Terry McGee wrote: ↑Sun Mar 12, 2023 4:01 am . . . The digital flow meter you were looking at is based (if I understand correctly) on cooling effect of air flow over a heated sensor.
Yes, I've looked at 2 manufacturers, they describe how the MEMS sensors work. Forced convection.
Terry McGee wrote: ↑Sun Mar 12, 2023 4:01 amWhat happens to that cooling effect if we increase the pressure and the density of the air flowing through it? Do they talk about that in the specs?
Indirectly. The spec sheet claims a "pressure loss" of less than 1 kpa (that's 1/100th of 1 atmosphere).
So, with such a low-pressure-loss sensor, the change in pressure and density will be very tiny. No need to worry about huge pressure+volume+density changes.
Terry McGee wrote: ↑Sun Mar 12, 2023 4:01 amI imagine that at least its resistance to air flow is probably pretty low. Again, do they talk about that in the specs?
See above.
Terry McGee wrote: ↑Sun Mar 12, 2023 4:01 amI have been wondering if we should concentrate on measuring pressure rather than flow for our tests. I know Tunborough prefers flow, but if we could use calibrators to predict the relationship, the Manometer is non-intrusive and easy to use. But lets see where the journey takes us....
My understanding of the model-in-progress contributed by Tunborough is that each whistle has a "coefficient" (K, Cd, WR - cousins all). Honestly, that was my hunch at the start of this thread. However, thinking more, I came to believe a flow-dependance (descending Cd) would be reasonable. Big factor ? I don't know. Depends on how the flow model will be used. But, we observed direct measurements supporting that once the "shifted" tape was fixed.
My perspective is: We are so close . . .
We've got: reliable pressure measurements, a well-exercised test+data-collection protocol, willing analysts (on 3 continents !), and a model-in-progress. With a good flow sensor, we could have a very clear picture.
I mean, taking a step back, the existing flowmeters are kind of a blurry lens, but they have allowed plenty of progress. And, frankly, it's been fun trying to puzzle-out all the effects. Maybe they're "good enough" for hobby-hackers.
But, really, wouldn't it be nice ?
ps: the Amazon seller allows refunds for 30 days . . . my offer to cost-share still stands.