An optical liquid particle counter system comprising: a liquid particle counter comprising: a flow chamber for flowing a liquid containing particles along a flow direction through a beam of electromagnetic radiation , an optical source , in optical communication with said flow chamber , for providing said beam of electromagnetic radiation ; a photodetector ; and an optical collection system for collecting and directing at least a portion of electromagnetic radiation onto the photodetector ; wherein said photodetector produces an electric signal characteristic of the number and/or size of said particles detected; a fluid monitoring system in fluid communication with said flow chamber for detecting bubbles in said liquid; and characterized in that the optical liquid particle counter comprises a processor in operational communication with said fluid monitoring system and said optical liquid particle counter , wherein said processor receives monitoring data from said fluid monitoring system and provides a control signal to said optical liquid particle counter or a component thereof resulting in a decrease of the power of said optical source upon detection of bubbles in said fluid or an increase of the power of the optical source upon a period wherein bubbles are not detected in said fluid, wherein said fluid monitoring system detects bubbles optically, electronically, acoustically, by pressure differential, by density, or a combination thereof and measures the size of said bubbles, and wherein said processor decreases said power of said optical source if a bubble has a diameter greater than or equal to the diameter of the particles being detected. a liquid particle counter comprising: a flow chamber for flowing a liquid containing particles along a flow direction through a beam of electromagnetic radiation , an optical source , in optical communication with said flow chamber , for providing said beam of electromagnetic radiation ; a photodetector ; and an optical collection system for collecting and directing at least a portion of electromagnetic radiation onto the photodetector ; a flow chamber for flowing a liquid containing particles along a flow direction through a beam of electromagnetic radiation , an optical source , in optical communication with said flow chamber , for providing said beam of electromagnetic radiation ; a photodetector ; and an optical collection system for collecting and directing at least a portion of electromagnetic radiation onto the photodetector ; wherein said photodetector produces an electric signal characteristic of the number and/or size of said particles detected; a fluid monitoring system in fluid communication with said flow chamber for detecting bubbles in said liquid; and characterized in that the optical liquid particle counter comprises a processor in operational communication with said fluid monitoring system and said optical liquid particle counter , wherein said processor receives monitoring data from said fluid monitoring system and provides a control signal to said optical liquid particle counter or a component thereof resulting in a decrease of the power of said optical source upon detection of bubbles in said fluid or an increase of the power of the optical source upon a period wherein bubbles are not detected in said fluid, wherein said fluid monitoring system detects bubbles optically, electronically, acoustically, by pressure differential, by density, or a combination thereof and measures the size of said bubbles, and wherein said processor decreases said power of said optical source if a bubble has a diameter greater than or equal to the diameter of the particles being detected. <EOS>