GY-MAX30100(PURPLE)

It’s an optical sensor that derives its readings from emitting two wavelengths of light from two LEDs – a red and an infrared one – then measuring the absorbance of pulsing blood through a photo-detector.
This particular LED color combination is optimized for reading the data through the tip of one’s finger.
The signal is processed by a low-noise analog signal processing unit and communicated to the target MCU through the mikroBUS™ I2C interface.
Developers of end-user applications should note that the readings can be negatively impacted by excess motion and changes in temperature. Also, too much pressure can constrict capillary blood flow and therefore diminish the reliability of the data. A programmable INT pin is also available.