I am using AD8220 for temperature measurement (using thermocouple). The circuit below is only hot junction measurement, for cold junction reference measurement I use a separate RTD
I was testing the part @ 125 C and observed that it had stopped functioning. The amplifier was drawing about ~10mA current from my voltage reference(normal current consumption should be ~750 uA). I use ADR4550 for 5V reference. Could it be because I am not providing the return path for the bias current of the amplifier?
Below are some of the design details
My input voltage from J type thermocouple is 0-18.8 mV (0-345 deg C)
Gain: 99.8 (Rg=500 Ohms)
Differential and common mode filter before AD8220 (fdiff cut off = 7.57 Hz, fcm cut off = 159.155 Hz)
Vref = 1 V
Would the below circuit solve the issue ?
Appreciate your input on this
Thanks & Regards,
Read chapter 5 of the inamp handbook 3rd edition.
You have to return bias current to ground.