Barometers are scientific instruments used to measure atmospheric pressure. These measurements can help warn migraine sufferers of oncoming storms that may trigger a headache. Since atmospheric pressure changes depending on your altitude, you may need to reset your barometer after a move.
Acquire the current atmospheric pressure for your area from the local weather service or an online weather website. Make certain that the reading is recent, as pressure changes can occur quite rapidly and can cause an inaccurate resetting of your barometer.
Place the barometer upright on a flat and steady surface with the front of the device facing you.
Rotate the adjustment screw slowly with your screwdriver until you see the needle is level with the atmospheric pressure that you got from a weather service.
With increased altitude, barometers will become less accurate unless reconfigured to operate within their mid-range. Consult an expert if you wish to have a barometer calibrated for an elevation that is outside of its normal operating range.