AD8495

Hi all,

I have a board desegned to measure temperature with a K-Type thermocouple.

In orther to measure temperature with a T Type thermocouple can i use the the AD8495 IC?

In the AD595 datasheet that seems a previous version of the chip, we can use the T type thermocouple for an ambient temperature range 0-50°C.

Best,

Stefano 

  • Hi Stefano,

    Thanks for using ADI product in your design.

    I think you can use AD8495 for T-type thermocouple but it depends on the temperature range. Take a look at the graph below. K-type Seebeck coefficient's is roughly constant at 41uV/°C from 0°C to 1000°C while the Seebeck coefficient of T-type thermocouple approximately increases in linear rate. For T-type thermocouples, at 0°C the output changes at 39uV/°C but at 100°C the output changes at 47uV/°C. Since the graph of the T-type is linear, by computation at 25°C the coefficient is 41uV/°C as supported by the table below, and at 50°C it would be 43uV/°C. So it means that the output will differ from the nominal 5mV/°C because of the response of the T-type thermocouple when operating at higher temperatures.

          

    For AD595, the specified temperature range from the datasheet is from 0°C to 50°C

    Thanks,

    Jay

    .

  • 0
    •  Analog Employees 
    on Jul 7, 2014 9:36 PM over 6 years ago

    Hi Stefano,

    Jay has this right. Because we know that T-type thermocouples are similar to K-type thermocouples near room temperature, we can use K-type thermocouple amplifiers such as AD595 and AD8495 in order to amplify T-type thermocouples and perform the cold-junction compensation. But as Jay said, because the slope of the T-type thermocouple is much less constant over the entire range, we cannot simply model the output slope as 5mV/°C. Here is a graph generated from the T-type NIST table showing the approximate AD8495 output vs temperature with a T-type thermocouple. Feel free to use the graph or the polynomial fit for your system.

    Best regards,

    Scott

  • 0
    •  Analog Employees 
    on Aug 2, 2018 2:40 PM over 2 years ago
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin