High Bandwidth Hybrid Magnetometer

Many applications of magnetic sensors require a wide frequency range. Established market is
TDEM (Time Domain Electro-Magnetics) used extensively in mineral prospecting and UXO
(unexploded ordinance) detection. New markets are opening associated with Electric Vehicle
Test, Occupational Health and Space Science; all require at least 100kHz bandwidth.
Currently fluxgates cover DC to 10Hz with induction coils covering a range from 1Hz to
100kHz, requiring two separate sensors. Furthermore, inductive sensors can be very large to
work at low frequencies making them difficult to use in the field.
Bartington Instruments (BI) plans a sensor that combines the 3-axis, DC capability of their
existing fluxgate technology with the bandwidth of an inductive sensor to address the needs
particularly of TDEM surveying but also the other emerging applications we have identified
which need a wideband sensor.
Innovation
Systems do exist which combine the two sensor types but these are bulky and expensive. BI
intends to make one compact instrument which integrates the technologies into a hybrid
sensor, small enough to be put down a deep borehole or moved round a test lab examining the
magnetic field generated by an electric car.
Technical problems in combining fluxgate and inductive sensing 'seamlessly' in a compact
hybrid sensor include magnetic coupling or interference, ensuring a smooth transition between
sensors and achieving a ‘best of both’ performance.
Key aims and objectives summary
• Meet all the requirements for current and future needs of the TDEM surveying
market.
• Provide sensors which can be used for field trials both for TDEM and other
applications
• Combine two technologies seamlessly into what appears as a single sensor.
• Combine the two technologies so that they do not interfere with each other to spoil
their individual or combined performance and retain accurate positional (vector) information.
• Produce a cost-effective unit which uses minimal power and space