switchable or separate termination in can network

Hi All,

we  install fleet managenet devices in vehicles and sometimes connect its to
the CAN system too. We need to keep the termination value on 120ohm. The
device's installation manual offer to measure (with multimeter) the
resistance between the CANL and CANH wires (without powering the CAN
network; in general switch off the ignition). Depends on the measured value
we have to swith on or off the device's termination resistor.
My question: if the CAN network consists one or two node with switchable
termination resistor at the network's end, will the measurement (without
powering) shows the real network termination resistance? In case it won't
shows the real value, is there any easy way to determine it?  (or I have to
use scope to  evaluete the rise and drop edges?)

Thanks in advance: Tamas Hadarits
www.tachografszerviz.hu





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