An oximeter uses light-emitting diodes to transmit red and infrared light through a body part and detects the amount of light absorbed, allowing it to determine oxygen saturation levels in the blood. It works by measuring the differences in light absorption between oxygenated and deoxygenated hemoglobin, as oxygenated hemoglobin absorbs more infrared light while deoxygenated hemoglobin absorbs more red light. Reflectance pulse oximetry is an alternative that detects light reflected off the body rather than transmitted through it, making it usable on parts like the forehead and feet.

1. Resistive sensor application: Oximeter
 Types:
 Transmissive pulse oximetry
 Reflectance pulse oximetry
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A transmissive pulse oximetry
send a light ray from a diode
and measure the amount of
received light on the other end

2. Oximeter
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• One LED is red, with wavelength of 660 nm,
and the other is infrared with a wavelength of
940 nm.
• Absorption of light at these wavelengths differs
significantly between blood loaded with oxygen
and blood lacking oxygen.
• Oxygenated hemoglobin absorbs more infrared
light and allows more red light to pass through.
Deoxygenated hemoglobin allows more infrared
light to pass through and absorbs more red light.

3. 3
the device passes two wavelengths of light through the body part to a
photodetector. It measures the changing absorbance at each of
the wavelengths, allowing it to determine the absorbances due to the
pulsing arterial blood alone
where HbO2 is oxygenated hemoglobin (oxyhemoglobin) and Hb is
deoxygenated hemoglobin.

4.  Reflectance pulse oximetry is a less common alternative to
transmissive pulse oximetry.
 This method does not require a thin section of the person's
body and is therefore for feet, forehead, and chest, but it also
has some limitations.
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Resistive sensor application: Oximeter