搜索欧美日韩东南亚操逼视频,亚洲国产精品成人久久综合网,国产欧美一区二区三区在线老狼,人妻熟妇久久久久久精品无码,国产精品理论片在线观看,国产在线美女,国产精品一区二区制服,久久婷婷一区二区三区

At present, the plunger pump is the main infusion unit of liquid chromatography, especially the double plunger reciprocating pump. It has a well-designed eccentric cam, which is driven by synchronous motor or variable speed DC motor. The eccentric cam drives two pistons to move back and forth. At the same time, another piston corresponding to the long radius end of the eccentric cam is pushed in to open the upper one-way valve and send the mobile phase to the chromatographic column. The utility model has the advantages of convenient operation, stable flow rate, small pressure fluctuation and low failure rate.