A liquid level detecting system applied in the completely automatic biochemical analyzer is introduced. This system uses double-layer needle-plate capacitor as the liquid level detecting probe. Detecting signal generated by double-layer needle go to hysteresis voltage comparator to form square wave. The square wave is used as the pulse source of the single-chip counter. The master controller is LPC916. In the program, through comparing the differential value of pulse number with fiducial value in the same time to judge whether the probe head contacting the liquid level or not. The system eliminates the effect of external interference signal on the measuring result by using the capacitance matching in the hardware and the self-adaptive algorithm in the software. This system has already applied in the completely automatic biochemical analyzer. The experimental result is correct, which proves the usefulness and stability of this detecting system.%介绍一种应用于全自动生化分析仪上的液面检测系统.该系统采用双层针—平板电容器作为液面检测探头,其产生的检测信号经滞回电压比较器形成方波,产生的方波作为单片机计数器的脉冲源,系统使用LPC916为主控芯片.在程序中,通过把相同时间内脉冲个数的差值与基准值进行比较,来判断探头是否接触到液面.在硬件上采用了电容匹配,在软件上采取了自适应算法来共同消除外界干扰信号对测量结果的影响.本系统已经应用于全自动生化分析仪上,经过实验,检测结果准确,从而证明了该检测系统的实用性和稳定性.
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