Just talk about the brands of online instruments I have seen. Besides what you mentioned, there are Kutcher, WTW, Shimadzu, DKK and Horiba.

The following are online monitors for chemical oxygen demand and ammonia nitrogen, which have been verified by National Environmental Monitoring Center, Guangzhou Wen Yi, Beijing Puxi General Instrument Factory and Shanghai Precision Instrument Factory. Here are some certified, Including Beijing Puxi General Instrument Co., Ltd., Guangzhou Wen Yi Technology Co., Ltd., Shandong Evergrande Environmental Protection Co., Ltd., Hebei Xianhe Technology Development Co., Ltd., Beijing Maoda Environmental Protection New Technology Co., Ltd., Bluestar Water Treatment Technology Co., Ltd. ... Beijing Huanke Environmental Protection Technology Company, Beijing Yuhuan Hongye Technology Development Co., Ltd., Beijing Zhonghuanfa Environmental Technology Group, Nanjing Linde Environmental Protection Instrument Co., Ltd., Jiangsu Luye Environmental Protection Technology Instrument Co., Ltd. Lanzhou Lianhua Environmental Protection Technology Co., Ltd., Hunan Zhicheng Technology Development Co., Ltd., Wuhan Taiken Environmental Protection Technology Development Co., Ltd., Hubei Intercontinental Environmental Protection Engineering Technology Co., Ltd., Hebei Yatai Environmental Protection Technology Development Co., Ltd., Sichuan Huitong Technology Industry Co., Ltd., Nanjing Huadu Environmental Protection Equipment Co., Ltd., Ltd., Shimadzu (Hong Kong) Co., Ltd., Shengli Oilfield Longfa Industry and Trade Co., Ltd., Shijiazhuang Gaode Environmental Technology Co., Ltd. Jiangsu Jiangfen Power Analysis Instrument Co., Ltd., Hunan Lihe Technology Development Co., Ltd., American HACH Company, Shanghai Precision Scientific Instrument Co., Ltd., Jiangsu Dongheng Group High-tech Industry Co., Ltd. (information given by previous bosses)