ashish s koujalgi

8/2/2019 Ashish S Koujalgi

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Sensors For Biomechanics



Introduction

o A sensor (also called detector) is a converterthat measures a physical quantity and convertsit into a signal which can be read by anobserver or by an (today mostly electronic)

instrument.o Sensors have a wide range of classification.

o Here, the topic of discussion is biosensor.

o In biomedicine and biotechnology, sensors

which detect analytes thanks to a biologicalcomponent, such as cells, protein, nucleic acidor biomimetic polymers, are called biosensors.



Various Types Of Sensors

Kinematics: Orientation, joint angles, velocity, acceleration.

Orientation/tilt

Tilt switch

Digital compass

Joint angles (rotary motion)

Goniometer

Electrogoniometers

Flex sensors

Demo project by 8th grader: sign language translationglove

Encoders



Potentiometers 3D Motion Capture

Velocity (translation)

Inertial Measurement Unit

Velocity (angular) Gyroscope

Encoders

Acceleration

Accelerometer



Kinetics: Forces and Torques

Force

Push/Contact

Scales (kitchen scale, bathroom scale)

Piezoelectric sensors (see Nike’s piezoelectric shoesensor tear down)

Force Sensing Resistors

Flexiforce pressure sensors

Digital force gauges

Load cells

Muscle force – EMG sensor



Pull/Stretch

Luggage scale

Spring scale

Digital force gauges

Load cells

Stretch sensors Torque Torque wrench? Just use Force and multiply by

distance!



Case Study : Pulse Sensor

A Piezo-electric transducer is used here, which convertsphysical activity such as changes in force or pressure intoan electrical signal. The applications are wide such as :o sensing and recording peripheral pulse in the finger;o

measuring carotid pulse;o recording throat excursions from swallowing;o monitoring Korotkoff sounds;o monitoring heart sounds;o use as a small-animal pulse and respiration transducer;o monitoring vibrations; and counting liquid drops for

titrations



Block Diagram



To use as a pulse transducer:

attach it to tip of any finger and lightly rest

finger on transducer surface with edge offinger slightly overlapping edge of transducerwrap around finger. If finger tip turns whiteor feels cold, then unit is too tight.



To measure carotid pulse:

place it on one of the carotid arteries, justbelow hyoid bone, and hold there .Useminimum tension needed to obtain anadequate signal; expect 40-60 mV.

To monitor swallowing:

place it on throat near base to one side ofthyroid cartilage; secure with elastic. Properlyplaced, should produce several hundred

millivolts during a swallow.



To monitor heart beat :

Secure it to chest with elastic webbing. Bestresults are obtained when its in direct contactwith the skin. The output of this transducer isconnected to an audio amplifier.



Ashish S Koujalgi1MS09IT012

Specifications Frequency response : 2.5 Hz to 5 KHz

Signal output : Varies with force: typical fingerpulse yields 20-40 mV, but can exceed 500 mV.

ashish s koujalgi

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