What method is used to detect blood volume pulse?

The method used to detect blood volume pulse is through a photoplethysmograph sensor. This type of sensor works by employing light to measure changes in blood volume within the microvascular bed of tissue. When blood vessels expand with each heartbeat, more light is absorbed and less is reflected back, which can be detected by the sensor. This technique is widely used in various applications, including assessing heart rate, blood circulation, and even estimating blood oxygen levels indirectly.

In contrast, an electrocardiograph sensor is primarily used to measure electrical activity of the heart rather than changes in blood volume. A pulse oximeter also uses light but is specifically designed to measure the saturation of oxygen in the blood rather than the volume pulse. A sphygmomanometer is utilized to measure blood pressure and does not provide information about blood volume pulse. Thus, the photoplethysmograph sensor is the most accurate and relevant tool for detecting blood volume pulse.