AD849x amplifiers for J and K type thermocouples

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The AD8494 , AD8495 ,AD8496, AD8497 are easy to use amplifiers for J and K type thermocouples , that convert a small voltage generated by a thermocouple junction into a signal that can easily be read by an analog-to-digital converter (ADC) or microcontroller. The gain from the thermocouple to the amplifier output is approximately 5 mV/°C.

The AD849x contains a high precision instrumentation amplifier. This amplifier 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 AD849x allows a wide variety of supply voltages 2.7 volts up to 36 volts  for single supply and from ±2.7 volts  up to ±18 volts for dual supply .

Also the AD849x can easily measure negative temperatures ,the 0°C output can be adjusted with a voltage on the reference pin.

Also the AD849x can be used for ambient temperature sensor , by disabling the thermocouple  sensing functionality , by shorting it inputs to ground  ; and the AD849x simply outputs the value from the on board temperature sensor .

Main features of the AD849x main features are : integrated cold junction compensation , 5-mV/°C output with single-supply operation down to 2.7 V and rail-to-rail output , high-impedance differential input, reference pin allows offset adjustment, wide power-supply range: 2.7 V to ±18 V, high gain accuracy – 0.1%,low power: 180 µA quiescent supply .

AD849x temperature sensor circuit diagramAD849x ambient temperature sensor circuit diagram

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