Image Credit: OMEGA Engineering, Inc.
What are Gaussmeters?
Gaussmeters are scientific instruments that measure the strength and/or direction of a magnetic field. Typically, Gaussmeters measure a magnetic field or flux density in metric units of gauss (G) or the international system (IS) unit tesla (T).
Magnetometers and Gaussmeters are sometimes interchangeable names describing the same magnetic field instrument used to sense or measure a magnetic field. The two can be differentiated, however, based on their level of sensitivity. Gaussmeters are considered high strength measuring devices for fields above 1 milliTesla (mT), while magnetometers are used for high sensitivity applications below 1 mT.
Magnetism and Gaussmeters
Magnetism describes how, on a microscopic level, materials respond to an applied magnetic field. These magnetic fields surround magnetic materials and are detected by the force they exert on other magnetic materials and moving electric charges. Types of magnetism include ferromagnetism, ferrimagnetism, antiferromagnetism, paramagnetism, and diamagnetism.
Because magnetism varies by location and with differences in the Earth's magnetic field or magnetosphere, Gaussmeters are used to provide orientation, navigation, and leveling information. For example, combination compasses and Gaussmeters are used on satellites and aboard airplanes that map the local structure of the Earth's magnetic field. Navies use compasses and Gaussmeters to detect submarines under water. Surveyors can use these Gaussmeters to locate boundary stakes buried in the ground or hidden by vegetation.
When selecting Gaussmeters, buyers should consider the specific type of Gaussmeter technology, its form, its outputs and interfaces, and its design specifications.
There are two basic types of Gaussmeter technologies: Hall Effect and Magnetoresistive devices. Incorporating different methods to detect and measure magnetic fields, these two technologies can include various subtypes that vary based on construction.
- Hall Effect devices convert the energy stored in a magnetic field to an electrical signal by developing a voltage between the two edges of a current-carrying conductor whose faces are perpendicular to a magnetic field.
- Magnetodiodes are two-terminal Hall effect devices similar to a conventional bipolar diode. The voltage-current characteristic of a magnetodiode is sensitive to a magnetic field.
- Magnetotransistors consist of a bipolar transistor implemented on a semiconductor surface. They are three-pronged devices consisting of an emitter region, an elongated base region, and a collector region. The presence of a magnetic field in the base region creates a Hall effect voltage which produces a pulse on the transmission line.
- Magnetoresistive instruments measure electrical resistance as a function of the applied or ambient magnetic field.
Form can be an important factor in selecting a Gaussmeter, as it determines where a device can operate. A large number of Gaussmeters are handheld devices, meaning they are portable and can be carried or transported for field work. Some larger devices are desktop or standalone modules for fixed location use.
Outputs and Interfaces
Outputs and interfaces determine how a Gaussmeter displays and transfers information to the system or the user. Outputs include analog current, analog voltage, analog frequency, or digital. Interfaces include parallel, serial, switch, or USB.
Gaussmeters include a large array of design specifications which can be important to finding a device suitable for a given application.
- Sensing accuracy defines the reading accuracy that is required of the device.
- Resolution is the smallest increment of measurement possible with the device. A higher resolution denotes a device that can take more sensitive readings or can measure on a smaller scale.
- Bandwidth is the frequency range over which the device meets its accuracy specifications. Accuracy is degraded at lower and lower frequencies unless the device is capable of dc response, and at higher frequencies near resonance and beyond, where its output response rolls off. Frequencies in the database are usually the 3dB roll-off frequencies.
- Flux density measurement is the range through which the sensor or instrument is designed to measure, often corresponding to the linear output region of the sensing technology. Magnetic flux density is also known as magnetic field. It is measured in units of Gauss or Tesla (1 T = 1000 G).
- Operating temperature indicates the temperature range over which the device must operate.