Knife Edge Oriface in VSI Metering Unit
 

Hi,
I am hung up on the k.e.o. part of the metering unit. I understand that it compensates for laminar flow in the capilliary allowing the vsi to correctly show altitude change at all densities/temperatures, and it somehow uses turbulent flow to do this.
My difficulty is with the turbulent flow part - I see the oriface as simply another opening in the case that would allow more airflow.
Can anyone give me an explanation?!:ugh: