Hmm, I’m computer, physics, mathematics guy and love to measure stuff … but not a great idea for keto.
At 10 am one day I had 0.4 mM and thought I dropped out of ketosis, but same day at 10 pm it was 1.3mM.
I found some papers where they measured ketones every hour through out the day. It goes up and down, up and down (3 am was the highest, I think 10am was the lowest…)
So it’s like chasing shadows. Don’t bother.
Same as measuring weight, over a month it’s meaningful but day by day, it can be disappointing for no good reason.
I found my belt buckle notches were going down but the scales stayed the same for few days.
The best thing to measure is grams of carbs consumed that day. Nail that and you’re 90% there.