Magnetic measurement tools attract attention

In one of the earliest magnetic measurements, primitive mariners used lodestones—magnetized pieces of magnetite—to determine the earth's magnetic field. Today, thousands of applications require the measurement of magnetic fields. For example, sensors in automobiles use the earth's magnetic field to help with navigation, and roadway sensors examine the magnetic signature of vehicles going by to determine the type of vehicle and its direction (figure). In another application, geologists and earth-science researchers can detect iron ore and other mineral anomalies by precisely mapping magnetic fields.

One of the primary military applications for magnetic-field measurement is the detection of submarines. For example, the submarine-hunting Orion P3C military aircraft has a long tail boom to house the magnetometer far away from the engines and other sources of interference. Other military uses for magnetic measurements include instrumentation of small-caliber shells in the development of ranging fuzes.

Countless other applications exist in the industrial, scientific, and medical fields. Industrial customers may simply need to verify the north and south poles on magnets used in motors. Paul Elliot, owner of Magnetic Sciences, a vendor of magnetic-field sensors, reports that installers of oil pipelines need to measure the pipes to ensure that no latent magnetism resides in the steel. Many industrial users must measure the field of a magnet to ensure that it has not lost its strength. Another industrial use is to verify whether shipping containers are emitting a magnetic field that is greater than the legal limit.

Scientific uses of magnetic measurements include disk-drive-read-head research. The behavior of material in intense magnetic fields is an area of active study, and it is often necessary to measure the intense field that resistive, room-temperature, and superconducting magnets produce during research.

Whatever your application, you'll find that measuring magnetic fields requires specialized sensors and a knowledge of physics and electronics. You can use a variety of instruments, including gaussmeters, teslameters, fluxmeters, and magnetometers, to measure magnetism, and prices for these units range from pennies to hundreds of thousands of dollars. You can learn which sensor fits your application by reading the full article in our sibling publication EDN.