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一、引言当我们试图测量弱小电生理信号时必须减小电噪声,尤其是减小从馈电线感应到患者身上的静电或电磁电位。理想情况下电生理测量应该在电干扰最小的房间内进行。可是,在必须进行龟生理测量的医院里并不总可以找到这样的房间。所以必须有另一种解决办法。有效地减小馈电线感应电噪声可以简单地通过将患者接地来达到,可是这是不足取的,因为这样患者更容易触电。为了增进用电安全,技术标准迫使我们废除几乎所有患者接地系统而采用患者隔离系统。这通常是在如图1的前置放大器中将患者与地隔离。这样,即使馈电线电位加到患者身上,电流也不会通过生理测量放大器流入大地。目前的隔离放大器由患者导联中的串联电阻和二极管来保护以不受
I. INTRODUCTION Electrical noise must be reduced when we try to measure weak electrophysiological signals. In particular, we reduce the electrostatic or electromagnetic potential that is sensed from the feeder to the patient. Ideally electrophysiological measurements should be performed in the room with the least electrical interference. However, such rooms are not always available in hospitals that must conduct turtle physiological measurements. So there must be another solution. Effectively Reducing Feeder Induced Electrical Noise can be achieved simply by grounding the patient, but this is not a good idea because it is easier for the patient to get an electric shock. In order to improve the safety of electricity, technical standards have forced us to abolish almost all patient grounding systems using patient isolation systems. This usually isolates the patient from the ground in the preamplifier of Figure 1. In this way, even if the feeder potential is applied to the patient, the current will not flow through the physiotherapy amplifier into the ground. Current isolation amplifiers are protected by series resistors and diodes in the patient leads