I saw a light reaction method that takes 30 seconds and is accurate to 0.1ppm of CO2 over a wide range. Cost a lot though
But boy, it would solve many issues

I'm trying to see about getting one and a nice light DO probe model for the lab
Then I can borrow it for a few days myself

Drop checkers are not fast, just keep that in mind when using them, there is an assumption they are always correct, but the question is less that, but more when is it that they are measuring relative to the color?

The lag time is long.

Regards,
Tom Barr