Post by thread:[EE:] Noisy serial cable

At 10:22 AM 1/8/2004 -0800, John Pearson wrote: >I have found that the serial port cable, connected to my MPU board, is >creating some noise on my ADC readings. > >Any tips on reducing this noise? Probably, all you need to induce this noise is a cliplead between the two system grounds. If so, there's current flowing between the two systems. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Years ago, I was working on a telemetry system at a broadcast transmitter site. The equipment was in a rack beside the 5kW AM transmitter. The sample from the transmitter was ground referenced. I put a clip lead between the ground side of the sample and the rack cabinet the telemetry equipment was in. The clip lead melted.... Harold > Probably, all you need to induce this noise is a cliplead between the two > system grounds. > If so, there's current flowing between the two systems. > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > -- FCC Rules Online at http://www.hallikainen.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

At 10:59 AM 1/8/2004 -0800, Harold Hallikainen wrote: >Years ago, I was working on a telemetry system at a broadcast transmitter >site. The equipment was in a rack beside the 5kW AM transmitter. The >sample from the transmitter was ground referenced. I put a clip lead >between the ground side of the sample and the rack cabinet the telemetry >equipment was in. The clip lead melted.... I had a similar experience with shielded RS-485 in a grocery store. Plugged the cable into a concentrator, and the cable started getting hot. Turned out there was about 6V between the remote gnd and the local one. Lots of current available though. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

You should really consider measuring the voltage difference before correcting it... :-) My electronics teacher would, every so often, disconnect the cable from the TV in hte classroom and measure the ground to ground voltage and current. More than once he measured enough of a difference to put out a memo about teachers clipping off the ground terminal of extension cords, then plugging them in backwards so the neutral (which some TV sets would couple to chassis ground, and then couple to the cable system ground) was hot, and hot neutral. Cable company doesn't like it either... -Adam Harold Hallikainen wrote: {Quote hidden}>Years ago, I was working on a telemetry system at a broadcast transmitter >site. The equipment was in a rack beside the 5kW AM transmitter. The >sample from the transmitter was ground referenced. I put a clip lead >between the ground side of the sample and the rack cabinet the telemetry >equipment was in. The clip lead melted.... > >Harold > > > >>Probably, all you need to induce this noise is a cliplead between the two >>system grounds. >>If so, there's current flowing between the two systems. >> >>-- >>http://www.piclist.com hint: The list server can filter out subtopics >>(like ads or off topics) for you. See http://www.piclist.com/#topics >> >> >> > > >-- >FCC Rules Online at http://www.hallikainen.com > >-- >http://www.piclist.com hint: The list server can filter out subtopics >(like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.