Using longer (ribbon) cables for extended head cameras

Last Revision Date: 6/22/2015

Some users may wish to use cables that are longer than the original 6-inch ribbon cables supplied for our extended head cameras (e.g., extended head Dragonfly). This article describes possible problems and solutions for customers interested in using longer cables. The specifications of the ribbon cables currently being shipped with extended head cameras are as follows:

• • Pitch: 0.5mm
  • Pins: 20 pins
  • Length: 6 inches

We do not recommend using cables that are longer than the 6-inch (6") cables provided with our extended head cameras. Image noise generally increases as (among other reasons):

1. 1. Cable length increases;
   2. Multiple cables move closer together;
   3. Multiple cables move more parallel to each other; and/or
   4. Multiple extended camera heads move closer together.

Wehave not done any quantifiable noise testing with cables longer than the 6" ribbon cables provided with our extended head products. Therefore, we are unable to comment on results that may occur with longer cables.

The optimal cable length for our IEEE-1394 imaging devices is essentially zero. That is, the amount of noise is minimized in non-extended versions of our products. The maximum recommended length, given the physical properties of the Parlex ribbon cable and a need to balance cable length with acceptable image noise, is between four and six inches (4-6").

Some problems that may occur when the ribbon cable length is increased beyond 6" are:

• • It will behave more like an antenna, making it susceptible to cross-talk and EMC signals.
  • Timing will become an issue, since the CCD requires input from the camera as to when to capture an image. If the timing is shifted (that is, delayed or not at the most opportune moment) this will affect the Signal-to-Noise Ratio (SNR) of the resulting image.

For customers interested in using longer cables, the following suggestions may (or may not) help to minimize noise (NOTE: no quantifiable testing has been done using these suggestions):

• • wrap EMI (electromagnetic interference) shielding tape around the cable
  • use ferrites placed at the ends of the ribbon cables
  • attach ferrites to the ends of the 1394 cables that connect to the camera
  • keep the ribbon cables from multiple cameras as far apart as possible
  • if the heads need to be bolted in place to something, use plastic instead of metal
  • if multiple extended camera heads need to be attached to each other, separate them with a plastic barrier i.e. do not attach them using metal