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INA350: INA350

Keyur Parikh
Prodigy 50 points
Part Number: INA350
Other Parts Discussed in Thread: INA351, TLV9041

Tool/software:

Hello TI Team,

We intend to use INA350 to interface the thermocouple.  So could you please suggest the design ? 

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Regards

Keyur Parikh

  • 0
    Prodigy 50 points

    Hello TI Team,

    Waiting for your further inpur.

  • 0 in reply to Keyur Parikh
    TI__Genius 15726 points

    Hi Keyur, 

    Sorry for the delay, it is currently US Holiday. 

    Here are some design questions I have:

    What type of thermocouple do you intend to use?

    What is the desired temp range to measure?

    What is the output range you intend to use?; Example : (.2V to 3.1V)

    What accuracy do you require?

    What supply voltage will you be using?

    We have a great application note which covers interfacing with thermocouples here: 

    You will see there are many different ways of implementing this circuit.
    Knowing some of the above mentioned details will allow me to create a simulation.
    Thanks,
    Jacob
  • 0 in reply to Jacob Nogaj
    Prodigy 50 points

    Hello Jacob,

    Thanks for supporting. Please find below replies for questions.

    What type of thermocouple do you intend to use? 

    K : Currently using K type. But We are planning to all type thermocouple.

    What is the desired temp range to measure?

    K : 0'C to 1450'C

    What is the output range you intend to use?; Example : (.2V to 3.1V)

    K : Yes like this. 

    What accuracy do you require?

    K: +/- 5'C

    What supply voltage will you be using?

    K : We are working with 3.3V micro controller.

    Regards

    Keyur Parikh

  • 0 in reply to Keyur Parikh
    TI__Genius 15726 points

    Hi Keyur, 

    Here is a simple design which should work for your needs:

    INA351_Thermocouple_K.TSC

    Note, I am using the INA351CD here as the INA351 is like the INA350, just with an internal buffer on Vref. This means you can directly connect any source impedance with Vref without concern of error in the difference amp stage of the INA. 

    I simulated the type K thermocouple from -5mV (~-200C)  to +55mV (~1370C).

    You are welcome to change the Vref and the thermocouple input voltage as needed. 

    It may also help to install a differential filter on the input to the INA, but this is optional depending on the high frequency rejection characteristics you require. 

    Please let me know if you have any questions.

    Best,

    Jacob

  • 0 in reply to Jacob Nogaj
    Prodigy 50 points

    Hello Jacon,

    Thanks for reply. Let me go through design and i will contact if needed. 

  • 0 in reply to Keyur Parikh
    Prodigy 50 points

    Hello Jacob, 

    Any other Op-Amp for same application. I do not want to put more hardware. 

    Could i use shunt sensing Op-Amp for this application ?

    Regards

    Keyur Parikh

  • 0 in reply to Keyur Parikh
    TI__Genius 15726 points

    Hi Keyur,

    This is already a pretty simple design. I selected INA351 instead of INA350 to effectively reduce hardware and board size for thermocouple design. 

    What is the problem with the above design? Do you not want TLV9041 included? It may be possible to get away with a resistor biasing of the thermocouple, but this could influence accuracy. 

    Shunt monitor will still require some biasing of the thermocouple to ensure linear operation of the amplifier.  

    Thanks,

    Jacob