PG-700 Heading is Off

[SeaBerry]

One of our clients is having an issue with his PG-700 heading being off by about 25-35°. He says it periodically flips from port and starboard. He has calibrated the PG-700 successfully with it showing all green lights, yet the heading is still off. He has a SCX-20 for primary heading but wants the PG-700 as a backup. Looking for some insight.

All the recently installed kit:
TZT-13X (2x)
DRS-6S NXT
HUB102,
SCX-20,
PG-700,
GP-330B,
FA-70,
Mercury Smartcraft-NMEA 2K Gateway,
IC-M605 (2x)
225T-TM904,

 

[TheReaper]

Is the heading consistently off by 25-35 degrees or does it matter which way you're going? Based on your pictures, I'd guess it's consistently off by that much. If you swipe from left-side of screen to right to bring out the data window...is the heading number displayed in the data box different than when you're using the SCX20 as the source?

My guess is that there's either an offset on the PG700 itself and/or need to go to Home-Settings-Initial Settings-Data Sensors-Sensor List and ensure that the PG700 has a device instance number of 1 and the SCX20 has a device instance number of 0. Also, in the Data Sensors menu, go to the PGN output selection and ensure that only Cross-track Error, Nav Data and Nav Route/Waypoint Info is turned on...everything else off.

 

[SeaBerry]

Is the heading consistently off by 25-35 degrees or does it matter which way you're going? Based on your pictures, I'd guess it's consistently off by that much. If you swipe from left-side of screen to right to bring out the data window...is the heading number displayed in the data box different than when you're using the SCX20 as the source?

My guess is that there's either an offset on the PG700 itself and/or need to go to Home-Settings-Initial Settings-Data Sensors-Sensor List and ensure that the PG700 has a device instance number of 1 and the SCX20 has a device instance number of 0. Also, in the Data Sensors menu, go to the PGN output selection and ensure that only Cross-track Error, Nav Data and Nav Route/Waypoint Info is turned on...everything else off.

The heading does seam to depend on which way you're going. It is consistently off within that range (slight difference between photo 1 and 2). I will double check variation between heading source, instancing and PGN output.

Thank you for your help.

 

[jp498]

For a backup, I'd leave the PG700 unplugged at the NMEA2000 bus with a label on it. Then it's safely out of the mix until needed; safe from surges, lightning, etc... Properly installed, the scx20 is very reliable and I expect it will be more reliable than previous sat compass choices because it's a simpler install. I have installed dozens and dozens of them with none being any trouble after install.

If you want backup, NMEA2000 is very much putting all your eggs in one basket. A design with backup might be two MFDs (ethernet interconnected), each connected to separate NMEA2000 networks on different breakers each with it's own SCX20. One would connect to the AP with NMEA2000 the other with a 0183 converter. I've done similar things; a boat had a SC50 that was starting to show it's age, and EVERYTHING was connected to it, because it has lots of outputs.... I added a SCX20 and NMEA2000 and some things are on one, and some things on the other. And nobody is going to panic if that SC50 does not turn on one day.

 

[SeaBerry]

Is the heading consistently off by 25-35 degrees or does it matter which way you're going? Based on your pictures, I'd guess it's consistently off by that much. If you swipe from left-side of screen to right to bring out the data window...is the heading number displayed in the data box different than when you're using the SCX20 as the source?

My guess is that there's either an offset on the PG700 itself and/or need to go to Home-Settings-Initial Settings-Data Sensors-Sensor List and ensure that the PG700 has a device instance number of 1 and the SCX20 has a device instance number of 0. Also, in the Data Sensors menu, go to the PGN output selection and ensure that only Cross-track Error, Nav Data and Nav Route/Waypoint Info is turned on...everything else off.

I have a spreadsheet attached of heading gathered from the PG-700 and actual heading. It seams to not be very consistent after all. Not sure if you have anymore insight. Thank you for your help

 

[TheReaper]

I have a spreadsheet attached of heading gathered from the PG-700 and actual heading. It seams to not be very consistent after all. Not sure if you have anymore insight. Thank you for your help

Based on your pdf, I would say that the PG700 has something pulling it off. I believe this because the amount of variation is something fixed (like off consistently by magnetic variation in your area) and that you mentioned your SCX20 works perfectly. It may be the mounting location of the PG700 or something metal or even electrical interference (i.e. power cable emissions) that is pulling it off.