Wednesday, 23 July 2014
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Tiny magnetic sensor tracks human heartbeat

Researchers from the German national metrology institute have used a miniature magnetic sensor developed at the US-based National Institute of Standards and Technology (NIST) to successfully track a human heartbeat.

The experiments were carried out at the Physikalisch Technische Bundesanstalt (PTB) in Berlin, Germany, in a building described as having the world’s best magnetic shielding − necessary to stop the Earth’s magnetic field and other external sources from interfering with the measurements taken by the NIST sensor.

The sensor − a tiny container of about 100 billion rubidium atoms in gas form, a low-power infrared laser, and optics − measured the heart’s magnetic signature in picoteslas.

In the experiments at PTB, the NIST sensor was placed 5mm above the left chest of a person lying face up on a bed, whereupon it successfully detected the weak but regular magnetic pattern of the heartbeat.

The same signals were recorded using the ’gold standard’ for magnetic measurements, a SQUID (superconducting quantum interference device). A comparison of the signals confirmed that the NIST mini-sensor correctly measured the heartbeat and identified many typical signal features.

The NIST mini-sensor generated more interference in the signal, but has the advantage of operating at room temperature, whereas SQUIDs work best at -269°C and require more complicated and expensive supporting apparatus.

The researchers suggest that NIST mini-sensors could be used to make magnetocardiograms, a supplement or alternative to electrocardiograms. Further tests of the NIST sensors at PTB are planned.

NIST’s miniature magnetic sensor is about the size of a sugar cube. The lid has been removed to show the inner square cell, which contains a gas of rubidium atoms. The diagonal bar is an electrical connection to the cell’s heaters, which are powered by th

NIST’s miniature magnetic sensor is about the size of a sugar cube. The lid has been removed to show the inner square cell, which contains a gas of rubidium atoms. The diagonal bar is an electrical connection to the cell’s heaters, which are powered by the red, black and white electrical wires. The clear optical fibre extending from the middle bottom of the sensor connects to a control box


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