中文摘要：

现代测量技术尤其是现代环境监测要检测或监测的物质成分往往都是含量很低的，特别是在痕量成分的分析检测中，在极高的背景噪声中提取很弱的分析信号，一般需采用的锁相技术，必须用斩波控制电路提供稳定的参考频率。所以要确保斩波控制电路能够输出稳定高精度的基准频率，这样才能准确地分析测量。

英文摘要：

For modern measurement technology, particularly, modern environment monitoring, detected or monitored content tends to be very low in material composition. Especially, in trace content analysis and detection, analysis signal is very weak and would be picked up against strong background noise. Usually, phase lock - in technique is adopted, and chop control circuit should be used to provide a stable reference freguency signal. For accurate analysis and measurement, chop control circuit must output stable and high accuracy baseline frequency signal.