为实现全自动凝血分析仪加样过程高灵敏度和高精度的液位检测，采用了电容传感器原理和步进电机运动控制相结合的方法。介绍了探针式电容传感器的结构与工作原理；分析了电容/周期转换法的检测原理；组建了实验系统对灵敏度和测量精度进行检测。实验结果表明：加样针接触液面的瞬间，脉冲周期发生40%左右的显著变化，液位测量的标准差为4.1μm。%To achieve high sensitivity and high precision liquid level detection on pipetting process of automatic coagulation analyzer,a capacitive sensor principle combined with stepper motor motion control method is used. Structure and working principle of probe-type capacitive sensor are introduced;detecting principle of C/T conversion method is analyzed;an experiment system is set up to test sensitivity and precision. Results show that the change of pulse period reach to around 40% at the moment while pipette is contacting liquid surface,the standard deviation is 4. 1μm.
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