Hello everyone, I am new on this forum and I hope that you will be able to help me. I am trying to build a carbon monoxide (CO) detector for classic cars using a hot wire as sensor. The idea is to expose a "heating element" to exhaust gas. The resistance change of the hot wire would be proportional to CO percentage in the exhaust gas. The idea is to be able to detect between 0% and 10% ( from 0 ppm to 100000 ppm) ±0.1 CO. First of all please see Fig.1 which shows the wiring connections. the wire is heated by DC voltage (1.5V - 3.5A). Please see Fig.2 for the schematics of voltage supply and sensing chamber (sensor). I have added buck converter after AC to DC converter to be able to have a better control on voltage/current. The output voltage of the sensor would be directed to ADC. To prevent its destruction, I thought to attenuate the signal with PI pod attenuator, Fig 3 . To be able to achieve required attenuation I needed circa 0.7 Ohm resistors, to do so I connected several 1 Ohm and 10 Ohm resistors. Firstly I was using MCP3421 (datasheet attached) as ADC but I think it would be too sensitive for the "highly" technological for the hot wire sensor. So I have switched to the inbuilt Arduino uno ADC using 5V reference. But I still cannot get a steady reading unless I start to average the readings, which would increase time response. Could you please help me with some inexpensive signal conditioning? Or advice me how to improve the reading?