根据对金属接触式水温水位传感器结垢成因的分析，提出在传感器两端注入对称交流信号抑制水垢形成的方法。介绍了一种基于ATmega48 低成本、高性能的太阳能热水器防垢水温水位测控仪的设计。通过对测量噪声的分析，建立“白噪声+工频干扰”的噪声模型。 针对这种噪声，运用过采样和求均值的方法提高ADC 有效分辨率和改善信噪比，并给出一 种抑制工频干扰的方法。关键词：太阳能热水器；水垢；噪声；过采样；水温水位Abstract：In the first place, according to analyzing the causes of formation scale of metalcontiguous water temperature and level sensor that a method presented by adopting symmetrical AC signal in this paper. This paper introduces a prevent scale design circuit of water temperature and level of solar energy heater based on ATmega48, which is of lower cost and higher performance. Another innovative consideration here is, what’s more, that system noises can be modeled white noise & power line interference from the analysis of noises and interferences in the system. Last but not least, this paper describes utilizing oversampling and averaging to increase the resolution and SNR of analog-to-digital conversions, and adopting a special sampling to suppress power line interference, as far as the noises are concerned.Key Words：solar energy water heater; scale; noise; oversampling; water temperature and level