How To Check Nmea Signal Using Multimeter

How do I check the health of my NMEA 2000 cabling earlier powering my network?

Maretron recommends using an N2KMeter to properly cheque NMEA 2000 network health when powered and devices are operational. The N2KMeter tin can as well provide a existent-fourth dimension detection of powered device advice issues such as excessive error frames, chip timing anomalies, device level bandwidth usage, and more. The N2KMeter is the official technician's banana to quickly locate NMEA 2000 network issues. This article's purpose is to cover the basic diagnosis using a Digital Voltage/Ohm Meter (DVOM) to systematically check all connections of your NMEA 2000 network are problem free.

The next steps will aid identify potential cabling issues before component damage can occur. You should always perform the following steps to ensure the cabling concerns are excluded before diagnosing detected anomalies on your operational NMEA 2000 network.

The pin assignments for NMEA 2000 Micro, Mid, and Mini size cabling is as follows:

Pin 1: Shield (Bare)

Pin two: NET_S (+12VDC, Red)

Pin 3: NET_C (Ground, Blackness)

Pivot iv: NET_H (CAN High, White)

Pin five: NET_L (Can Low, Blue)

First, visually cheque the following items on your NMEA 2000 network:

1) All connections are properly seated and secured in the NMEA 2000 network.

ii) The NMEA 2000 network has a fused link continued to the Ability Tap tee

3) (If you're using a Micro/Mid yellowish power tap, verify that the +12VDC connection is the brown and white wires, and the blue, gray, and black wires are all continued to DC- or your DC Ground).

4) Verify the NMEA 2000 network has two terminating 120Ω resistors continued on reverse ends of the entire network.

The next few steps volition require the use of a Digital Volt/Ohm Multi-Meter (DVOM).

Turn off the NMEA 2000 network power, remove the 2 terminating resistors (120Ω)

1) Proceed to measure each wire combinations (white/red, white/blue, blue/red, etc.) and verify that no shorted wires readings prove on the DVOM.

- When the 2 network termination resistors are removed, and the power tap is connected. The DC negative and the bare shield wire will show a resistive value on the DVOM. If y'all see any resistive values or cable shorts the cabling requires further diagnosis. Do not go along until the resistive short are removed from your cabling system.

Note: Technicians generally use Maretron's Field attachable connector (FA-CM-ST) to find wiring issues in NMEA 2000 systems, epitome shown in Effigy 1.

2) Adhere the termination resistors and connect the unpowered power tap to the NMEA 2000 network.

3) Plow on your systems DC power supply. Change the DVOM dial to VDC. Connect DVOM probes to pins two (Red wire) and 3 (Blackness wire) to ostend 12VDC shows. Move to various locations of your NMEA 2000 network to test that network power is consistently 12-13.five VDC.

4) Turn off the NMEA 2000 network. Remember to go along all devices disconnected. Now have a measurement for resistance turn your DVOM punch to Ω setting. Start to verify the following resistance measurements: 0Ω between pins 1 (Bare) and 3 (Blackness) of all NMEA 2000 drop connectors (This verifies that the shield is connected to ground). illustrated in Figure 2:

Annotation: The shield should be grounded at single location of the NMEA 2000 network.

v) Disconnect the power tap connectedness therefore splitting the network into 2 halves. Measure the resistance betwixt pins one (Bare) and three (Black) of a network connector. This measurement should be a very high resistance (OPEN). Reconnect the shield after this measurement is fabricated.

6) Reconnect the Power tap and adjacent mensurate virtually 60Ω between pins iv (White wire) and 5 (Blueish wire) of all drib connectors (This action verifies that both terminators properly to the NMEA 2000 network. If your measurement is 120 ohms, then only one terminator is continued. If you measure a very high resistance, and so no terminator is continued. The ii terminators continued measurement is shown in Figure 3:

NMEA 2000 Network Rules:

1) The two terminators are installed at contrary ends of the "trunk line" of the network.

2) Each node has a drop from the trunk of no more than than 6 meters

3) The sum of the length of all drops is less than 78 meters.

four) The maximum cumulative network length from device to device is as follows: 100m Micro/Mid, 250m Mini cable.

If you have gone through each of these steps free from issue, try adding components one by one to the NMEA 2000 network to bring communications on the network up slowly.

(Note: there must always be at to the lowest degree two components in a NMEA 2000 network (or whatsoever Tin can network) for data communication to have place.

Commodity Number: 443
Posted: Mon, Sep 12, 2011 seven:31 PM
Last Updated: Mon, Jul 6, 2020 5:14 PM

Online URL: https://www.maretron.com/support/knowledgebase/phpkbv7/article.php?id=443