Measuring NMEA output

R

rascacio

Well-Known Member
Joined
24 Jan 2009
Messages
111
Location
UK at present
Visit site
I have a VDO Logic wind speed mast head and display unit that came with the boat, however I do not know if it is putting out any NMEA info even though it should.

Does anyone know how to measure if there is any output ?

It appears to be connected to the pilot/plotter system but neither show any wind direction or speed info.

It works perfectly as a wind speed direction unit but I would like to have it linked into the autopilot/plotter system.

Any ideas ?
 
If you have a PC with a terminal emulator programme, such as Windows HyperTerminal, (free download) and a serial connection, direct or via USB, it is possible to view the transmitted NMEA183 sentences.
 
From what I can remember it is a 5v pulse every one or two seconds. You can see it with a volt meter across the pair of wires. There is also a way to read the string with a laptop using an emulator program but I'd need to google that
 
Spyro said:
From what I can remember it is a 5v pulse every one or two seconds...
Click to expand...

The level can vary up to 12V, depending on the manufacturer. The pulses may also be fairly continuous, but should register as a fluctuating voltage on a meter. Once this has been checked, the next stage is to try with a terminal emulator.
 
Last edited:
rascacio said:
I have a VDO Logic wind speed mast head and display unit that came with the boat, however I do not know if it is putting out any NMEA info even though it should.

Does anyone know how to measure if there is any output ?

It appears to be connected to the pilot/plotter system but neither show any wind direction or speed info.

It works perfectly as a wind speed direction unit but I would like to have it linked into the autopilot/plotter system.

Any ideas ?
Click to expand...

Does the plotter have a setup menu where you can choose the data it displays? My Navman 5600 only displays what you select, not every nmea sentence it receives.
Ian
 
ianj99 said:
Does the plotter have a setup menu where you can choose the data it displays? My Navman 5600 only displays what you select, not every nmea sentence it receives.
Ian
Click to expand...

Hmm not sure. I'll check it out when I'm at the boat again.

Thanks for that and thanks to everyone else who's replied
 
Your best bet is to use Hyperterminal (for some reason it is not part of Win7 but you can download and install it OK) You will need a laptop with a serial port or a USB-serial adapter. The output is likely to be either 4800 or 9600 baud, N,8,1 and you should see the messages. A typical message set would be $GPGGA (position) $GPVTG (speed) and maybe some others. If you see 'junk' instead of these proper messages then it is likely you have the baud rate incorrect, just experiment until you see something sensible.

If this is too difficult you could do a very coarse test using a multimeter. Set the meter to 20V DC or something similar. Put the ground (black) on pin 5 and the red probe on pin 3. You should see a brief fluctuation every second or so. Depending on your multimeter you may or may not see a voltage of around 12V. Another way would be to use a 12V LED across the same pins and watch for a flicker at once per second or so.

Hope this helps, feel free to PM if you need some more help

cheers

rich
 
You must log in or register to reply here.

Share this page

Top