How to get separate BPM readings from two pulse sensors using one Arduino
Change &quot;#define USE_ARDUINO_INTERRUPTS true&quot; to &quot;#define USE_ARDUINO_INTERRUPTS false&quot;.

If, instead, your Sketch does not use interrupts to read PulseSensor data, your Sketch must instead contain the following two lines, in order:
#define USE_ARDUINO_INTERRUPTS false
#include &lt;PulseSensorPlayground.h&gt;

Source: https://github.com/WorldFamousElectronics/PulseSensorPlayground/blob/master/src/PulseSensorPlayground.h