How to Calibrate a Homemade Barometer

All barometers, not just homemade, must be set based on air pressure readings given by local weather stations.

Most homemade barometers are either "coffee can" or "simple water" barometers. Coffee can barometers stretch a balloon over the top of a can, attach a straw, lengthwise, to the center of the balloon, and attach a pin to the straw end. The pin levitates as air pressure increases and drops as air pressure decreases. Simple water barometers use a stopper to hold a straw upright in a larger bottle of water. Atmospheric pressure increases cause the water level in the straw to fall. Atmospheric pressure decreases cause the water level to rise. Here, we discuss calibrating both.

Things You'll Need

• Homemade barometer
• Pen and paper for scale

Instructions

Coffee Can Barometer

1. Monitor where the pin is pointing. Create a scale using a piece of paper with regularly marked lines, placed adjacent to the coffee can barometer. Mark daily the location of the end of the pin. Measure the height of the location, in centimeters, above the bottom of the coffee can.

2. Compare the numerical values of the height of the pin with readings given by weather stations. Mark official barometric readings next to pin heights.

3. Repeat Steps 1 and 2 until you have a scale reliably linking pin height to atmospheric pressure.

Calibrating a simple water barometer

1. Record the levels of water as they rise or fall in the straw. Mark them on the straw or create a scale adjacent to the straw.

2. Compare water levels to readings of atmospheric pressure provided by local weather services. Mark atmospheric pressure readings on the scale.

3. Repeat Steps 1 and 2 over a period of weeks until you have a scale linking water height to atmospheric pressure.

Tips & Warnings

• Make your barometer when the air pressure is at about the middle of its range (neither too wet or stormy -- low pressure -- or sunny and still -- high pressure). If you construct it when the air pressure is at the middle of its range, and the water starts at about the middle, then the water will have plenty of room to move as air pressure readings change -- fostering the accuracy of your calibration.

• Place your barometers outside: that's where you will best note changes in atmospheric pressure, fostering accurate calibration.

References

• Home Weather Stations Guide: Ever Wanted to Make Your Own Barometer?
• Starry Skies: Make Your Own Barometer!