biophys review final

fast response to changes in temp and widest temp range

why are thermocouples useful even though they require reference junction compensation?

linear relationship between resistance and temp and excellent accuracy

why are rtds generally more accurate than thermocouples?

high sensitivity, allowing precise measurements

why are thermistors useful for precision temp measurement over small ranges?

as distance decreases, capacitance increases

what happens to the capacitance of a microphone when the diaphragm moves closer to the backplate

have a permanently charged material so they don’t need external polarization

why does electret microphone consume less power than a MEMs microphone?

Piezoelectric sensing: generates V when mechanically stressed

piezoresistive sensing: changes electrical R when strained

what is the difference between the piezoelectric and piezoresistive sensing?

detect small resistance changes in strain gauges with high sensitive and help reduce noise and temp effects

why is a wheatstone bridge used with strain gauges?

inaccurate strain readings

what are the consequences of improper strain gauge placement?

depends on specific measurement spot size. at wrong distance, may include surrounding areas, causing wrong readings

why can IR thermometers give inaccurate results if used at the wrong distances?

avoid hydrostatic pressure errors, which can falsely read.

higher causes decrease in pressure and lower causes higher BP

why should blood pressure cuffs be positioned near heart level?

HR, blood oxygen sat, blood flow, respiration, oxygenation

what physiological signals can be measured using optical sensors?

blood oxygen saturation (spo2) and pulse rate

what does a pulse oximeter measure

converts transmitted or reflected ligh into an electrical signal

what is the role of the photodetector in a pulse oximeter?

changes in light absorption, reflection or transmission. non-invasive, fast and safe

what is an optical sensor and why are optical sensors useful in biomedical measurements?

detects blood flow. when weak, pulse signal becomes faint/inconsitent leading to no reading or inaccuracies

why can poor circulation reduce the accuracy of pulse oximetry?