Glossary term
Biosignal
Measurable physiological, biological, or biomechanical signal acquired from a living system for monitoring, diagnosis, therapy, or control.
Definition
quantityA biosignal is a measurable signal produced by a living system or by its interaction with a sensor.
Biosignals may be electrical, mechanical, optical, acoustic, thermal, chemical, or derived from images. Their engineering interpretation depends on anatomy, physiology, sensor interface, noise, motion artefacts, bandwidth, sampling, filtering, calibration, and the clinical or research question.
A biosignal is information-bearing variation measured from a living system. It may come directly from physiology, such as bioelectric activity, pressure, temperature, motion, flow, sound, or light absorption. It may also be derived from an interaction between a sensor and tissue, such as ultrasound echoes, optical scattering, impedance changes, or force response.
Biosignals are rarely ideal sources. They are affected by anatomy, sensor placement, tissue contact, motion, respiration, perfusion, temperature, electromagnetic interference, skin impedance, ambient light, cable movement, and algorithmic processing. A clean waveform is not automatically clinically meaningful, and a noisy waveform is not automatically useless if the relevant feature is still recoverable.
Engineering use
Biosignal engineering is used in electrocardiography, electroencephalography, electromyography, pulse oximetry, blood pressure measurement, respiration monitoring, ultrasound, imaging systems, gait analysis, neural interfaces, wearable sensors, and closed-loop medical devices.
The acquisition chain includes the measurand, transducer, analog front end, filtering, isolation, analog-to-digital conversion, timing, digital processing, display, storage, and validation. Each stage should preserve the feature that matters for the intended use while controlling artefacts and patient safety risks.
Common mistakes
A common mistake is designing the electronics around an ideal signal amplitude while ignoring the body interface. Motion artefact, electrode drying, optical path changes, cable strain, poor shielding, or poor timing can dominate the measurement. A strong biosignal review states physiological source, measurement site, expected range, bandwidth, sampling rate, noise sources, artefact controls, calibration method, validation data, and failure response.