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LM335: Temperature curve issue about LM335

Tom Tsao
Prodigy 250 points
Part Number: LM335

Hi E2E,

Good day.

Here is my application of LM335. And the block diagram is shown below.

 

 

I give 5V from PCB to LM335, and use MCU to sample the output voltage of LM335, then convert the voltage to corresponding temperature.

Then I put the whole set into a chamber to test it under different temperature condition.

In the beginning, the data show well and stable. However, when I change the environmental temperature in the chamber, the data fluctuate dramatically and could not recover.

So I want to inquire could TI provide me some internal test data of LM335 like the output voltage response in the period of temperature change.

I want to clarify the LM335 is able to work well in the range(−55°C to 150°C).

 

Thanks a lot!

 

  • 0
    TI__Intellectual 1660 points

    Hello Tom,

    1. Are you exposing the sensors alone to heat in the chamber or is the entire setup (as in the wires and connectors as well) being placed inside the chamber?

    2. What temperature range is the device being tested at in the chamber. For the LM335, its recommended operating range is -40*C-100*C.

    3. Have you tested the device outside the chamber in a different setup to check if the device is still failing?

    Regards,

    Harry Gill

  • 0 in reply to HarryG
    Prodigy 250 points

    Hi Harry,

    Here is my reply.

    1. Are you exposing the sensors alone to heat in the chamber or is the entire setup (as in the wires and connectors as well) being placed inside the chamber?

     I put all the setup (LM335 to MCU) in the chamber.

    1. What temperature range is the device being tested at in the chamber. For the LM335, its recommended operating range is -40*C-100*C.

      The temperature is 50~0C, within the operating range.

    1. Have you tested the device outside the chamber in a different setup to check if the device is still failing?

     Other setup works well, I've tried 5 sets of my product. Only one showed the wrong data.

    ========================================================================================================================

    I know there may be other issues that needed to be checked, like the connector, circuit on PCB. Due to there is only one set performing an abnormal situation.

    I want to inquire that if there some test data (temperature vs output voltage of LM335) you can provide me to prove that the LM335 is good enough to adopt on my product.

    Thanks for your help!

     

  • 0 in reply to Tom Tsao
    TI__Intellectual 1660 points

    Hello Tom,

    Unfortunately, we are unable to provide internal test data other than what is provided in the datasheet:

    This data is taken from a set of 30 devices.


    These device characteristics can be found on page 6 of the datasheet linked here.

    Hope this helps!

    Regards,


    Harry Gill

  • +1 in reply to HarryG
    Prodigy 250 points

    Hello Harry,

    Thanks for your reply, I still have some questions about this figure.

    1. The Y-axis of the figure is calibrated error. Does it mean LM335 is calibrated in 25C for no error, and over 185C may cause 2 degree error?
    2. This figure is derived by testing 30 devices. May I know the test content?

    LM335 is allocated in a chamber and keep reading its output voltage with different temperature?

    What is the temperature changing rate (like  +1 C/min.).

    And does the output voltage data be recorded within a stable temperature condition(like maintain the 25C for 5min and  then record the data)?

  • 0 in reply to Tom Tsao
    TI__Intellectual 1660 points

    Hello Tom,

    1. Yes the LM335 is calibrated in ambient conditions (25*C).

    2. Unfortunately, we are unable to provide testing details as that is proprietary information.

    - The device is typically tested in a temperature controlled environment to ensure accurate readings over temperature.

    - The device is also typically allowed to "soak" for enough time at a temperature to make sure it's thermally stable before taking the measurement.

    Hope this answers your questions!

    Regards,

    Harry Gill