A barometer is a simple instrument for determining the pressure generated by the weight of the atmosphere. It can be used both for assisting in forecasting weather and for determining altitude. You can make your own weather predictions by following changes in barometic pressure.
1. Identify your type of barometer. Most personal barometers are “aneroid” while scientific ones are “mercury.”
2. Check to see whether there is an adjustment screw on the back of an aneroid barometer. Read your instructions to learn whether it is necessary to turn this screw to set your barometer to the current pressure reading.
3. Mount your barometer where it is easy to see and adjust.
4. Call the weather service, the airport or a news outlet to obtain a current barometric reading.
5. Turn the adjustment screw, if you need to do so, to set the barometer to the weather service barometer reading.
6. Check to see whether your personal barometer has two needles. Most have one that automatically follows the changes in atmospheric pressure while the other remains fixed until moved by hand.
7. Set the movable dial to coincide with the needle marking the current pressure.
8. Watch for the needle that follows pressure changes to move up or down from that fixed point. Tap the barometer lightly before taking a reading.
9. Compare readings to weather reports and other reports of barometric pressure to confirm the accuracy of your unit.