National Instruments NI-9862 Getting Started page 13

Cabling Requirements for the NI-9862
Cable Specifications
Cables should meet the physical medium requirements specified in ISO 11898,
shown in the following table. Belden cable (3084A) meets all these requirements
and should be suitable for most applications.
Characteristic
Impedance
Length-related resistance
Specific line delay
Table 2. ISO 11898 Specifications for Characteristics of a CAN_H and CAN_L Pair of Wires
Termination Resistors
The termination resistors (Rt) should match the nominal impedance of the CAN
cable and therefore comply with the values in the following table. The onboard,
software-selectable termination has a nominal value of 120 Ω. If you are not using
the onboard termination, use the values listed in the following table.
Characteristic
Termination resistor, R
Table 3. Termination Resistor Specification
Cable Lengths
The cabling characteristics and desired bit transmission rates affect the allowable
cable length. You can find detailed cable length recommendations in the ISO 11898,
CiA DS 102, and DeviceNet specifications.
ISO 11898 specifies 40 m total cable length with a maximum stub length of 0.3 m for
a bit rate of 1 Mb/s. The ISO 11898 specification says that significantly longer cable
Value
100 Ω min,
t
120 Ω nominal,
130 Ω max
Value
95 Ω min,
120 Ω nominal,
140 Ω max
70 mΩ/m nominal
5 ns/m nominal
Condition
Minimum power dissipation: 220 mW
NI-9862 Getting Started
© National Instruments
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