Fluxgate Compass large error

[marchhare]

I have an aging Raymarine set up and the compass reading on the ST7000 Control unit is now showing a huge error, about 90 deg out in Standby before I attempted to correct using the Control Unit. However this has now got an error of approximately 40 deg. Before I start making more adjustments has anyone had experience of a rogue Fluxgate compass. The autopilot will hold but is now a bit indifferent in operation. Interested in any theories or testing suggestions to correct or establish if it is a faulty unit.

 

[Cantata]

Have you gone through the calibration process (that involves going round in circles slowly)? I assume the instructions for yours will be similar to those for my ST4000.
Or it may simply be a poor connection. I've been caught out by connections on the back of my ST60s, where the cables and connectors look fine but caused erratic problems until I cut them off and crimped on new ones. The compass unit, fed by the fluxgate device, seemed especially vulnerable to this.

 

[Resolution]

Where is your fluxgate compass located? Anything metal been dumped alongside??

 

[FullCircle]

My fluxgate was affected by the cruising chute furling drum which I stored in aft cabin. About 40 degrees as it happens.

I had to calibrate mine about 3 times before it stabilised

 

[marchhare]

The compass has been in situ for 15 years and in the 8 years we have had the boat not issues at all.
I have yet to calibrate after the adjustments I made but not yet had the opportunity.
I will empty the aft cabin of the bikes but these have also been in there for a few years and check wiring.

 

[cliveshelton]

A simple tin of sardines did for mine. Fortunately I found it and moved it. All OK. The smallest metallic item within about 2 feet can do it.

 

[Boz]

I'm not sure you should be making 'adjustments'; as indicated in a previous post, the Autopilot is set intoCalibration mode and the boat motored in slow circles until the device tells you to stop?

 

[guernseyman]

I found it difficult to find a location well away from metal, but did the best I could.
After calibrating the compass display was well out. But it doesn't matter: I engage Auto mode, usually with the boat heading in the required direction, and the course is maintained, and can be altered. The fact that the control unit unit thinks it is heading 30 degrees away matters not: my GPS and ship's compass give me directional information.

Addendum

The manual says that there may be a large deviation on a metal boat. Ergo, I have a metal boat.

 

[lpdsn]

I have an aging Raymarine set up and the compass reading on the ST7000 Control unit is now showing a huge error, about 90 deg out in Standby before I attempted to correct using the Control Unit. However this has now got an error of approximately 40 deg. Before I start making more adjustments has anyone had experience of a rogue Fluxgate compass. The autopilot will hold but is now a bit indifferent in operation. Interested in any theories or testing suggestions to correct or establish if it is a faulty unit.

The older, more basic, fluxgate compasses can easily be knocked off their gimbles by mishandling. I had to send a new NASA one back after the Royal Mail did for it.

However, a metallic object nearby is the most likely cause. Best way to test is with a handbearing compass in the vicinity. Move it back and forth and it should be obvious if there's something big enough to cause 90 deg variation.

 

[charles_reed]

I found it difficult to find a location well away from metal, but did the best I could.
After calibrating the compass display was well out. But it doesn't matter: I engage Auto mode, usually with the boat heading in the required direction, and the course is maintained, and can be altered. The fact that the control unit unit thinks it is heading 30 degrees away matters not: my GPS and ship's compass give me directional information.

Addendum

The manual says that there may be a large deviation on a metal boat. Ergo, I have a metal boat.

If you do have a steel boat the reason is quite obvious - even if it didn't happen before the boat could have been remagnetised.
Typically such errors are caused by small peices of steel - in my instance it was the ring-pull on a beer can.

 

[Oldhairy]

Best way to test is with a handbearing compass in the vicinity. Move it back and forth and it should be obvious if there's something big enough to cause 90 deg variation.

:encouragement: If I had thought of that I would have saved myself a lot of work and worry.