Measuring Altitude

This monograph shows you how to build a very basic but highly accurate barometric altimeter. It covers the theory behind how it works and what its limitations are. It shows how to interface a pressure sensor with a microcontroller and the calculations required to determine altitude. Software for the MSP430FR4133 microcontroller by Texas Instruments is described in detail.

This is a very accurate altimeter. Here are some things you can do with it.

• You can put it at your feet, zero it out, and then lift it up to the top of your head and it will show you your height to within the nearest foot.


• If you live in a two story house you can take it from the first to the second floor and look at the elevation change.


• Sometimes on the summit of a mountain there is some ambiguity as to where the high point is. This altimeter may be able to resolve that ambiguity.


• If you have this altimeter in a car and you roll the window down while the car is moving you will immediately see the pressure drop due to the partial vacuum created inside the car by the flow of air past the open window.


• With the window closed you can watch the change in pressure when the car accelerates due to localized changes in air density inside the car.


• Have you ever wondered what the elevation difference is between the top of your driveway and the road? This sensor can tell you that.