Showing posts with label Week 6. Show all posts
How does pulse sensor works ??
How does the IR pulse sensor works ??
Principle of photoplethysmogram (PPG) Measurement !!
The pulse sensor is made using an infra-red emitter and detector. Light emitted by an infra-red emitter enters the skin and is diffusely scattered. The peak wavelength emitted by the emitter is typically in the range on 900nm < λ < 960nm. The detector placed on the other end captures a part of this diffused light. As light propagates through the tissues, a fraction of its intensity is absorbed by pulsating blood. Hence, when blood volume increases during the cardiac systole the captured intensity decreases creating a pulse-like photoplethysmogram (PPG) signal which reflects the blood volume changes in the arterioles. Furthermore, light absorptivity of haemoglobin (Hb) is significantly greater than that of oxyhemoglobin (HbO2) at 660nm. As arterial blood have high concentration of HbO2 and contrastingly, venous blood have high concentration of Hb, the sensor is able to detect the variation in both the systole and diastole stages.
Principle of photoplethysmogram (PPG) Measurement !!
The pulse sensor is made using an infra-red emitter and detector. Light emitted by an infra-red emitter enters the skin and is diffusely scattered. The peak wavelength emitted by the emitter is typically in the range on 900nm < λ < 960nm. The detector placed on the other end captures a part of this diffused light. As light propagates through the tissues, a fraction of its intensity is absorbed by pulsating blood. Hence, when blood volume increases during the cardiac systole the captured intensity decreases creating a pulse-like photoplethysmogram (PPG) signal which reflects the blood volume changes in the arterioles. Furthermore, light absorptivity of haemoglobin (Hb) is significantly greater than that of oxyhemoglobin (HbO2) at 660nm. As arterial blood have high concentration of HbO2 and contrastingly, venous blood have high concentration of Hb, the sensor is able to detect the variation in both the systole and diastole stages.
UPDATE: Week 6
This we we worked on filtering the signal form the heart beat sensor. The signal received from the sensor went through hardware filtering and now we want to accurately count the beats per minute. We started by trying to detect the peaks on the graph. On Processing we started by coding an array that received 200 data points. As each data point is spaced by 15 millisecond, we got readings from the sensor for 3 seconds. We determined the high and lows on this signal and removed everything that is above or below our range. This range were determined to be greater that 800 or less than 500. Anything that falls in this range is an error caused by moving the sensor and not the signal of heart beat as we wanted. We are getting close to accurate reading and the reading doesn't go too low and too high.
We also tested with a sensor form http://pulsesensor.com/. This is the sensor that works on the same principle as the designed sensor but is smaller in size as all the circuit is printed onto its back.
Finally we are working on the Final Lab Report draft. We are diving the work among each other and will combine and form the report.
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Week 6,
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