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LM35 temperature sensing accuracy testing method used?

Anoop Joshi
Expert 1115 points
Other Parts Discussed in Thread: LM35, LMT70

Hi,

Can you please elaborate on the temperature sensing accuracy testing method used for verifying the temp sensing accuracy specification(<+/-0.75degC) for the LM35 part? Basically accuracy would be the difference between the actual/reference temperature and the temperature readout as per LM35 output right. How was the temperature forced over the device? Was a thermostream approach used (eg www.temptronic.com/.../ThermoStream_Overview.htm), or was a peltier based approach used(eg www.mechanical-devices.com/.../PageGen2.asp)? www.grantinstruments.com/.../1._high_temperature_oil_baths___circulators.pdf, us.flukecal.com/.../6330732073407380-comp-0)?

Thanks,

Anoop

  • 0
    TI__Expert 7220 points
    Hi Anoop,

    We use a stirred oil bath to test the accuracy of our sensors. This is used to ensure there is a uniform temperature medium around the temperature sensor IC. We also recommend a high accuracy RTD temperature probe to use as a reference.

    I noticed you have asked a lot of questions about the LM35. What is your application? We have newer temperature sensors with better performance than the LM35.

    -Michael Wong
  • 0 in reply to Michael Wong
    Expert 1115 points

    Hi Michael,


    Thanks for the confirmation. The application was actually to check the accuracy of one of our temperature sensors, so we wanted to verify the accuracy of our temperature forcing mechanism using a good reference temp sensor like LM35. I was interested in LM35 because of the easy temperature read out method using just an output voltage, rather than a digital readout, which results in a simpler board, I couldn't locate another temp sensor with voltage output with better accuracy.

    Can you also please let us know the name of the oil path unit used by you if possible

    Thanks,

    Anoop

  • 0 in reply to Anoop Joshi
    TI__Expert 7220 points

    Hi Anoop,

    You are correct, the LM35 output is easy to read, unfortunately its accuracy is only +/-0.5C at room temp. We have a new part out, the LMT70, which has +/-0.13C (max) accuracy at room temp and +/-0.36C (max) over the full temperature range of -55C to 150C. This part is also an analog output sensor, to convert to temperature use the look up table in the datasheet. We like the Fluke oil baths.

    -Michael Wong

  • 0 in reply to Michael Wong
    Expert 1115 points

    Hi Michael,

    Thanks for the suggestion, LMT70 appears awesome, unfortunately we have already released the LM35 board for fabrication, will plan to incorporate LMT70 in the next revision 

    Thanks,

    Anoop

  • 0 in reply to Anoop Joshi
    Expert 1115 points

    Hi Michael,

    Just want to thank you for suggesting LMT70 .

    We incorporated this part in our next revision board, and it is helping us tremendously in some critical projects.

    Thanks,

    Anoop

  • 0 in reply to Anoop Joshi
    TI__Expert 7220 points
    Hi Anoop,

    Thank you for using our sensor in your board. Let us know if you have any further questions.

    -Michael Wong