How to adjust barometer?

Question

i have an aneroid barometer, when i try to set it, ill put it up to about 30 and it wont let me put it back down, no matter how much i take the s***w out. how do i fix this?

Answer 1

If you can't set it down then you have a mechanical fault in your barometer.

A barometer has to be adjusted for altitude. You write "30" so I assume you are American and use inches of mercury as unit. The average pressure is 1013 hectoPascal, or 29.9 Hg In in you country.

When you read the pressure from a weather chart, it is QFF, i.e. the pressure reduced to sea level according to a weekly or monthly variation in average temperature.

Aviators use QNH, which is the same but without compensation for temperature. When you come in your aircraft, you need to adjust your altimeter (which is actually a barometer) to the local pressure so that you will read the correct airfield elevation over the sea level. If you fly to a destination, the controller will give you the local QNH prior to landing so that you know your distance from the ground.

With a barometer at home, you do the opposite: you adjust it for your altitude over the sea and you keep it there. You don't read the altitude but the pressure.

The home barometer is just an indication if the pressure is above or under the average, which is what you want to know. If you don't adjust for altitude, you may be constantly reading a too low pressure.

When you get your mechanical problem solved, you must find from a weather map or other internet source what is the pressure compensated for sea level where you live. You turn the s***w to that value and keep it there.

I teach meteorology to aviators and I ask the following question: You flew yesterday and sat your altimeter to the correct airfield elevation: say, 100 ft above sea level. Today you come in your airplane and see that the elevation is 500 ft. Has the atmospheric pressure gone up or down since yesterday?

Think about an answer and you'll understand the principle of atmospheric pressure for the rest of your life.

Answer 2

I'm not sure you can "set" your barometer do anything.