LOL. Don't hold back, Fred. Tell us how you really feel.

I agree that there are much better options today, but what I'm working on needs to support my old junky AFM too.

I did find the equations to calculate what the delta force on the flapper vane is when the density changes. Here is the relevant equation:

It's the equation for dynamic pressure as applied to a compressible fluid. (asciified of course - see the wiki entry for nicer pictures)

q = 1/2rpM^2

where:

q = pressure in Pascals

r = ratio of specific heats (1.4 for air @ sealevel- I haven't looked up creamy peanut butter yet)

p = static pressure in Pascals

M = Mach number

I'm still researching but it looks like the ratio of specific heats will change with air density so this is where the pressure will vary with density which varies with temperature.

So, using this equation I can calculate the pressure applied to the vane which multiplied the area of the vane will give the force on the vane. This of course in turn affects vane position as it works against the spring force. Note that I'm not actually trying to use all this math realtime in the ecu. I'm just trying to understand the physics to see how the AFM sensor responds in the real world.

Len