中文摘要：

生化分析仪在对血液等样品进行分析的过程中,采样针表面的液体携带量经常会引起交叉污染,从而影响生化分析仪的检验精度.为了减少采样针的样品携带量,同时保证加样精度,提出了一种高可靠性的新型液面检测系统,系统将采样针作为电容式液面传感器,采用锁相环CD4046电路完成对电容式传感器电容变化的检测、信号滤波和控制信号的输出,实现了减少交叉污染、提高仪器性能的目标.临床检验数据表明：提出的液面检测系统具有稳定性好、可靠性高的特点.

英文摘要：

When using biochemical analyzer to analyze sample, such as blood, the liquid carrying capacity of the sampling needle surface will lead to carryover, which affect detection precision of biochemical analyzer. In order to reduce the sample carrying amount in the sample needle and assure precision of sampling, a highly reliable liquid level detection system is put forward. The system regard sampling needle as capacitive sensor of liquid level, using phase-locked loop circuit CD4046 to detecte change in capacitance of capacitive sensor, signal filtering and output of control signal, which achieve goals of reduction of cross-contamination and improvement of performance of instrument. Clinical detection datas show that the liquid level detection sysem has features of good stability and high reliability.