Ground Loop Isolators - Cure Or Cover Up?

[timmo66]

I have read a lot on here about this subject and the general opinion is that they are just covering up a fault that might take a lot of work to rectify. While I do agree with this, and I am all for getting to the bottom of a fault and clearing it completely, I am in a situation where there isn't really a way around it.

 

We are fitting 21 cameras around a site that is pretty much split into two. DVR, monitor and half the cameras are all on one side of the side, the other half of the cameras on the other side of the site (all cameras powered locally). We have ran in cat5 cable with passive baluns at each camera, to passive balun racks in a patch cabinet with the DVR in etc.

 

All cameras on same side of site as DVR etc are all spot on. Cameras on the other side of the site are distorted at the DVR due to the differences in earths between the two buildings. Powering the distorted cameras from the same supply as the DVR wouldn't be practical due to the cable length required. Fitting ground loop isolators is the clear fix in my opinion, but perhaps a cover up?

 

Discuss.

 

[sjsturner]

I wouldent say cover up exactly. Other than cabling accross a mains supply your pretty fecked. Apparently some dvrs have a option to sync the grounding on bnc to help sort that out but cant say ive done it.

Only 1 cam per cat 5?

[Oxo]

You have an issue and two ways of dealing with it.

What is the most reliable and cost effective?

 

No brainer really.

[timmo66]

I wouldent say cover up exactly. Other than cabling accross a mains supply your pretty fecked. Apparently some dvrs have a option to sync the grounding on bnc to help sort that out but cant say ive done it.

Only 1 cam per cat 5?

 

We have more than one camera on the cat5, this has never caused me a problem before. I have viewed the images half way along the cable run via a test monitor and the pictures are perfect. Thought it might be a cable fault after that point so threw a temp cable to the DVR but still the same distorted picture.

 

You have an issue and two ways of dealing with it.

What is the most reliable and cost effective?

 

No brainer really.

 

I agree.

[sjsturner]

Sometimes decent psus can sort some of it out too. Easiest way is to power the other sides cams on batt i.e no earth and see if its sorted.

Would running the other side through a ups work too? Anyone tried this? Ups seperates out earth

[timmo66]

This is where I started to think. I tried two of the cameras that were distorted at the DVR on batteries, and still had the distortion. At this point I thought it was a cable issue, but we then powered up some of the other cameras on this side of the site and experienced the same picture quality. I thought the chances of having more than one cable fault were very slim.

 

I always had the earth inbalance in my head, but we basically tried EVERYTHING, and I mean EVERYTHING. I even sent an earth across on a spare cable to a screw on the patch cabinet.

[timmo66]

I'll maybe give you a view more details to chew on.

 

We picked on one particular camera in the end. A dome which was the closest camera on the other side of the site. The only way I could get the picture clear was to take that pair out of the balun rack, put the pair into a single balun on its own, and then run the coax through a hum eliminator (which I understand are slightly different to ground loop isolators).

 

If I run the pair through the balun rack (with all other cameras disconnected), and again through the hum eliminator, I still have the distortion.

[sixwheeledbeast]

Are you getting a ground loop hum and phase shift mixed up?

 

Cheap/Faulty Balun rack?

 

Cheap/switched mode PSU's?

 

Sounds like you need to diagnose the issue completely before you blame an earth loop.

 

Have you tested if a loop isolator actually works to fix the fault?

 

Try two cameras on batteries with standalone baluns, then try on mains and finally back in the rack.

[james.wilson]

6wb is dead on imo

[timmo66]

Are you getting a ground loop hum and phase shift mixed up?

Cheap/Faulty Balun rack?

Cheap/switched mode PSU's?

Sounds like you need to diagnose the issue completely before you blame an earth loop.

Have you tested if a loop isolator actually works to fix the fault?

Try two cameras on batteries with standalone baluns, then try on mains and finally back in the rack.

Sorry, but could you elaborate on your first point?

I have swapped the two balun racks around a few times, and still same issue. I thought the chances of two faulty racks would be slim.

We are powering the cameras with various power supplies at the camera locations, all of which are actually different makes and types. For example we have a 4 way 5amp power supply fitted at one corner of the building, we have two moulded power supplies inside a column at another corner, and a 24v AC power supply feeding the dome at another corner.

I haven't actually tried a loop isolator yet no. I have plugged a hum eliminator on but this only clears the fault on a camera when a single balun is fitted at the DVR instead of the balun rack.