Glossary

4½ Digit Display

This describes a digital display that can show five digits but the left-most digit can only display 0 or 1. This is the case for the Mag-01H, which can display values in the range 00,000 to 19,999.

Alignment Error

This is an error in alignment between the Z-axis fluxgate element and the mounting face of the sensor. The Z-axis fluxgate is in general aligned with the long axis of the sensor.

Analogue Output

This is the voltage range output by the sensor. It represents the measured magnetic field intensity. The output signals may be differential or single ended. For single ended sensors, the voltage is measured between the output channels (for example, X) and the signal ground. For differential sensors, the measurement is made between the two individual outputs channels (for example, +X  and -X).

Bandwidth and Frequency Response

The Bandwidth and Frequency Responses parameters correspond to the frequency range over which the sensor will provide a reading of magnetic field intensity.

Frequency Response is the frequency range over which the amplitude of the sensor’s output will be equal to the amplitude of the field applied (± 5%).

Bandwidth is the frequency range up to the -3dB point, where the amplitude of the sensor’s output is equal to ~70.1% of the field applied.

Note that the measurements of higher frequency field will still take place with reduced amplitude.

Current Consumption

This is the current drawn by the sensor from the power source for correct operation of the sensor.

Drone

See Unmanned Aerial Vehicle (UAV).

Excitation Breakthrough/Excitation Frequency

This is the amount of signal present on the sensor’s output at the excitation frequency of the fluxgate. The excitation frequency is several times the maximum bandwidth of the sensor. In order to achieve best performance, this excitation signal will need to be filtered out (in analogue or digitally).

Frequency Response

See Bandwidth and Frequency Response.

Geostationary Orbit (GEO)

This is an Earth-centred orbit with an altitude of around 35,786km. At this altitude, objects can match the rotation of Earth, therefore making them stationary relative to a point on the Earth surface. Many telecommunications satellites are in this orbit. Three such satellites working together can provide near-global coverage. Compare this with Low Earth Orbit (LEO).

Hysteresis

If the sensor is subjected to a magnetic field larger than the full scale range, then the core materials’ magnetization may be altered permanently. This can alter the quoted offset value.

ISO 7

ISO 7 Cleanroom Specifications, also known as Class 10000, is a standard for cleanrooms. Cleanrooms are used where particulate dust levels need to be very low, to avoid contamination during product manufacture. 

Linearity Error

This corresponds to the change in the scaling error over the full measuring range of the sensor.

Low Earth Orbit (LEO)

This is an Earth-centred orbit with an altitude in the range 160km to 1000km. Most artificial objects in space are in this orbit, such as the International Space Station. Compare this with Geostationary Orbit (GEO).

Magnetic Anomaly Detection (MAD)

This refers to magnetometers used to detect tiny variations in the Earth’s magnetic field, and in particular the use of magnetometers to detect submarines. Submarines necessarily include ferromagnetic material, which creates a detectable disturbance (anomaly) in the Earth’s magnetic field. Another application is aeromagnetic surveying.

Measurement Noise Floor

This is the underlying internal noise error of the instrument, measured by the residual field in a known zero Gauss chamber at 1Hz. It determines the smallest magnetic field, or field change, which can be measured by the sensor in optimum conditions.

Measuring Range

This is the maximum magnetic field intensity that the sensor can measure accurately.

Medium Earth Orbit (MEO)

This is an Earth-centred orbit between LEO and GEO. Most navigation satellites are in this orbit. Compare this with Geostationary Orbit (GEO) and Low Earth Orbit (LEO).

Mounting Face or Reference Face

This is the face onto which the sensor will be mounted when using the mounting points located on the sensor’s enclosure. Refer to the outline drawing for details of the mounting points.

Offset in Zero Field

This is the average value measured within a zero field.

Offset Temperature Coefficient

This is the change of offset value for a given temperature change.

Orthogonality Error

This is the error in angle between the three orthogonal fluxgates.

Output Impedance

This is the impedance of the sensor’s outputs. Sensors usually have relatively low output impedance.

Polarity

When pointing at Magnetic North, a positive value of magnetic field intensity will be measured by the sensor.

Power Supply Rejection Ratio

The ability of the sensor circuitry to suppress power supply variations. If changes beyond the threshold are present, power supply jumps will affect the sensor’s output and create noise.

Scaling Factor and Scaling Error

The voltage output of the sensor is related linearly to the field measured.

Scaling Factor (mV/uT) is a proportionality coefficient.

Scaling Error is the difference between the applied field and the measured field at a particular field intensity. It represents the difference between the perfect Scaling Factor (full scale range/full scale output) and the measured Scaling Factor.

Scaling Temperature Coefficient/Scaling Error

This is a scaling error dependent on temperature. It will therefore change according to the Scaling Temperature Coefficient when the temperature changes.

Single Sensor Axis to Body Alignment

This is the alignment error between the single sensor fluxgate and the ceramic cylindrical casing. This applies only to independent sensors.

Start-up Time

This is the time taken for the sensor to start operating after being switched on. See also Warm-up Time.

Supply Voltage

This is the voltage required from the power supply for operation of the sensor.

Unmanned Aerial Vehicle (UAV)

This is an aircraft piloted remotely or by an onboard computer. Commonly referred to as a drone.

Unmanned Underwater Vehicle (UUV)

This is a submarine piloted remotely or by an onboard computer.

Warm-up Time

This is the time required for the sensor to achieve its performance specifications. Scaling performance may be achieved in less time than  noise performance. See also Start-up Time.