This instrument is made in accordance to standards stipulated by American Society for Testing and Materials (ASTM) to develop Online Monitoring Corrosion Coupon, in which the coupon is made on the basis of China National Standard HG/T3523-1985 stipulated by Ministry of Chemical Industry. It can be used for online stimulation of the parameters such as flow speed and material in the field, and also for monitoring the equipment’s corrosion rate and surface corrosion in the circulating cooling water system. It also has significant meanings to make good use of water treatment chemicals in cooling water systems. Moreover, the Biological Silme Filter, which is made in accordance with China National Standard GB/T14643.1-93, can be installed at the end of this instrument, to measure the content of biological slime in the cooling water.