Design of a high sensitivity liquid level detection（ LLD） system and its application in automatic biochemical analyzer is introduced. Contact capacitive method principles is regarded as core

a strong insulated metal double casing sampling needle is used as detection sensor

and a PLL phase comparator-based capacitance detection circuit combined with adaptive recognition algorithm of effective pulses is applied in the system

as a result

a performance indicators like cross-contamination rate is not more than 0. 3 % and as minimum sample is 2 μL

sampling error is not more than ± 3 % are achieved by the system. Automatic biochemical analyzer clinical application shows that the system has characteristics such as high detection sensitivity

reliability

operational stability

and so on.