• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 31 subscribers
  • Views 440 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

LM35: about high temperature

Hayashi
Expert 1840 points
Part Number: LM35
Other Parts Discussed in Thread: TMP117, TMP235

Hi team

My customer wants to know about the it linearity of sensing high temperature.
They have gotten the some data when they tested high temp of 98 deg.
Among  these data, some samples deviated from tolerance range.
Is not this suitable as a result?
Please let me know any imfomation about temperature linearity, if you have?
Best regards
Hayashi
  • 0
    TI__Expert 6475 points
    Hayashi,

    Which LM35 are you referring to? There are many variants.
    The definition of linearity is deviation of the output voltage from a best fit straight line. However, I wouldn't focus on this spec.
    I suggest focusing on the accuracy spec rather than linearity since you are ultimately measuring temperature (unless you're using the output
    voltage to compensate for a circuit).
    Please note that the datasheet spec doesn't include ADC errors.

    -Kelvin
  • 0 in reply to Kelvin Le THS
    Expert 1840 points
    Kelvin san

    Thank you for your reply.
    The device suffix is LM35DZ.

    I understand that focusing on the accuracy spec.
    In the case of this time, we found out that the LM35DZ deviated by more than 2℃ from the average value in the sample of less than 100 samples.
    Is this correct as a product?
    If it is a variation of something, please let me know if there is any foreseeable thing.

    Best regards
    Hayashi
  • 0 in reply to Hayashi
    TI__Expert 6475 points
    Hayashi san,

    2℃ error is within the possibility. The LM35D device itself is specified to a max error of 2℃.
    When you add ADC errors you will probably
    looking at 3-5℃ of total error. A major contribution of error is from the ADC reference.
    If you need more accuracy, check out TMP235 for analog or TMP117 for digital.
    The digital has ADC error included in the spec.

    -Kelvin
  • 0 in reply to Kelvin Le THS
    Expert 1840 points
    Kelvin san

    My customer has been gotten the data w/o ADC. They measured in the data of translated the output voltage.
    So, I think it is not the reason of error is from the ADC reference.

    Best regards
    Hayashi
  • 0 in reply to Hayashi
    TI__Expert 6475 points
    What measurement system are they using? How accurate is it?