 23 to 32, then it slowly going up with 0.3 every 1 or 2 seconds interval. 

  • 0 in reply to johan lantz
    TI__Expert 7170 points

    Johan, 

    This behavior seems fine to me if you are running in continuous conversion mode at the default conversion period rate. The device will convert at 4 Hz by default so seeing a jump in temperature soon after placing your finger on the device and seeing it slowly decrease in time after taking your finger off makes sense. Consider that the device will absorb heat very quicky due to the chip-scale package but when it comes to dissipating that heat, this will depend on the thermal conductivity of the PCB, solder balls, etc. If you want to see a more continuous rise in temperature as you place your finger on the device, consider increasing the conversion period rate of the device as well as the sampling rate of your SW / µC.

    Hope this helps.

    Best regards,

    Simon Rojas

  • 0 in reply to Simon Rojas Avila
    Prodigy 30 points

    I now as you can see above have the fasted conversion time of 7ms, but you want me to set higher (like 2 second) to get faster temperature changes? I do not fully understand what you mean by "your SW sampling rate"? Will the read from the device behave differently if read from it more often or less? 

  • 0 in reply to johan lantz
    TI__Expert 7170 points

    Johan,

    The device output will always be the same regardless of SW sampling rate. If you are constantly reading the the temperature register of the device when you are running your bench test but are not seeing a proper increase in temperature, then you are likely not reading the temperature register fast enough to see all of the conversions from the device--hence why I suggest increasing the sampling rate. The device will not average multiple readings by default which can be proven by monitoring the quiescent current of the device and calculating the active conversion time to compare it to the datasheet spec:

    If further support is needed, I would ask you to please provide a plot or data of the behavior that you are seeing. Thank you.

    Best regards,

    Simon Rojas

  • 0 in reply to Simon Rojas Avila
    Prodigy 30 points

    I will let you know in more detail the values we read when running this as attended. Now I only test it before we use the application.in a real scenario involving measuring a surface temperature that will be PID controlled with the TMP114 sensor as input for the calculation. First try failed with to slow changing of the temperature value leading to the PID calculation not providing the correct regulation. Now I have changed it as described in my first post and if we still see an issue I will let you know, I will close it now and reopen if we still have an issue,