Analog Devices AD8494/AD8495/AD8496/AD8497 thermocouple amps

The Analog Devices AD8494/AD8495/AD8496/AD8497 are amplifiers for J- and K-type thermocouples.

They convert the small voltage generated by a thermocouple junction into a signal that can be read by an analog-to-digital converter or microcontroller.

The gain from the thermocouple to the amplifier output is about 5 mV/°C and the AD849x performs cold junction compensation using an onboard temperature sensor. Thermocouple measurements stay accurate through a wide range of ambient temperatures.

It contains a high-precision instrumentation amplifier that has high common-mode rejection, which allows it to reject common-mode noise that the long lead thermocouples may pick up.

For additional protection, the high impedance inputs of the amplifier make it easy to add extra filtering.

The amplifier allows a wide variety of supply voltages. With a 5 V single supply, it can cover nearly 1000 degrees of a thermocouple’s temperature range and works at 3 V, allowing it to directly interface to lower supply ADCs.

It can also work on supplies to ±18 V in industrial systems that require a wide common mode input range. Whatever the supply rails, the amplifier can easily measure negative temperatures.

The 0°C output can be adjusted with a voltage on the reference pin. This gives flexibility in adjusting the output range to fit the ADC. The robust inputs are designed to handle real-world connection scenarios.