Hi Frank, it doesn't really matter if the NTC is on the high or low side. It also doesn't matter if you measure the voltage with the ADC across the NTC or RREF. It's all just a resistor divider. Please remember that you would have to bypass the PGA of ADS1220 or ADS122U04 in your configuration. If you wanted to use the PGA to increase the input impedance slightly, you would have to use an excitation voltage which is less than the analog supply of the ADC and then measure differentially across the upper resistor as I have shown in one of my previous figures. But I would try your setup first. Regarding the RC filter. Please follow my guidelines in the ADS1219 datasheet, section 9.1.4. If you don't need the series resistors to protect the ADC inputs from overvoltages, then I would make them relatively small. Regards,
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