I don’t really know what “bottle” you have, or whether the gas inside it is a liquid. But I am interested in your project. My situation would be an outdoor barbeque, with a rather fat, almost spherical, propane tank. One can’t ever put anything inside that tank, so the “noninvasive” idea is very absolute. Recommended proceedure is to pour hot water down one side of tank, and measure resulting temperatures over time after the pour. The liquid does strong cooling, especially at its top surface. You want to never get the tank wall hot enough to ignite a propane-air mixture inside or thermally-stress the tank. So, always less than 100c. Using lots of electric power is inconvenient and dangerous, so invent reductions of resistor-heating time, test rate, and area. Make your “thermal-capacity/thermal-resistance” test sensitive to the minimum temp.-rise that clearly tells presence/absence of liquid content, covering only one spot on the shell, low on the tank, with thermal insulation over and around the heater-spot. With luck the sensor could be one 5-cm foam-rubber patch glued to the shell. A small separate electronic board with indicator LED, “test now” button, and power supply (battery?). You decide where you want that board to live. 2-4
thin wires between sensor & board. That is what I would like to imagine.

Please read the whole thread above. Potentiometer influences only threshold of D0 pin. The A0 pin is analog out. A0 ignores the potentiometer setting; it gives a variable voltage output from the sensor. Yes you can read both simultaneously. It is probably smarter to do so. The digital pin is, in many senses, less powerful than the analog pin. D0 cannot give you the full-range data A0 gives you. So use A0 for sure. D0 is only a shortcut for simpler systems that don’t interpret A0.

We assume you fixed your error

I wondered about the power consumption from the arduino myself. These are quite power hungry. My device said to burn in as well.
These are not for battery operated systems.

connect sensor data pin to analog pin of the controller, then corresponding to input gases analog readings will change