kensplace 0 Posted December 5, 2006 Earthing should be easy, you earth something for protection.. But in cctv its a different matter, in fact its positively confusing....... Should you earth the multiplexer if it has a earth tab? Should you earth the coax? Should you earth the baluns? Thing is, if the plexer has a earth nut, why do many sites say DO NOT earth cameras as this will cause them to be a magnet for lightning strikes and offer less surge protection? If a camera is supposed to 'float' then there is no problem when the cam is connected to all double insulated equipment... BUT what about when the camera is connected via a capture card, such as a tv card, or a geovision card? Those cards are EARTHED to mains earth (as far as I know), as they come into contact with the pc case, which is mains earthed - thefore the cams are no longer floating. Is this safe..... It may work, not bothered about that, what Im wondering, is: Is it safe...... Im lost on this issue, cant get my head around it. Then there are ups issues, a ups will supply mains even if its earth fails... So previously earthed equipment will run at full mains with no earth..... Reading up on it just confuses the issue, with lots of conflicting advice. Share this post Link to post Share on other sites
rory 0 Posted December 5, 2006 just dont short it out and it will all be good .. Share this post Link to post Share on other sites
kensplace 0 Posted December 5, 2006 Not sure what you mean... Share this post Link to post Share on other sites
jisaac 0 Posted December 5, 2006 your cams are suppose to be grounded at your head end. If you double ground it then you will be very prone to lighting strikes as the camera will be the path of the current overflow. Cameras should not float. They will be grounded at your head end and any other ground will also give you a ground loop. Share this post Link to post Share on other sites
Cooperman 0 Posted December 8, 2006 kensplace, The general rule here in the U.K. is that you pretty much have to ground everything, with only a few exceptions. If for example you install a metal cased weatherproof housing with a built in heater 24v+ AC, then you will need to ground the housing. If the camera is 24v+ AC then you will need to ground that as well; if the camera is 12v DC, then as long as it is isolated from the housing, you won't need to ground it, and there is minimal risk of any earth loop being induced. Any mains powered (240v AC) equipment must be earthed, unless it is a double insulated unit (for example a plastic cased CRT monitor)., in which case the mains lead will probably be a 2 wire figure 8 type plug / socket arrangement. You can generally spot a potential (pun not intended ) earth loop situation, by looking at the length of the cable runs, and seeing if the local mains connections are fed from different distribution boards. If there is a risk of earth loop, and the equipment cannot be commoned to a specific earth point, then you will have to consider using isolating transformers to prevent the problem occuring. Despite occasional freak weather over here, lightning strikes causing camera failure are actually quite rare. Share this post Link to post Share on other sites
VST_Man 1 Posted December 9, 2006 I think there are 2 seperate issues here, both have a seperate meaning. Grounding equipment has been around for a while and it is pretty much a no brainer. Grounding provides a path of least resistance. Light'n will follow the path of least resistance........hence the resoning to ground. Ground Loop is caused from differences in potiential. All objects hold a "charge" You. me, buildings, wire, power...all hold a "charge/potiential". When you attach a camera to an object with a potiential and connect that camera via cable to another object with a different potiential, it causes the potientials to move from lower to highest, or negative to positive. This movement imposes a signal onto the cable that interferes with the original cctv signal causing it to distort. Ground loop isolators block the potiential movements and allows the cctv signal to pass clean. the higher/larger the potiential the harder it is to block. My point is, grounding and ground loop are two seperate things and should not be confused as one. both are required/present. I've seen GL caused by mounting camera's on telephone poles that carry high voltage power and also when a camera mounting screw penetrates a electrical wire/sheild. Both created GL I'm not an expert, just learned this while communicating/reparing in the USMC...and also on the job here. Share this post Link to post Share on other sites
Cooperman 0 Posted December 23, 2006 Grounding provides a path of least resistance. Light'n will follow the path of least resistance........hence the resoning to ground. Ground Loop is caused from differences in potiential. My point is, grounding and ground loop are two seperate things and should not be confused as one. both are required/present. Absolutely spot on VST! The only slightly embarassing thing is, two weeks after I posted about lightning strikes knocking out cameras here in the U.K. being a very rare occurence, what happens ..? A few days ago I had a camera sent back for repair, a nice 12v DC powered B/W Sanyo model, fried to a crisp by a lightning bolt! You just can't make these things up Share this post Link to post Share on other sites
rory 0 Posted December 23, 2006 LOL .. coop where yah been .. Yeah Ive yet to see a camera here hit by lightning . .. our biggest problem is low voltage spikes, brownouts, blackouts, hums, etc. Share this post Link to post Share on other sites
Cooperman 0 Posted December 31, 2006 LOL .. coop where yah been .. Yeah Ive yet to see a camera here hit by lightning . .. our biggest problem is low voltage spikes, brownouts, blackouts, hums, etc. Hiding rory ... what do you think ... Way too much work to deal with at the moment, so sadly not much time on here these days Just to add insult to injury, I can now add a recorder to the list of recently zapped equipment. Global warming and wacky weather; another few years and we'll probably be looking at using underwater cameras Share this post Link to post Share on other sites
rory 0 Posted December 31, 2006 LOL .. yeah man, but here its hot and dry .. actually its very warm for this time of the year .. ive been running the AC all day .. I hope we get some kind of winter this year .. so far there were a couple days in November or something like that, when it went down to 60 .. but that was it .. basically its like 80 now. Share this post Link to post Share on other sites
Cooperman 0 Posted December 31, 2006 LOL .. yeah man, but here its hot and dry .. actually its very warm for this time of the year .. ive been running the AC all day .. I hope we get some kind of winter this year .. so far there were a couple days in November or something like that, when it went down to 60 .. but that was it .. basically its like 80 now. Slightly off topic , but it's the same problem right across Europe. Here in London, we've got trees starting to bud, which don't normally start before March, and right across the main ski resorts in central Europe, they're reporting that they don't have any snow We've had bucket loads of rain over the last few weeks, and currently have a hosepipe ban due to a "drought". Water water everywhere, but not a drop to drink So rory, if you've been running the aircon all day, no wonder we have global warming Share this post Link to post Share on other sites
