Help on Noise Cancellation
Help on Noise Cancellation
(OP)
Hi All,
We have a coaxial copper cable used to communication and interlocks running parallel to a 13.8KV power cable at a distance of 1/2 ft in between them.
Problem our process engineers are telling is that they have a lot of noise and sometimes that trips the circuit.
My question for you guys is:
1. Would that power cable be able to induce significant noise inside that co axial cable? If it can then what is the minimum distance we should have in between them in order to get rid of the bad signals?
2. Is there a way i can shield the coaxial cable to be insulated from the inductance of the power cable.
Any suggestion on this matter would be appriciated.
I am not very familiar with communications so any literature to read about would also help me.
Thanks all
gokul
We have a coaxial copper cable used to communication and interlocks running parallel to a 13.8KV power cable at a distance of 1/2 ft in between them.
Problem our process engineers are telling is that they have a lot of noise and sometimes that trips the circuit.
My question for you guys is:
1. Would that power cable be able to induce significant noise inside that co axial cable? If it can then what is the minimum distance we should have in between them in order to get rid of the bad signals?
2. Is there a way i can shield the coaxial cable to be insulated from the inductance of the power cable.
Any suggestion on this matter would be appriciated.
I am not very familiar with communications so any literature to read about would also help me.
Thanks all
gokul





RE: Help on Noise Cancellation
Peter
RE: Help on Noise Cancellation
E.g. triple the length of the coax, and route it far away from the power cable, say around three sides of a rectangle, with the power cable being the fourth side.
Or add magnetic shielding to the coax, e.g. by running it inside steel conduit.
Or replace the coax with fiber.
Mike Halloran
Pembroke Pines, FL, USA
RE: Help on Noise Cancellation
It is a BELDEN 3092A RG-6/V Type Controlnet Cable. It is a Quad Shield 1C18 cable....
Is this cable good enough or is there any other suggestions????
Also Moving the cable to a distance might work, but its a overland conveyor and there is hardly room there to move it far apart.
Among the options replacing with fiber optics is the best, but i am not sure if we can do controlnet functions with fibre optics. Can WE?
Please advice
Thanks
gokul
RE: Help on Noise Cancellation
Can you run the coax through a conduit by itself? Conduit is great as it provides electric and magnetic shielding.
You can also try tri-axial cable. Use something like RG11 which provides 75 Ohm impedance between the inner shield and inner conductor (same impedance as your RG6) and ground the outer shield to the frame of the conveyor. However, if your problem arises from inductive coupling this will not help.
RE: Help on Noise Cancellation
Shielding only works if the entire system is designed to manage where the common mode noise currents are directed.
For example, if the RG6 was connected to an F-connector installed in a plastic box, so that the common mode noise on the shield had to flow into the box to complete its loop via ground, then the poor receiver circuit wouldn't have a chance.
This is just another consideration.
It might be a combination of several problems.
RE: Help on Noise Cancellation
I still highly recommend Kimmel & Gerke's book for EMC/EMI noise reduction:
http://www.emiguru.com/books.htm#EDN
It is comprised of 14 different articles that were published in EDN magazine in 1994.
John D
RE: Help on Noise Cancellation
Kudos....
gokul