BYM 501 E Fundamentals of Biomedical Engineering Bonded

BYM 501 E Fundamentals of Biomedical Engineering Bonded and Unbonded Strain Gauges Esat Can Şenel

OUTLINES Definition of Strain and Strain Gauges Bonded and Unbonded strain Gauges Working Area Mechanism of Use

What is strain? Strain is the response of a system to an applied stress.

What is a strain gauge? It is a RESISTOR that changes electrical strain into electrical resistor. Mechanical displacemen t Change of resistance

Bonded and Unbonded strain Gauges Unbonded Strain Gauges • • It consists Fixed and Movable Elements Metal wires connect frames together Bonded Strain Gauges • The wires are embedded into the diaphram.

Bonded and Unbonded strain Gauges Unbonded Strain Gauges Advantages : High Accuracy Disadvantages : More space is required Bonded Strain Gauges Advantages: Inexpensive Small Temperature dependence is less Very sensitive Disadvantages Susceptible to creep error

Working Mechanism Strain gauges can be glued on to the surface of the specimen Depending Material Elongates on the force: Resistor value changes

As the load (F) increases: i decreases R increases A decreases l increases

Wheatstone Bridge Under a great force, strain gauge and the specimen could deform permanently. To make more sensitive measurements, wheatstone bridges are used. They measure the degree of imbalance in the circuit. Quarter Bridge Strain Gauge Half Bridge Strain Gauge Full Bridge Strain Gauge

Working Mechanism

Area of Use

Area of Use Better positioning of patient bed in CT Insulin pump fluid flow monitoring Medical lift systems Mammography machines Kidney dialysis machines Medical robotics (Haptic feed back and force sensing)

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References https: //www. grc. nasa. gov/www/k-12/airplane/tunstraingage. html https: //www. robotics. org/content-detail. cfm/Industrial-Robotics-Tech. Papers/Understanding-the-Benefits-of-Strain-Gauge-Technology-in-OEM-Medical. Devices-and-Equipment/content_id/5962 https: //www. allaboutcircuits. com/textbook/direct-current/chpt-9/strain-gauges/ https: //www. sensordata-burster. com/the-benefits-of-strain-gauges-in-the-medicalindustry/ https: //automationforum. in/t/strain-gauge-principle-types-advantages-applications/4949 https: //automationforum. in/t/difference-between-bonded-and-unbonded-straingauge/4091 https: //www. sciencedirect. com/topics/engineering/strain-gauge