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Figure 3. Connecting the NI-9881 to a CAN Device
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 Value
Impedance 95 Ω min,
120 Ω nominal,
140 Ω max
Length-related resistance 70 mΩ/m nominal
Specific line delay 5 ns/m nominal
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 Table 3.
Characteristic Value Condition
Termination resistor, R
t
100 Ω min, Minimum power dissipation: 220 mW
120 Ω nominal,
130 Ω max
Table 3. Termination Resistor Specification
© National Instruments
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NI-9881 Getting Started