摘 要： 便攜式動(dòng)態(tài)心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)" title="心電信號(hào)">心電信號(hào)采集器" title="數(shù)據(jù)采集器">數(shù)據(jù)采集器是現(xiàn)代動(dòng)態(tài)心電圖分析系統(tǒng)的重要組成設(shè)備。介紹以單片機(jī)為核心的智能心電數(shù)據(jù)采集系統(tǒng)的原理，詳細(xì)論述了硬件設(shè)計(jì)的要點(diǎn)及數(shù)據(jù)預(yù)處理軟件的有關(guān)算法。
關(guān)鍵詞： 單片機(jī) 心電信號(hào) 數(shù)據(jù)采集
心電圖是心臟疾病診斷的重要工具之一，然而在臨床中一些心臟病患者在短時(shí)間內(nèi)其心電圖并無(wú)異常。這樣就要花相當(dāng)長(zhǎng)的時(shí)間在醫(yī)院中作觀察診斷，從而給病人和醫(yī)院都造成了不必要的麻煩。為此，動(dòng)態(tài)心電圖分析處理系統(tǒng)便應(yīng)運(yùn)而生，該系統(tǒng)可以分為兩大部分，一是攜帶在被檢查者身上的袖珍心電圖信號(hào)采集器，另一為由微機(jī)系統(tǒng)組成的心電圖處理診斷系統(tǒng)。被檢查者配帶了心電圖數(shù)據(jù)采集器后可離開(kāi)醫(yī)院，其一天的動(dòng)態(tài)心電信號(hào)由采集器記錄下來(lái)，然后交院方將記錄的數(shù)據(jù)回送微機(jī)心電圖處理系統(tǒng)中進(jìn)行分析，作出正確的診斷。目前此類(lèi)系統(tǒng)大多為歐美產(chǎn)品，價(jià)格昂貴，國(guó)內(nèi)的研究尚處在起步階段。由于所需存儲(chǔ)的信息量大，目前的典型產(chǎn)品大多采用高精度的盒式磁帶機(jī)作為數(shù)據(jù)記錄盒。從原理上來(lái)說(shuō)，不可避免地存在磁頭的機(jī)械磨損問(wèn)題。同時(shí)，磁頭的清潔度、機(jī)械振動(dòng)及走帶的穩(wěn)定性都會(huì)影響心電信號(hào)記錄的準(zhǔn)確性。另外，將磁帶上記錄的數(shù)據(jù)回送微機(jī)系統(tǒng)時(shí)，還需專(zhuān)用設(shè)備，其回送的速度相對(duì)也較慢。隨著單片機(jī)技術(shù)的發(fā)展，特別是超大容量存儲(chǔ)器的出現(xiàn)，我們采用以單片機(jī)為核心，擴(kuò)充大容量數(shù)據(jù)存儲(chǔ)器的方式，徹底彌補(bǔ)了由磁帶式數(shù)據(jù)記錄器造成的上述不足。
1 心電數(shù)據(jù)采集器的硬件設(shè)計(jì)
1.1 基本硬件結(jié)構(gòu)
心電數(shù)據(jù)采集器的整個(gè)電路主要包括心電信號(hào)放大電路、模數(shù)轉(zhuǎn)換器、外接實(shí)時(shí)時(shí)鐘、單片機(jī)、程序存儲(chǔ)器、數(shù)據(jù)存儲(chǔ)器、與IBM PC的并行通訊接口等。其基本原結(jié)構(gòu)如圖1所示。
采集器采集的信號(hào)為雙通道心電信號(hào)。大容量數(shù)據(jù)存儲(chǔ)器擴(kuò)展采用端口擴(kuò)展譯碼。關(guān)于輸入過(guò)載保護(hù)、采樣、A/D轉(zhuǎn)換、與 IBM PC并行通訊、外接實(shí)時(shí)時(shí)鐘等問(wèn)題已有相當(dāng)多的文獻(xiàn)作了介紹，本文不再詳述。下面主要就心電信號(hào)的專(zhuān)用放大電路和心電數(shù)據(jù)采集系統(tǒng)的動(dòng)態(tài)校零技術(shù)進(jìn)行論述。
1.2 輸入信號(hào)放大電路
該心電數(shù)據(jù)采集器的二組差動(dòng)輸入信號(hào)是通過(guò)電極取自人體表皮的緩變微弱信號(hào)，其值不超過(guò)5mV。我們采用二級(jí)放大器構(gòu)成放大電路，其結(jié)構(gòu)如圖2所示。
第一級(jí)由A1、A2和A3組成同相并聯(lián)差動(dòng)運(yùn)算放大電路。為了取得最佳的低頻響應(yīng)，必須將該級(jí)的輸入端直接耦合到電極上，因此我們將該級(jí)的增益設(shè)計(jì)得較低，以減小該級(jí)的輸入偏流，避免使電極極化產(chǎn)生高壓。A1、A2組成同相差動(dòng)帶增益的電壓跟隨器，大大提高了電路的輸入阻抗，它對(duì)共模信號(hào)有很高的抑制比，對(duì)差模信號(hào)的放大倍數(shù)為：
A3為一獨(dú)立的差動(dòng)式放大器，調(diào)節(jié)Rf可使電阻對(duì)稱，減小誤差，進(jìn)一步提高共模抑制比。通過(guò)計(jì)算可得第一級(jí)的綜合放大倍數(shù)為:
第二級(jí)由A4形成同相比例放大電路，其放大倍數(shù)為32。
二級(jí)放大總的增益為800。由于心電信號(hào)的頻率范圍要求放大器具有0.04～150Hz的帶寬，所以利用第二級(jí)放大器A4，通過(guò)C1和C2組成了有源帶通濾波電路，以抑制干擾。
放大電路中另一個(gè)值得注意的問(wèn)題是當(dāng)異聯(lián)電極換接時(shí)，由于C1的作用可能會(huì)引起放大器的輸出飽和。因此在電路中加入電子開(kāi)關(guān)S0，當(dāng)放大器輸出飽和時(shí)，通過(guò)比較器自動(dòng)驅(qū)動(dòng)S0瞬時(shí)接通，C1迅速充電，從而使輸出脫離飽和狀態(tài)。
在該放大電路的設(shè)計(jì)中，雖然可使用常規(guī)低偏流運(yùn)放，但從實(shí)際出發(fā)，我們優(yōu)先選用單電源運(yùn)放，如F3140。由于其輸入級(jí)差分電路采用了PMOS器件，使它的輸入電阻可高達(dá)1.5兆歐，具有極低的輸入失調(diào)電流、電壓，并且可省去調(diào)零電路和外接偏置電阻，使整個(gè)放大電路變得更為緊湊，調(diào)試更為方便，也降低了功耗。
1.3 心電數(shù)據(jù)采集器的動(dòng)態(tài)校零
輸入級(jí)電路雖然采用了具有補(bǔ)償及自動(dòng)調(diào)零的運(yùn)放電路，但并不能完全克服放大器的零點(diǎn)漂移。當(dāng)設(shè)備連續(xù)工作時(shí)其影響尤為明顯。因此，在心電數(shù)據(jù)采集的硬件設(shè)計(jì)時(shí)，我們還采用了動(dòng)態(tài)校零技術(shù)，取得了良好的效果。使用該技術(shù)，在硬件電路上只需作簡(jiǎn)單的改動(dòng)，即用兩個(gè)同步工作的模擬電子開(kāi)關(guān)，如AH5012連接在輸入端與放大器之間，如圖3所示。
以A通道為例，每次正式采樣前，先由CPU發(fā)出校零控制信號(hào)，使S1斷開(kāi)，S2接通。接著讀入“零”位信號(hào)得V0, 并將其存入零位值寄存單元。然后復(fù)位校零控制信號(hào)，即使S1接通，S2斷開(kāi)，采樣讀入迭加了“零”位信號(hào)的心電信號(hào)數(shù)據(jù)VA0,顯然實(shí)際的信號(hào)采樣值即為：
VA＝VAo－V0 (4)
對(duì)于模擬電子開(kāi)關(guān)導(dǎo)通電阻引起的“零”位讀數(shù)偏差，由于它是一個(gè)穩(wěn)定的常量，可以通過(guò)實(shí)驗(yàn)分析，由軟件編程進(jìn)一步予以消除。
2 系統(tǒng)應(yīng)用軟件設(shè)計(jì)
2.1 軟件總體結(jié)構(gòu)
整個(gè)心電數(shù)據(jù)采集器的軟件采用模塊化結(jié)構(gòu)，以便于維護(hù)和擴(kuò)充。該軟件主要包括初始化、動(dòng)態(tài)校零、采樣、并行通訊管理、WDT等常規(guī)模塊，還包括心電信號(hào)數(shù)據(jù)預(yù)處理的專(zhuān)用濾波軟件模塊，如50Hz交流干擾濾波及漂移濾波等。系統(tǒng)程序流程圖如圖4所示。
2.2 交流干擾濾波算法
考慮到采集器攜帶者可能接觸的環(huán)境因素，在采集到的心電信號(hào)數(shù)據(jù)中必然會(huì)存在一定的50Hz工頻干擾信號(hào)。鑒于心電信號(hào)的頻譜主要在0.5～100Hz范圍內(nèi)，因此不能采用常規(guī)的平均濾波或點(diǎn)阻濾波算法。為此，我們選用了適用于心電信號(hào)數(shù)據(jù)的“增量預(yù)估”濾波算法。此算法主要原理是通過(guò)三角恒等式和一些采樣數(shù)據(jù)，估算出正弦波出現(xiàn)的幅值，經(jīng)過(guò)計(jì)算判斷該交流信號(hào)是否存在于采樣信號(hào)中，如有則減去，使實(shí)際心電圖信號(hào)保存下來(lái)。顯然，正確預(yù)估50Hz正弦信號(hào)的幅值是整個(gè)算法的關(guān)鍵。其主要依據(jù)是利用三角恒等式：
SIN(θ+δ)＝2SINθCOSδ－SIN(θ－δ) (5)
式中：θ＝2πfkt；δ＝2πft；
f＝50Hz；k＝0,1，.....
可以認(rèn)為δ表示工頻正弦干擾信號(hào)在一個(gè)采樣周期內(nèi)的相位變化。由式5可從兩次采樣(相位為θ 和θ－δ)的干擾幅值預(yù)估出下一次采樣時(shí)( 相位為(θ+δ)的正弦波干擾信號(hào)幅值。將式5乘以振幅可得50Hz
工頻干擾的差分方程：
DK+1＝2DKCOS(2πft)－DK－1 (6)
式中DK為交流干擾幅值序列，T為采樣周期。
為了在遞推算法中不斷修正預(yù)估值與實(shí)際干擾值的偏差，我們作誤差估計(jì)函數(shù)
F＝(AK－DK)－(AK－1－DK－1) (7)
式中，AK為可能包含交流干擾的實(shí)際采樣值。由于在兩次采樣間隔內(nèi)，AK 與AK－1是十分接近的，從而由式7可知，在算法的初始階段如果DK估計(jì)過(guò)大，則F趨于較大的負(fù)值；反之F趨于較大的正值。當(dāng)F接近于零時(shí)，說(shuō)明交流干擾信號(hào)的預(yù)估值接近實(shí)際值。因此在濾波程序中，通過(guò)判斷F的大小就可確定在DK上加上或減去其修正值Δd。當(dāng)然要適當(dāng)選擇Δd，如果Δd 取得太小會(huì)影響算法的收斂速度，而太大會(huì)造成振蕩。初始干擾幅度我們選為0.2mV。
2.3 漂移濾波算法
在心電信號(hào)數(shù)據(jù)采集過(guò)程中，由于許多因素(如電極或皮膚的張力)都可能引起緩慢的偏置漂移。目前根據(jù)歐美的標(biāo)準(zhǔn)，要求心電圖輸入設(shè)備至少有3.2秒的時(shí)間常數(shù)，這樣會(huì)進(jìn)一步加重漂移的影響。為此我們仿照克服漂移的經(jīng)典的模擬濾波器，經(jīng)離散化后得到了漂移濾波算式，實(shí)用后取得了滿意的結(jié)果。模擬濾波器的傳遞函數(shù)為：
式中，τ＝1.024s
對(duì)式8求Z變換得
對(duì)應(yīng)的差分方程為：
由式9不難編制相應(yīng)的濾波程序。
應(yīng)用單片機(jī)實(shí)現(xiàn)的心電數(shù)據(jù)采集器可以取代目前進(jìn)口的高精度盒式數(shù)據(jù)記錄盒，并且可省略數(shù)據(jù)回送裝置，從而大大降低成本。它克服了磁帶式記錄器設(shè)計(jì)原理上的缺陷，通過(guò)硬件和軟件所采用的有關(guān)技術(shù)，顯著地改善了所采集的心電圖信號(hào)的品質(zhì)。實(shí)踐表明該智能心電數(shù)據(jù)采集器運(yùn)行穩(wěn)定，能耗低，具有良好的應(yīng)用前景。
參考文獻(xiàn)
1 任德官主編.過(guò)程控制系統(tǒng)微機(jī)接口技術(shù).東南大學(xué)出版社，1992
2 沈蘭蓀著.數(shù)據(jù)采集與處理.能源出版社，1987
3 涂時(shí)亮.單片機(jī)軟件設(shè)計(jì)技術(shù).科學(xué)技術(shù)出版社,1988
4 David W.Mortara.Computers in Cardiology,1977