When termination resistors are connected at the wrong locations, the voltage drop in the power leads NET-S and NET-C will be:

When termination resistors are connected at the wrong locations, the voltage drop in the power leads NET-S and NET-C will be:

• A. Increased
• B. Decreased
• C. Unaffected
• D. Depends on installation

Answer: (C)

The essential idea is that termination resistors on a CAN/NMEA 2000 bus are for signal integrity, not for supplying or consuming DC power. The terminations are placed across the two data lines at the ends of the bus to match the cable impedance and minimize reflections during high-speed transitions. They do not form a DC path in the power or bias network that sets the idle voltages on NET-S and NET-C. In idle operation, both CAN lines sit at nearly the same bias voltage, so little or no current flows through the 120-ohm termination. That means the steady-state voltage drop along the data lines is governed mainly by the transceivers’ biasing and the wiring resistance, not by where the termination is located. If signaling occurs, the termination influences the shape and amplitude of the waveform (by affecting the impedance seen by the drivers), but it does not significantly change the steady DC voltage drop on NET-S and NET-C. So, the voltage drop on these data leads remains unchanged, even if the termination resistors are located differently.

The essential idea is that termination resistors on a CAN/NMEA 2000 bus are for signal integrity, not for supplying or consuming DC power. The terminations are placed across the two data lines at the ends of the bus to match the cable impedance and minimize reflections during high-speed transitions. They do not form a DC path in the power or bias network that sets the idle voltages on NET-S and NET-C.

In idle operation, both CAN lines sit at nearly the same bias voltage, so little or no current flows through the 120-ohm termination. That means the steady-state voltage drop along the data lines is governed mainly by the transceivers’ biasing and the wiring resistance, not by where the termination is located. If signaling occurs, the termination influences the shape and amplitude of the waveform (by affecting the impedance seen by the drivers), but it does not significantly change the steady DC voltage drop on NET-S and NET-C.

So, the voltage drop on these data leads remains unchanged, even if the termination resistors are located differently.