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LM335: Current Protection and EMI protection for circuits connected to LM335

Part Number: LM335
Other Parts Discussed in Thread: TMP235, TMP117, TMP107


I have a basic question for LM335 temperature sensor. Can i use it for railway tracks temperature measurement? Will there be any EMI interference or any high current induced into the sensor, that may in turn damage my controlled and ADC?

If yes, Please can you guide me to protection circuitry that can be used. 

  • Hello,

    Could you please provide more information about the surrounding environment? All sensors may be susceptible to EMI, and this is a very application-specific question. What kind of EMI levels are you expecting? What is the current and voltage level? How is the device being used to measure temperature?

    Typically, the sensors' signals can be protected from different types of EMI by using shielded and twisted-pair cables to mitigate capacitive and magnetic coupling.

  • Hello Audrey,
    We will be placing the temp sensor right below the railway track i.e. between the sleeper and track. For now we have no information about EMI levels that we may get. This is in a study phase. I wonder if there is a current induced due the railways passing on the track! Again no values available. Also we plan to supply lm335 with a 24 V Vref and R1 to be 24Kohms. (to maintain forward current 1 mA in uncalibrated mode) and connect it to a raspberry pi to send measured temperature every hour. Yes, if the sensor damages we have no problem, but we donot want it to pass any extra current to the Raspberry Pi controller as it is connected to many other sensors and hence the protection.

    Kind Regards,


  • Priyanka,

    Is there a particular reason why you chose LM335? What is the accuracy? Mounting style? Operating temperature?
    Have you consider our IC temperature sensors? Check out TMP235, TMP107, TMP117. Remember that with analog sensor you will have to consider error from the ADC as well. With digital sensors, the ADC is integrated and the total system temperature error is guaranteed in the datasheet. Digital interface will offer better noise immunity also.