I've got a twisted pair cable that I'd like to use for connecting distributed systems that use 1Mbps CAN network. The problem is that I don't have a clue what's the impedance of this cable and I know that these systems have 150ohm terminating resistors. How can I evaluate the cable impedance to verify if it matches this network?
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Do some time domain reflectometry, a useful video to this process is probably one from w2aew. He shows it with a coax, but it should work with anything that has a somewhat consistent impedance.
Is this for a one-off project or for "real-production" use?
For one-offs, which aren't pushing the limits (eg of bus length) it'll probably work fine. CAN is very tolerant of all sorts of reductions in signal quality, and even 1Mbps is not really in "transmission line" territory. As long as you have the terminators at the end of the bus it'll probably work.