Jump to content
JohnBNC

Wanted detailed learning material about camera signal

Recommended Posts

Hi

 

Been doing cameras for years. I have an issue on a system.  Would like to see some detail about the signal that will help mel resolve the  issue. 
thanks

john

Share this post


Link to post
Share on other sites

1 hour ago, JohnBNC said:

Hi

 

Been doing cameras for years. I have an issue on a system.  Would like to see some detail about the signal that will help mel resolve the  issue. 
thanks

john

hi that would be a long discussion  with the many types of formats now available 

what type of system do you have and the problem

Share this post


Link to post
Share on other sites

Hi.  Thanks for coming back.  Is it hik Vision DVR, all cameras analog, coax. Mix of bodied, 240 V and newer two megapixel Hik, Daynite infrared turret cameras.  Just installed hikvision PTZ. Using overcoax communications no more than 100  -  150 m away. Mostly in duct, sone clipped direct internally to farm Building. picture is fine. Controls are fine until you oan up or pull out and get a lighting contrast between the sky and the ground - bright at the top dark lower down.  You get distortion lines at the top. if left a few seconds later you lose video signal. HIk said It was a camera and i put another one in, and it did exactly the same thing. I’m on site now doing some further checks and tests and confirming cable resistance, exact distance, whether it’s grounding out anywhere etc.  Will also get my monitor at the camera today. Try powering it from that 12 V supply supply et cetera .  Incidentally it works fine at night. Again leading me to think it is some form of internal overdrive issue with the camera itself (see link lower). Was just really after some up to date fault finding practices I can apply in addition  to  the obvious that I’ve stated above. Thanks

link to issue:

https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2F1drv.ms%2Fv%2Fs!AmkgTSceEZVbyVFHz-V1lQkNAcTs%3Fe%3DM4R9lH&data=05|01||f578ad4c3e174214af6d08dafd4e35b1|84df9e7fe9f640afb435aaaaaaaaaaaa|1|0|638100809610008724|Unknown|TWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D|3000|||&sdata=0IyXfnRjRmw6nFLvTRnsMHU2zHTq%2Fbw4%2BogEeCOPWKE%3D&reserved=0

 

Share this post


Link to post
Share on other sites

Hi

the Plug top PSU that came with the PTZ must be between 1 and 2 amp.  But…

Think i know what the issue Is.  On site now.  Plugging my LCD into the camera feed at the DVR end before the coax hum filters and it works fine. Connecting with my LCD after the filter I get the same issues with regards to loss of picture when it goes high light intensity levels.  I guess there is a negative interaction between the DVR, Camera and isolating transformer on the coax.  If i bypass the transformer and connect the cable from the camera directly to the DVR the camera does not come up at all. 

Did some snooping on the mains supply and some testing.

The Office with DVR is a metered TNCS, spliced under ground supply about 20yrds from the over head 11kv transformer.  The other cameras are fed from the same pole but further away from the 11kva transformer from a common supply but separate consumer units.  So will certainly be at different potentials. I was a bit naughty. I removed the earth to the DVR, connected the ptz direct to DVR and no issue. If i put back the isolating transformer, with the DVR still isolated from earth  i get the same issue.  If i leave earth to DVR connected and take out the filters, I am left with noise bars on most cameras, that move from the bottom upwards at varying degrees of speed I guess, depending on what is being used somewhere else on the dite or on other sites close to.

 

Options To fix:

1 - install a 25mm or larger managed earth between all  Consumer units to bring to same potential, then remove coax transformers.  Need to check IEE here. Would suggest supplementary earth stake at each incase PME fails..  could also do quick check with a 4mm just to make sure it works.

2 - check with manufacturer to see if the camera can be electrically isolated from local earth.  Need to test the theory on this by removing just this camera from the metal pole. And then remove transformer from coax and direct connect to DVR with all others still connected to transformers.

3 - check with HIK re DVR and options for electrically isolating the DVR from earth.  Unlikely as it is a metal Unit with a 230v supply. It will need an earth for the fault current, unless it can be converted to 12vdc only.

4 - some other kit that i can put between the DVR and the camera that isolates the earth  between but does no cause this signal issue i am seeing?

any thoughts?

thanks

 

john.

 

Share this post


Link to post
Share on other sites

John I would stop and have a think and a coffee 

first dvr is class 2 …… so no point looking at main earths total pointless and if overhead is it TT ? 

coax hum filter (humbugs) are not needed on analog HD they don’t work

There is a reason why I ask the power supply feeding the ptz and the size of it and it’s location 

 

Share this post


Link to post
Share on other sites

Dvr not double insulated, it is mains fed in a metal box, not 12 v separate.  As i say i removed earth connection from  Dvr via  the plug in the kettle lead, problem goes. But that is dangerous so not workable.  Coax line filters do work with ground earth issues on 240v cameras or cameras where the shield of the  coax is also electrically linked to ground. Any how thanks for the advice.  Taking the camera apart i see i need to remove the electrical connection between the two gas suppression  devices to earth. This will electrically remove the connection to ground.  I can then remove the filter. Yes puts DVR at increased risk of surge via local lightning strike, but no lightning protection on site so it is at risk anyway with or without this convection.  Not TT, TNCS. The overhead is 11kv transformer down to 420 / 230 TNCS.

Share this post


Link to post
Share on other sites
40 minutes ago, JohnBNC said:

But that is dangerous so not workable.  Coax line filters do work with ground earth issues on 240v cameras or cameras where the shield of the  coax is also electrically linked to ground.

I do hope your not in the UK 240v cameras ???

and no numbugs don’t work on HD cameras as digital signal not analog  (only analog)

why have you posted a video of your problem and come to a conclusion that it’s earth related even to the point your thinking of putting in 25mm earth bonding

you video shows a problem with a ptz that is class 2 so no earth and on top of that 

 

your picture if perfect until you move the ptz which also tells you IT IS NOT A EARTH PROBLEM otherwise it would always be there

 

you state in earlier post between 1 and 2amp psu for ptz 

yet you still have not given details asked …… size of power unit type and size of power cable and distance of cable 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×