A goniometer is an instrument that either measures angle or allows an object to be rotated to a precise angular position. The term goniometry is derived from two Greek words, gonia, meaning angle and metron, meaning measure.
There are many types of goniometers, each specialised for its particular application.
An audio goniometer is used to see the amount of stereo in a signal.
Goniometers are used for direction finding
in signals intelligence
applications for military and civil purposes, e.g. interception of satellite and naval communications as performed on the French warship Dupuy de Lôme
uses multiple goniometers.
In crystallography, goniometers are used for measuring angles between crystal faces. They are also used in X-ray diffraction to rotate the samples. The groundbreaking investigations of physicist Max von Laue and cohorts into the atomic structure of crystals in 1912 involved a goniometer.
In occupational therapy
and physical therapy
, a goniometer is an instrument which measures an axis and range of motion. If a patient or client is suffering from decreased range of motion in a joint (i.e. a knee or elbow), the therapist can use a goniometer to assess what the range of motion is prior to intervention, and then make sure the intervention is working by using the goniometer in subsequent interventions.
In surface science
, an instrument generally called a contact angle goniometer is used to measure the contact angle
at which a liquid
interface meets a solid surface. The first contact angle goniometer was designed by Dr. William Zisman
of the United States Naval Research Laboratory
in Washington, DC
and manufactured by ramé-hart (now ramé-hart instrument company), New Jersey, USA. This tool is used not only for contact angle and surface energy
applications, but also to measure surface tension
using pendant drop
, sessile drop
, and other methods. The original manual contact angle goniometer used an eyepiece with microscope. The current generation of contact angle instruments uses cameras and software to capture and analyze the drop shape and are better suited for dynamic and advanced studies.
is used to measure the reflectivity of a surface at a variety of angles.
A positioning goniometer or goniometric stage is a device used to rotate an object precisely about a fixed axis in space. It is similar to a linear stage, however, rather than moving linearly with respect to its base, the stage platform rotates partially about a fixed axis above the mounting surface of the platform. Positioning goniometers typically use a worm drive with a partial worm wheel fixed to the underside of the stage platform meshing with a worm in the base. The worm may be rotated manually or by a motor as in automated positioning systems.
Knife and blade cutting edge angle measurement
The included cutting angles of all kinds of sharp edge blades is measured using a laser reflecting goniometer. Developed by CATRA
in the UK, a range of devices can accurately determine the cutting edge profile including a rounding of the tip to 1/2°. The included angle of a blade is important in controlling its cutting ability and edge strength, i.e a low angle makes the edge thin and optimized for cutting while a large angle makes it thick, which cuts poorly, but is very strong.