The Altimeter is a measuring instrument that indicates heights above sea level i.e. altitude. The altimeter houses an aneroid barometer which responds to small variations in atmospheric pressure. The changes of pressure that occur at different altitudes are indicated on the dial in terms of height above sea level.

Requirements: The best demonstration of the altimeter is the change in elevation when traveling between two different locations. You may also "zero" the altimeter before taking it to the classroom, and then measure the elevation of your school. The smallest division on the dial of the altimeter is 100 feet. Therefore, at most schools it would be difficult to measure the change of elevation in different locations on school property. However, the altimeter can also be used to measure the change in atmospheric pressure. This can be done at one location over time.

Manufacturer: Barigo Altimeter

Suggested Grade Levels: 6th and above

Suggested Courses: Earth Science, Environmental Science, Physics, Social Studies, Chemistry

Video Demonstration:

Directions:

To use as an altimeter:

1. Determine the local altitude of the starting point.

2. Set the hand on the dial to indicate this height by turning the adjustment ring.

3. The altimeter will then indicate any changes of elevation as you move from place to place. The most accurate readings are taken when the dial is in a horizontal position.

To use as a barometer:

1. The inner scale is used to measure atmospheric pressure. Average sea-level pressure is 29.921 inches or 101.325 kPa. Notice that when the needle is at 0 ft above sea level it is also at approximately 29.9 inches.

2. If you are taking atmospheric pressure measurement on the same day at different locations, the pressure will decrease as elevation increases.

3. In contrast, if the instrument is used at the same location but at different times, a change of atmospheric pressure correlates to weather conditions. Increasing atmospheric pressure indicates weather trending towards "fair weather" or clear and cool, while decreasing pressure indicates weather trending towards "bad weather" or storms and precipitation.

The outer scale is used for elevation, while the inner scale is the barometer.