On Sunday, December 7, 2014 12:55:57 PM UTC-5, wrote:
What you have described is generally correct for FLOW
type variometers such as mechanical instruments and early
electric instruments.

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...