I just bought a Kestral 4000. Reading the instructions left me with a Question, If I don't input a barometric pressure or an altitude, will I still get an accurate density altitude reading?
Thanks, Mike
I leave the altitude on my Kestrel 4500 set to 0 so that I get a 'station pressure' reading; I don't even mess with barometric pressure for ballistic use and the DA output is still correct. As long as I have my ballistics software set to station pressure as well everything is good.
I don't have my Kestrel here to verify what I'm about to say by experimenting with entering various reference altitudes, but as I understand it DA converts your current air density (which the Kestrel computes from temp/pressure/humidity) to a relative altitude from a reference atmosphere. Your Kestrel should give you a good DA reading regardless of how you setup your barometric pressure or altitude.
There was a related question as to how the Kestrel calculated the air density (based off altitude tables vs actually calculated) but the fine folks at Kestrel have obviously thought this through much more than I have. According to them, DA is calculated from the absolute values of station pressure, relative to humidity and temperature. It is not affected at all by reference values entered in either BP or ALT settings. (see pg 17 of your instruction manual)
