So one of the biggest things that sadly most people don't think about when it comes to cameras is how to power them... I have seen people that use the Power supply that comes with the DVR or NVR and use it with a PigTail or splitter whatever someone wants to call them and that isn't how it should be... Another issue is that people don't understand that most of the cables that comes with DVR's are really not a good Choice of cable for powering your cameras...
Most of you all are using cameras that are only 12vdc and this is ok for the most port but the people that like to try and push the distance of a Camera really needs to think about the power for the camera...
So if you have say small power cable for your cameras power it will have more resistance and this will cause Voltage Drop... You could have 12v power at the DVR end however at the camera end with not such great cable it could be as low as 9vdc and most cameras that was designed to run at 12vdc will not run at 9vdc.. Most cases camera and other devices have a +/- 10% loss and that means around 1.2v..
So then you have one of the PDU (Power Distribution Units) and some of them can be adjusted to give better power over distance. However then you have to worry about over powering cameras that don't have that drop... Like one of my PDU's can be adjusted to 15.5vdc and while that is great there are other factors that need to be addressed if your going to crank up the power.. That is going to cause Heat at the Power supply and could kill it faster then it would working at 12 or 13v... Also another issue is when your voltage drop ends because you moved the camera or that camera has been removed from the system now your OVER VOLTAGE PDU is going or could cook other cameras...
Another thing that people don't understand when it comes to cameras and power supplies it is good to have a good power unit for all cameras.. If you don't use a good supply you could end up with a Ground loop... A ground loop is when 2 or more cameras and or other devices are at different ground potential and the difference causes distortion on the picture. If the voltage measured between 2 cameras is more then a few volts that is a ground loop. This might show up on the ground side of the video cable... Then when the Video cables are connected to the recorder or monitor unit this could cause distortion and undesired picture... Because a Video signal is only 1volt peak to peak. So it don't take much in a ground potential for problems...
If you have a few cameras to many like I do and have multi power supplies you will want to make sure that you have your system set up with a Common ground between all your supplies to keep down the ground loop issue...
I have mentioned this on a different thread but another issue that can come about is when the camera uses a common ground for power and video.. I have one or maybe 2 of these type cameras running around. Sadly they are most times a lower cost camera... That could be a problem if ground loops are in your system...
I just thought I might touch base on things that could happen when you run multi camera system and have more then 1 supply... Maybe someone has this issue now and after reading this has some idea on what they can do to fix the issue...
One way to fix a ground loop is to get a Ground Loop Isolator Another way is as I said before make sure all the supplies cameras and recorders share the same common ground...
While some people with IP cameras think they are not going to be plagued with such an issue this isn't always the case.. If someone was to take apart their IP camera there is still 2 wires that are setup for VIDEO and the ground loop can still affect your video...
Also there is issue where people for IP cameras might be using Cables that are not really designed to be used with cameras anyway.. This could be because they are CCA cables and the cables in the casing are not even twisted right and this will be a common issue in that type of setup as well...
Little OFF topic but CCA don't USE for POE and don't use if you can get away with buying real copper cables.. If you push on a Cat cable and you can feel the wires inside moving around that isn't a good cable to be using for CCTV...