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Applications of Resistive Transducers in Biomedical Instrumentation

Applications of Resistive Potentiometer

Caliper Myograph

It measures change in displacement at various applications. One such application is to detect the changes in the chest (Thoracic) circumference. It operates by connecting a rotary potentiometer to a chest band on a person. In this setup, the transducer acts as a pivot to the caliper arms. They attach to the muscles as shown in the figure below. Therefore, now when there is a contraction of muscles, it makes the arm driven apart. Finally, the potentiometer measures the motions of the arm.caliper myograph

Spirometer

Spirometer is a device used for studying respiratory functions. It has a water tank, bell jar immersed upside down inside water and an external tube connecting the mouthpiece. One end of the string connects the bell jar and another to weight via a pulley. The subject breathes air to the tube-using mouthpiece. For every cycle of inspiration and expiration, bell jar moves up and down. The jar movement depends on the volume of air exhaled or inhaled. Accordingly, the weight attached on another side of the string also moves up and down. Pen recorder draws the output continuously resulting in a graph called Kymograph. In this device, a potentiometer mounted on the axis of the pulley measures the movement of the bell-jar. kymograph

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Applications of Resistive Transducers in Biomedical Instrumentation

Tremor Detection of Parkinson’s Detection

A miniature low-torque potentiometer detects the tremor in patients’ diagnosed with Parkinson’s disease. Two rods get attached to the hand and lower arm, to detect the flexion and extension of the patient’s wrist. One rod connects the rotor and another to potentiometer body. The setup is supplied with 1.4V using mercury battery. This detects the 0 - 10 degree tremor at 3 - 6 Hz and recorded. The recorded values used to evaluate drug therapy.

Applications of Strain Gauge

Applications of Photoelectric Type Resistive Transducers

Photoresistor or LDR uses transmittance method to measure the pulsatile blood volume changes. A small lamp and photoresistor are placed inside a box, which can be worn on the fingertip. The entire setup acts a bridge circuit. Along one of the bridge arm, the LDR is fastened. The resistance of the photoresistor is proportional to the light intensity that falls on it. The photoresistor is made of semiconductor material. So, when light falls on the LDR, resistance decreases. The bridge output varies based on the intensity of transmitted light. In our body, when heart muscle contracts, blood flow in finger increases. This results in a change of optical density in the finger. As optical density varies, the amount of light being transmitted through finger decreases. The resistance of photoresistor gets increased. resistive transducers I am M.Vidya, currently employed as Assistant Professor, Department of Instrumentation and Control Engineering, Coimbatore Tamilnadu,. I have completed my B.Tech Electronics and Instrumentation. M.Tech in Biomedical Engineering. I am passionate about Teaching and Research in the field of Biomedical Instrumentation and Biomedical Imaging. You can contact me at [email protected] for any technical queries.


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