Re: Communications Cable

Cables are often a matter of compromises. Not only CAN has to be taken 
in account. Flexibility, temp. range, resistance to chemicals etc. has 
also to be taken into consideration. It is a matter of engineering. A 
mismatch in impedance will cause reflections wherever they occur and 
often the end points are not the worst spots. 100 ohm may work well if 
the rest of the network is done fairly well, the nodes have good 
oscillators  and the bit rate is not too high. Use an oscilloscope and 
check that the signal quality is good at the sampling point. If so, the 
solution will work well. Monitor the rate of error frames over time with 
a logger. If the rate is less than 1/10.000, it is probably good enough. 
CAN is very forgiving.
/Lars-Berno


On 14/07/04 20:26, John Dammeyer wrote:
>
> I've got a client who really doesn't like prefab cables or the larger 
> diameter Belden DeviceNet thin cable that is the proper 120 Ohms 
> impedance.They'd like to use this Alpha Cable which is rated at 100 
> Ohms +/- 10.Bit rates are 250kbps, total length of network isn't an 
> issue.Of course the hardware which has embedded termination is 
> terminated at 120 Ohms.
>
> http://www.mouser.com/ds/2/14/6459%20OR005-213474.pdf
>
> I'd like to be able to tell them not to use it but for a small network 
> with minimal noise producing peripherals I'm running out of arguments.
>
> Any suggestions?
>
> Thanks
>
> John Dammeyer
>
> "ELS! Nothing else works as well for your Lathe"
>
> Automation Artisans Inc.
>
> http://www.autoartisans.com/ELS/
>
> Ph. 1 250 544 4950
>