The Differences Between a Goniometer & a Protractor

A protractor cannot complete as many tasks as a goniometer.

The words protractor and goniometer are synonyms in many cases. Both devices can measure angles. However, the protractor is much more limited in its scope of applications. The goniometer comes in many different forms and performs a vast array of tasks that the simple protractor cannot.

Movement

The ability to move is one of the main differences between a protractor and a goniometer. A protractor is typically laid flat against a surface and measures the degree of the angles on that surface. A goniometer uses a stationary arm and a static arm, which measures range of motion (typically used in physical therapy).

Audio and Communication

The goniometer is also used for audio and communication applications. An audio goniometer measures the amount of stereo in a signal. A communication goniometer measures the angle of incoming radio messages. A protractor cannot measure audio signals.

Positioning

Also called a goniometer stage, a positioning goniometer is used when a device needs to be rotated in space around a fixed axis. A goniometer stage is primarily used for lasers and optical uses. The protractor can perform none of these tasks.

Surface Science

A contact goniometer is used to measure the angle at which a liquid/vapor interface meets a solid surface. Contact goniometers are also used to calculate surface tension. Originally, the contact goniometer used a microscope and an eyepiece. Today's contact goniometers use video cameras and software to analyze drop shape. A protractor cannot perform these tasks.

References

• Math Open Reference: Protractor
• The Pocket Goniometer: Applications - What is the Contact Angle?

Resources

• Pro Med Products Xpress