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Introduction
The human pulse can be measured optically. The blood pressure varying with the heart impact leads to an optically measurable change of the blood content of the peripheral containers. This lets itself detect e.g. well at the finger.
Two work on the project was to us at the disposal, which had so far progressed that the optically seized pulse signal on a LC-display could be plotted. Both work was realized with a micro CONTROLLER PIC16C74 for the collection and visualization of the measuring signal.
Pulse measurement in the transmitted light
As source of light a red, super+bright LED was used. The finger penetrating light with a light frequency converter TSL230 one detected. The period duration signal of the TSL230 using the Capture unit of the micro CONTROLLER with an accuracy by approx. 15 bits was seized. 50Hz of spurious signals were suppressed by digital filtering and the pulse signal was extracted.
Pulse measurement in reflection
For the lighting of the skin surface infrared was used an LED. The scattered back light was detected with a pin photodiode. Gleichlicht and spurious signals of high frequency were eliminated by a similar filter circuit. The pulse signal was digitized by a/D transducer of the micro CONTROLLER with 8-bits.
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