A detecting system, a mobile electronic apparatus and a method for detecting a physiological characteristic thereof are provided. The mobile electronic apparatus includes a sensor unit, a PPG photoplethysmography (PPG) sensor, and a processing unit. The sensor unit has a first, second, and third sensing electrodes. The PPG sensor senses a PPG signal. The processing unit is coupled to the sensor unit and the PPG sensor. When the first and second sensing electrodes detect a voltage difference above a threshold, the PPG sensor is triggered to detect blood volume changes, and when the third sensing electrode is triggered to detect electrical activity of a heart between the first and third sensing electrodes, the PPG sensor is disabled by the processing unit.本發明提供一種移動電子設備、檢測系統以及生理特徵的檢測方法。移動電子設備包含感測器單元、光電容積圖 (photoplethysmography, PPG)感測器和處理單元。感測器單元具有第一、第二和第三感測電極。光電容積圖感測器感測光電容積圖信號。處理單元耦合到感測器單元和光電容積圖感測器上。當第一和第二感測電極檢測到大於閾值的電壓差時,觸發光電容積圖感測器以檢測血容量變化,並且當觸發第三感測電極來檢測第一感測電極與第三感測電極之間的心臟電活動時,由處理單元停用光電容積圖感測器。10‧‧‧主要結構100‧‧‧電子設備110‧‧‧感測器單元120‧‧‧光電容積圖感測器130‧‧‧處理單元PA、PB、PC‧‧‧電極
