How to select CoaXPress cables for machine vision and multi-camera systems

The continued adoption of CoaXPress in machine vision inspection and metrology systems is partially due to the higher video data rates enabled. But in multi-camera systems, the smaller more flexible cables are an advantage to fit in tight spaces and enable moving heads.

A multi DIN, BNC and single din connector, together with the micro BNC or HD BNC these are the CoaXPress connector types.

An overview of the possible CoaXPress connector types

For many CoaXPress imaging systems, the cable selection can be relatively simple. For others where a very long cable length is required, or there is a constantly moving imaging head (as common with multi-camera systems, such as with AOI), cable selection is more challenging.

So the first step with cable selection is to consider these 3 requirements:

The speed configuration
Cable length
Cable flexibility

Frame speed over cables

For details on the different frame speeds or bit rates over CoaXPress cables:

Several Versions of CoaXPress to Meet Different Machine Vision Requirements

Cable Length

The official CoaXPress compliance labels for CXP-12, CXP-6 and CXP-3.

One of the advantages of CoaXPress over other interface standards such as Camera Link and USB 3.0, longer cable lengths (i.e. 7 meters) can be used without repeaters which effect signal integrity. For most machine vision systems, longer lengths are not required.

CoaXPress certified cables can be verified by checking for the official compliance labels. The compliance label indicates the maximum interface speed for which the cable is certified.

Cable Flexibility

What is of more concern is the flexibility of the cables required. If the wrong cable is selected, there could be failures. One problem is that there is no standard definition of high flex cables.

The cable supplier can provide data/reference numbers on the following:

Flex test
Twisting test
U-shape bending test
Moved bending test
Cable bear bending test

If a highly durable, high flex cable is required, we recommend acquiring some samples and testing them under the system conditions. Within the CoaXPress protocol, there is a link test to check the data between the camera and frame grabber for errors. This is called the Bit Error Rate Testing and can help you verify the cable selection.

Contact us with any questions or for a free application note on using the Bit Error Rate Testing with the Euresys CoaXlink frame grabbers.