Recording the heart beat of cattle using a differential system of optically pumped magnetometers

Sutter, Jens and Lewis, Oliver and Robinson, Clive and McMahon, Anthony and Boyce, Robert and Bragg, Rachel and Macrae, Alastair and Griffin, Paul and Riis, Erling and Ingleby, Stuart (2018) Recording the heart beat of cattle using a differential system of optically pumped magnetometers. In: Strathclyde Innovation Symposium on Optically Pumped Magnetometers, 2018-09-25 - 2018-09-26, Ross Priory.

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Livestock farming occupies about 30% of the Earth’s habitable surface area with a global value around £1 trillion. This important economic entity relies to a large extend on the health and wellbeing of the animals involved. Besides economic pressure there is also a growing interest of the consumer in the ethical keeping of livestock. Seeking physiological parameters that allow a close assessment of animal wellbeing has identified the animals’ heart beat as a possible parameter to monitor. The electric signal of the heart muscle excitation and relaxation does also carry a magnetic field component. Reading the magnetic field to query heart beat information does avoid the need for contact electrodes. We use two QuSpin Total Field Magnetometers (QTFM®) in a differential set-up to cancel common mode noise. Using the background noise to time-shift the two signals we optimize signal to noise ratio and record the magnetic heart signal over a noise floor close to 1 pT Hz-1/2 in the 1–100 Hz frequency band. By means of a correlation search algorithm we retrieve the heart rate and the shape of the magnetic heart excitation. Comparison to electro cardiograms shows good correlation.