You can use a chemical CO2 scrubber (e.g., bubbling air through a saturated solution of calcium hydroxide) to get a rather stable/repeatable sub-ambient reference to calibrate the sensor with.
An aquarium bubbler , or rather two, should be easy to plumb to a CO2 sensor. Just skip the water bath for one of them.
The calcium hydroxide is sold as "hydrated lime" and needs to just be stored isolated from CO2, and is mildly basic, so will slowly corrode your fingers (wash after touching, don't get any in your eyes).
Shouldn't even need gloves for this usecase, where one occasionally swaps the water and sediment for fresh stuff.
Btw, the waste, after soaking CO2, is just harmless limestone. Sprinkle around somewhat to make it a thin layer to ensure it all converts soon.
An aquarium bubbler , or rather two, should be easy to plumb to a CO2 sensor. Just skip the water bath for one of them.
The calcium hydroxide is sold as "hydrated lime" and needs to just be stored isolated from CO2, and is mildly basic, so will slowly corrode your fingers (wash after touching, don't get any in your eyes).
Shouldn't even need gloves for this usecase, where one occasionally swaps the water and sediment for fresh stuff.
Btw, the waste, after soaking CO2, is just harmless limestone. Sprinkle around somewhat to make it a thin layer to ensure it all converts soon.