PPG grayscale color wheel chart

Quick answer：

A PPG grayscale color wheel chart is a visual representation that uses a grayscale color wheel to depict the spectrum of photoplethysmography (PPG) signals. PPG is a non-invasive optical technique used to measure the pulse volume in the peripheral arteries. The chart typically shows the intensity of the PPG signal across different wavelengths, helping to analyze and interpret the data for various health and fitness applications.