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How does a barometer work

Posted on August 20 2015

HOW YOUR BAROMETER WORKS

A Barometer measures the atmospheric pressure. Stormy weather is usually associated with low pressure or a falling Barometer.

  • To use a Barometer you set the outside needle over the top of the inter needle.
  • After a few hours you would read the Barometer by tapping the glass with your finger, this helps set the inner needle, then you would note which direction the inner needle has moved.
  • If the needle moves to the right, that indicates higher pressure and good weather.
  • If needle moves to the left, that would indicate a fall in pressure and not so good weather. The Barometer is very handy instrument to help forecast the weather because you will see the change in pressure before you actually see the change in the weather.

SETTING UP YOUR BAROMETER

To get maximum sensitivity from a barometer it needs to be set for the elevation for which it will be used. Most Manufactures set their barometers for sea level applications. This is great if you live at an elevation close to sea level. However, if you live at an elevation grater than 2,000 feet, above sea level, then your barometer should be readjusted.

All barometers should have an adjustment screw somewhere, usually on the back. The common procedure is to turn the adjustment screw, while watching the indicator needle, until the correct atmospheric pressure is indicated on the face of the barometer. You can get the local barometric pressure from the TV or Radio Stations, or the local Weather Service. This is how most barometers are set.

However, adjusting a barometer for higher elevations using this procedure will not maximize its sensitivity.

Since Barometers work on atmospheric pressure, the higher you go, the more the barometer will indicate a lower pressure. This happens because the weight of the air decreases with altitude.

To compensate for this the adjustment screw on the back of the barometer has to be turned, sometimes several turns, to reset the pointer needle correctly.

This type of adjustment may bring the pointer back to read the correct barometric pressure but the indicator will be away from its mid range.

The greater the elevation the father away the needle will be from its midpoint.

The further away the pointer is from its mid point, the less sensitive and accurate the barometer will be.

Very few barometers are set for maximum sensitivity when used at 2,000 feet or higher.

To maximize the sensitivity of a barometer it must be adjusted to work in its mid range. The best way is to find the mid range is to turn the barometers adjustment screw in both directions until you find the approximate mid point, that is, the needle travel an equal distant from left to right.

This can be done at home but care must be taken. To do this usually requires the removal of the glass face and pulling off the pointer needle. Be very careful if you decide to do this. It is not very hard, but pulling the needle off can be tricky. After finding the mid point as describe above, carefully pull the needle off from it mounting stem, and then reposition it back onto the mounting stem, so that the needle points to the current atmospheric pressure. Adjusting your barometer this way will cause the barometer to be more sensitive and ultimately more accurate. When we sell you a barometer we always ask you your elevation. We do this so that we can set your barometer for that elevation, making sure you have an instrument that is maximized for sensitivity, and ultimately more accurate.

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