Hank I want to know more about the Anemometer please

[beananimal]

I tried to calculate the real air flow curve from the pressure curve by Bernouilli equation and so.
But I did neither liked nor believed my own results.

Then I went for a foul-proved test and blowed-up a big garbage bag several times (nominal 120 liter) and recorded the time. As a result I can say that from the minimum stable speed and it can be linear interpolated:
~3 liter per second at 25% of maximum pressure recorded (at 25% power at my dimmer)
~8 liter per second at 70% // 75% of maximum pressure recorded (at 50% power at my dimmer) .

From 50% to 100% power at my dimmer the fan speed increased, it got louder and it seemed like more power.  Also  the measured pressure still increased, but I had no change in filling time of my garbage bag. That means the air flow did not increase any more.

 I'll have to go and double check for leakages, because in real life roasting there is a clear difference visible in Artisan if my dimmer is on 50%, 75% or at full power.

[hankua]

Susan
Looks like you got air pressure sensor working?

[SusanJoM]

It's still a work in progress. 
The hardware works and the software works.
My programming still needs some work.

Unfortunately for demonstration purposes, I don't actually use the fan control during the roast.  It seems that it's only function for me is to tame the fan.   
And that confuses me a tad, since without changing the air controller setting even once during the roast, the indication is that the pressure is declining.  Chaff? I wondered, but no; it starts right at the beginning of the roast.
So, I'm messing with it periodically.

[beananimal]

Could you make an emty reference"roast" ?
Just recording the heating process to see the effect of changing air density with temperature?

[SusanJoM]

Do you mean just doing that roast from a few threads up without any beans?

[beananimal]

Did you have this effects at multiple roasts? repeatable?

... without beans there will be no drop at filling in...

My idea would be to heat up the Huky from cold to full temperature just without changing the fan power (maybe at 50% ?)
In the second step you could run the fan at full power and switch off the stove to cool it down.
This is to see if the measured flow seem to change somehow dependent from temperature.

[SusanJoM]

Like this?

[beananimal]

What I see is only the heating-up (?), but it correlates to my idea of physics.

The dynamic pressure ( acc. Bernoulli, ...) is related to the density of the medium, which is reverse proportional to absolute temperature. (and other side effects)
273°K + 17° = 290°K
273°K + 87° = 360°K
273°K +207° = 480°K
So the density is reduced to 290 / 480 = 60%, 360 / 480 = 75%,
which fits somehow to the reduction of air flow of "160 down to 130" on your plot.

But the decrease in your first plot is much more. So here some brainstorming:

Any leakage? Especially the lower end connection of your flexible plastic hose to the hot copper tube. Check at hot condition.

Really no chaff, or just less than expected? At my accidental try run this was more relevant than I expected

Could you also post a photo of your setup showing the path of the flexible hose

[SusanJoM]

Here is the picture of the mess. 

And a .png with the bottom of the graph that shows the rest of the plunge.

I'm sure there are lots of leaks and lots of ways this could be tweaked for the science, but for my purposes I'm quite done with it.   The only other thing I will do one day is to run the same tests on the perforated drum;  that's my real interest and I haven't gotten there yet.

[beananimal]

Hello Susan,

don't call it a mess 

I may not look as smart as you wish, but at least you solved the critical issue of slope of the flexible  hose perfectly:

It is not straigh upwards - to avoid to much hot air climbing to the phidget, and
the connection to the phidget is not downwards - to avoid potential condensating water driping  into the phidget.

So the syphon you built is a good basis to keep the phidget alive for a long time.

And you have it connected to Artisan to record the air pressure / air flow without pushing buttons - or forgeting it from time to time 

[hankua]

Looks like its working to me; how does the readings vary from the lowest settting to the highest?

With the actual vacuum readings, you can re-program the buttons to the lowest settings used to the highest ones and calculate the %.