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Modern traffic flow sensor technologies
Published in Lawrence A. Klein, ITS Sensors and Architectures for Traffic Management and Connected Vehicles, 2017
The second type of magnetic field sensor is the magnetic detector, more properly referred to as an induction or search coil magnetometer. It detects the vehicle signature by measuring the distortion in the magnetic flux lines induced by the change in the Earth's magnetic field produced by a moving ferrous metal vehicle. These devices contain a single coil winding on a permeable magnetic material rod core. Like the fluxgate magnetometer, magnetic detectors generate a voltage when a ferromagnetic object perturbs the Earth's magnetic field. Most magnetic detectors do not detect stopped vehicles since they require a vehicle to be moving or otherwise changing its signature characteristics with respect to time. However, multiple units of some magnetic detectors can be installed and utilized with specialized signal processing software to generate vehicle presence data.
Rutherford and the Cavendish Laboratory
Published in Journal of the Royal Society of New Zealand, 2021
At the end of 1893 while still at Canterbury College, Rutherford began his physics research career with an investigation into the magnetisation of iron by high frequency discharges. He continued work in this area when he arrived in Cambridge and developed a magnetic detector for electromagnetic waves (Figure 2). In December 1895, he demonstrated the operation of the detector at a distance of 200 yards from a Hertzian spark transmitter. The first outdoor use of the detector occurred on 22 February 1896 when he set up a spark transmitter on Jesus Green and detected the radiated pulses at a distance of 350 yards in a house on Park Parade. On the following day, a successful transmission over a distance of nearly three quarters of a mile was achieved. Rutherford held the world record for the reception distance at the time. In the same year, however, Marconi came to England and developed a system for the transmission of Morse code signals by means of electromagnetic waves, the beginning of wireless telegraphy.
Rutherford's early life and work in New Zealand
Published in Journal of the Royal Society of New Zealand, 2021
In September, the Science Society held another Saturday night conversazione at the College. The large crowd thoroughly appreciated the Society's efforts. ‘Later in the evening a modification of Tesla's experiments on high potential currents was performed in the Chemical Lecture Theatre by Mr E Rutherford.’ Ern's magnetic detector of short current pulses wasn’t mentioned. It would have been extremely difficult to demonstrate it at these public events due to the sensitivity of the magnetometer to vibration.