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LMT87: RC Filter on remote ADC end & the Series Resistor on the Sensor end

Neet
Intellectual 622 points

Part Number: LMT87

Tool/software:

Hello E2E Team,

We are planning to use LMT87 for our remote temperature measurement use case with sensor being encapsulated inside a SS Metal Probe.

I want to understand for a CAT6 Twisted pair cable length of 6m from sensor to the ADC - followed by a RC based LPF filter on the ADC side with R=1kOhm or 100kOhm & C= 0.1uF or 1nF do we need to install a series resistor on the sensor side?

Assuming the Resistor of the RC Filter will act as the isolating/stability resistor & the effective C_Load that the LMT87 experiences is effectively only the cable capacitance of about 300pF which is far less than 1100pF limit as mentioned in the datasheet.

Kindly guide.

  • 0
    Intellectual 622 points

    Also suggest a better RC Filter configuration for an effective cutoff of about 1kHz to 2kHz range.

    1. R: 1kOhm & C: 100nF
    2. R: 10kOhm & C: 10nF
    3. R: 100kOhm & C: 1nF

    Let me know which RC Filter configuration is better suited for the LMT8x series analog sensors.

  • 0 in reply to Neet
    TI__Genius 14505 points

    Neet,

    If the cable capacitance is really only about 300pF, then you will not need the series resistor at the sensor side for stability, you are correct about that. I believe all of these options should be fine, you can go with option 1 if you really aren't sure.

    Thanks

    -Alex Thompson