The 500C pulse oximeter is the deluxe version of the Amazon Zacurate 500DL Pro Series. It measures your SpO2 and pulse rate accurately and reliably and has a plethysmograph, alarm, and sound/alarm system. If the wave amplitude is low, this means that your blood perfusion is too low for reliable reads. The battery life is rated at 12 hours and the unit is rechargeable at 24 hours. For more information, visit www. pulseoxi the battery icon disappears after 2-3 blinks. If it remains on the OLED display, then it is an indication of a low battery level. The 500BL Pulse Oximeter 500C Elite is the most powerful pulse oximeter in the world.