The thermocouple signal is very small and must be amplified by considerable gain before it can be properly sampled by most ADCs. The AD8495 thermocouple amplifier provides a simple, low-cost solution for thermocouple temperature measurement. The integrated temperature sensor performs cold junction compensation. The fixed gain instrumentation amplifier amplifies the small voltage of the thermocouple to provide a 5 mV/°C output.
The amplifier has high common-mode rejection and is capable of rejecting common-mode noise that may be picked up by long leads of thermocouples. For extra protection, the amplifier's high-impedance input allows for easy additional filtering.
The AD849x output is a voltage proportional to the thermocouple measurement junction temperature (TMJ). To derive the measured temperature from the AD849x output voltage, use the transfer function TMJ=(VOUT−VREF)/(5mV/°C), VOUT=(TMJ×5mV/°C)+VREF. The AD8495 and AD8497 (Type K) instrumentation amplifiers have a gain of 122.4. With a single 5V supply, the 5mV/°C output allows these devices to cover a thermocouple temperature range of nearly 1000 degrees.
Comments 0
Leave a comment