If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#20
|
|||
|
|||
Pressure & temperature
"Doug" wrote in message ups.com... The local altimeter measures the weight of the air above it. When temperature is higher, the air expands (less density), but it's the same amount of air in a taller column. The atmosphere expands you see and is not bound tightly by a blocade above (it is bound by gravity actually). Anyway another item of interest is what you are setting the altimeter to is "sealevel" barometric pressure. Imagine a hole in the ground and the altimeter is lowered to the bottom of the hole (at your airport). Of course they dont actually have a hole, they have another way of adjusting it. Standard barometric pressure at sealevel is about 29.92. If you fly an airplane with a manifold pressure guage, it gives the local "absolute" pressure (non-sealevel adjusted). Anyway consider these principals and your knowledge will expand. Standard pressure at sea level is 29.92 at 15 degrees C. The weight of the air contrary to what you wrote above does vary hence high and low pressure weather systems. With low pressure air rises up the column diverges at the top and then descends giving a high pressure somewhere else. with a high pressure, the air converges high up, descends and then diverges when it gets to the ground. The principle of the altimeter is that it works on pressure, and pressure is the force exerted by the air and one common force is weight. When the air is less dense there are fewer molecules, the mass of air is less and therefore the column of air weighs less, (mass x gravity) hence the lower pressure. when you understand these principles then you will understand a bit more about altimetry, weather systems, high pressure, low pressure and winds all of which are about the forces of air. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
H2O, O2, Nutrients, Temperature | Stewart Kissel | Soaring | 0 | January 27th 07 05:35 PM |
OT? National Gas Temperature Map | Dave | Piloting | 0 | January 21st 07 11:28 PM |
Outside air temperature probe | dlevy | Owning | 9 | November 7th 06 05:14 PM |
'Room Temperature' | Anthony | Home Built | 11 | August 23rd 04 07:36 PM |
temperature sensor | Philippe Vessaire | Home Built | 2 | March 3rd 04 03:37 AM |