This application note provides a method to make an analog front-end plethysmograph based on the TS507. A plethysmograph is an instrument for measuring changes in volume within an organ or whole body, usually resulting from fluctuations in the amount of blood or air it contains. In this context, we refer in particular to the fluctuations in the quantity of blood in blood vessels.
This document details the design of a demonstration board intended for educational and scientific purposes to measure changes in volume within an organ or body, specifically fluctuations in blood quantity. The system utilizes an optoelectronic plethysmograph method, employing an infrared light emitter and a phototransistor to detect light absorption by hemoglobin.
| Light emitter wavelength | 800 nm |
|---|---|
| Light receiver type | NPN phototransistor |
| Power supply voltage | 3.3 V |
| Reference voltage | 1.65 V |
| Amplification factor | 100 |
| Low-pass filter cutoff | 10 Hz |
No, the demonstration board is designed for demonstration purposes only and shall not be used as a medical instrument.
The sensor consists of an infrared light emitter diode (SFH309FA) and an NPN phototransistor light receiver (SFH487).
The analog front-end uses two high-precision rail-to-rail operational amplifiers, specifically the TS507.