On Sunday, December 7, 2014 10:16:45 AM UTC-8, Dave Nadler wrote:
How you sense the pressure is unimportant.

The pressure change between 0 and 1 feet MSL is much larger
than the pressure difference between 10,000 and 10,001 feet MSL.

Discuss amongst yourselves...

Looking at my decade old code for a transducer based variometer, I see that I went to a bit of trouble to convert pressure to ISA altitude before differentiating to get rate of climb. For even more amusement, consider the relationships between "altitude corrected" rate of climb, IAS, TAS, calculated total energy compensation, and speed to fly...

Marc