A versatile stretch sensor for measuring physiological movement using a centre loaded, end-supported load cell

Acquisition of movement of some body parts can provide important physiological information. In clinical practice as well as for research purposes different types of sensors such as piezoelectric crystals, conductive rubber and optical displacement sensors are used for such measurements. Each of these sensors is associated with its problems. This paper discusses the use of a stretch sensor constructed using a small metal bar, approximately the size of a zipper slider that can be sewn into a fabric in the form of a belt. A combination of elastic, and Velcro material attached to the metal bar, provides a sensor that is capable of linear, steady state measurement as well as rapid response detecting slow and fast movement of the target. Incorporating the sensor in an elastic belt, allows measurement of physiological movements such as respiratory chest movements, abdominal and limb movements. This paper also discusses the potential use of the novel stretch sensor in measuring change in calf circumference during different manoeuvres, making it a useful assessment tool for calf venous function.