On Wednesday, April 17, 2019 at 8:16:41 PM UTC-4, Deming Gray wrote:
I learned about a mini variometer that purports to have zero time lag...

Zero lag? For a hang-glider, sure, but... You might want to read:
http://www.nadler.com/sn10/Brozel_TE...n_20020510.pdf

Of course, a usable super-fast vario is possible, but not that way...
Back to the lab now ;-)