Per the NMEA 2000 standard, Instance numbers are pre programmed by the manufacturer and cannot be changed.

• A. True
• B. Cannot be changed
• C. Not specified
• D. False

Answer: (D)

Instance numbers identify a specific item of a given type on the NMEA 2000 bus, so you can have multiple identical sensors or devices without confusion. The standard allows these values to be configured by the user or adjusted by the device manufacturer through their configuration tools. A device may come with a sensible default instance, but nothing in the standard prevents you from changing it to reflect how the devices are actually arranged on the boat.

So, the statement that instance numbers are pre-programmed and cannot be changed is not correct. For example, you can assign one temperature sensor as instance 0 and another as instance 1 to tell them apart in your data.

The other ideas imply that these values are fixed or undefined by the standard, which isn’t the case. Instance numbers are meant to be configurable to accommodate multiple similar devices on the network.