FYS4250Fysisk institutt - Rikshospitalet

Image: Grimnes, Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts. ”A sensor is a mediator able to convert one or more measurands or physical variables into an equivalent signal variable of another type of quantity within a frame of a given unity” Pallàs-Areny, Webster, Sensors 2001 What is a sensor?

Image: Grimnes-Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts. - Sensor system: ”comprises the total signal path from the measurand to the observer and includes all sensing, conditioning and real-time processing elements in the path” - Electrode: ” An electrode is an electrochemical cell converting charge carriers from ions to electrons or vice versa. An electrode is only a half- sensor in the way that two electrodes are necessary in order to apply a current or read a potential difference in living tissue” - Probe: A ”probe is a broader concept than a sensor. A probe is often comprising multiparameter sensors (e.g. temperature) and may be held by the operator and be equipped with switches and level adjustment facilities. Example: Ultrasound probe” Source: Grimnes-Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts. More definitions....

FYS4250Fysisk institutt - Rikshospitalet Transducer - sensor (føler) - probe Position

Strain gages - Strain gages: ”are primarily displacement sensors based on variations in the electrical resistance of conductors or semiconductors as a function of mechanical stress” Image: Image: Grimnes, Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts.

FYS4250Fysisk institutt - Rikshospitalet Pressure- transducer Strain gauge: R=  L/A

FYS4250Fysisk institutt - Rikshospitalet Pressure- transducer Strain gauge: R=  L/A

Pressure transducer and Wheatstone bridge Image: Grimnes-Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts.

FYS4250Fysisk institutt - Rikshospitalet Force measurements

FYS4250Fysisk institutt - Rikshospitalet Force pressure Semiconductor transducer Piezoresistive

FYS4250Fysisk institutt - Rikshospitalet Plethysmograph = volummåler

FYS4250Fysisk institutt - Rikshospitalet Inductive displacement sensors L = n 2 Gμ

FYS4250Fysisk institutt - Rikshospitalet Linear Variable Differential Trafo (LVDT) sign problem

FYS4250Fysisk institutt - Rikshospitalet Position detection, capacitive sensor

FYS4250Fysisk institutt - Rikshospitalet Piezoelectric transducer C=εA/x

FYS4250Fysisk institutt - Rikshospitalet Step response

FYS4250Fysisk institutt - Rikshospitalet 2.order system

FYS4250Fysisk institutt - Rikshospitalet Temperature measurements, termocouple

Thermocouple Junction between metal A and B (hot junction), and an isothermal block with an ice bath temperature in connection to a voltmeter A change in temperature will result in a voltage change readable on the voltmeter Image: Grimnes-Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts.

FYS4250Fysisk institutt - Rikshospitalet Temperature measurement, termistor

FYS4250Fysisk institutt - Rikshospitalet Radiation thermometry Black body radiation Wiens law: λ m =2898/T [μm] Stefan-Boltzmann: W t =εσT 4 [W/cm 2 ]

FYS4250Fysisk institutt - Rikshospitalet Radiation thermometer

Infrared ear thermometer Image: Harsanyi, 2000, p 102

FYS4250Fysisk institutt - Rikshospitalet Fiberoptical thermometer, non-metallic

FYS4250Fysisk institutt - Rikshospitalet Optical instrument

FYS4250Fysisk institutt - Rikshospitalet Radiation sources

FYS4250Fysisk institutt - Rikshospitalet Light emitting diode (LED)

FYS4250Fysisk institutt - Rikshospitalet Fiberoptics Snells lov: n 2 sinθ 2 = n 1 sinθ 1

FYS4250Fysisk institutt - Rikshospitalet Photomultipliers

FYS4250Fysisk institutt - Rikshospitalet Diode as a light detector