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LTC2986 measure differential thermocouple with universal input circuitry

Hi,
I'm planning to use a LTC2986 to measure a bunch of different sensor types with only one hardware setup. In the datasheet I found a schematic of a typical application (last page) which seems to work just fine for my application. I was just wondering if it would be possible within this setup to connect a thermocouple to the terminals in differential mode and not only single-ended.

Thank you in advance!

Kind regards,
Ben

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  • Hi Ben, 

        That will be OK - the thermocouple can be differential on CH2-3, 4-5, etc. Keep in mind that you'll need the diode on CH6 or another (non-TC) sensor further down as the cold-junction compensation sensor. 

        Also keep in mind that the inputs are high-Z - the differential thermocouple signal could float outside the common mode range of the part unless it's tied to something - a bias voltage or GND through a resistance. The inputs can go 50mV below ground so a TC with negative tied to GND can still go cold and be measured accurately.

    Hope it helps,

    -Logan

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  • Hi Ben, 

        That will be OK - the thermocouple can be differential on CH2-3, 4-5, etc. Keep in mind that you'll need the diode on CH6 or another (non-TC) sensor further down as the cold-junction compensation sensor. 

        Also keep in mind that the inputs are high-Z - the differential thermocouple signal could float outside the common mode range of the part unless it's tied to something - a bias voltage or GND through a resistance. The inputs can go 50mV below ground so a TC with negative tied to GND can still go cold and be measured accurately.

    Hope it helps,

    -Logan

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