From: Massion, Gene Sent: Monday, September 12, 2005 2:21 PM To: 'abradley@whoi.edu'; fsonnichsen@whoi.edu Cc: Massion, Gene; Littlefield, Dick; Sullivan, Kevin; Raybould, Keith; slerner@whoi.edu; amaffei@whoi.edu Subject: RE: More on Noise/Ground issues with TD Al/Fritz Can we get the schematics for all the OBC boards in the node to help understand the grounding issues? Thanks Gene Massion Monterey Bay Aquarium Research Institute 7700 Sandholdt Road Moss Landing, California 95039 831 7751922 (tel) 831 7751646 (fax) -----Original Message----- From: abradley@whoi.edu [mailto:abradley@whoi.edu] Sent: Monday, September 12, 2005 2:21 PM To: fsonnichsen@whoi.edu Cc: magene@mbari.org; dick@mbari.org; ksull@mbari.org; keith@mbari.org; slerner@whoi.edu; amaffei@whoi.edu Subject: Re: More on Noise/Ground issues with TD All, The big capacitor on the TD board (the board with all the opto isolators) is across the main OBC 5v supply. This is sourced by switchers inside the OBC from the 48v. THE CAP'S LOW SIDE IS COMMON WITH ALL THE RS232 PORTS ON THE OBC! Grounding the cap is the same as grounding any of the RS232 ports on the OBC. Hope this helps... Al fsonnichsen@whoi.edu wrote: > > Gene came in this morning and we spent some time on the problem with > noise on the Timing Dist (TD) signal. After many tests is is very > clear that when we ground the filter capacitor on the TD board to > earth, the noise vanishes. We discovered this when we left an Ocscope accross the cap. > > Using a groundless plug on the 5V power supply driving the science > receiver didnt' alleviate the problem. > > Gene has obtained a 5V Vicor converter for the science receiver so > that it can run isolated. We will let you know. > > Meanwhile we are open to further suggestion. Al already has developed > a filter technique but I presume that we would want to solve this from > the ground perpective? > > Thanks > Fritz > > ---------------------------------------------------------------- > This message was sent using IMP, the Internet Messaging Program.