Autohelm ST4000 adjustment

[mherrcat]

Capt Ron's thread on modern navigation got me thinking about this again.

Anyone have any enlightening thoughts on calibrating the Fluxgate compass in the ST4000? Mine shows readings about 30 degrees off from the GPS and steering compass. I have tried a couple of times to swing the compass according to the calibration procedures and every time I get an error display that says the boat is moving too fast; even at 2 knots!

I guess it doesn't really matter what the ST4000 compass reading is as long as it will hold a course; it's just annoying to see it off so far...

 

[treilley]

Are you sure that the FG compass is installed properly? It should not be near your engine or any other large metallic object. It should also not be near any electronics or magnets. I have min installed at the top of the bilges(just under the sole), 3 ft. in front of the engine and on the boat's centerline.

 

[Shadowfax]

I had trouble with mine also. You have to be going very slow and in flat water. Try 1 knot and maybe expand your circle.

 

[treilley]

Agreed. I just installed an S1 and we did go about 1 knot in a very protected harbor. We also did very large circles. Maybe 250 yard diameter.

 

[newpbs]

Proper Adjustment

I have just installed the S1. It also calls for a 2 knot circle, but that step did not correct the compass. I held a steady compass course, per the directions, and read what the autopilot had for a course. I then took the difference between the two headings and corrected the autopilot to match my compass.

Of course, the two autopilots are different and I'm not sure if this step is included in the ST4000. You might want to look over the directions again. I did find at least two errors in the directions, steps that were not included in order to get to set up items.

Good Luck

Paul

 

[mherrcat]

We also did very large circles. Maybe 250 yard diameter.

I was trying to turn as large a circle as possible in the harbor but it was probably not 250 yards in diameter. Harbor traffic was a problem, too.

It should not be near your engine or any other large metallic object. It should also not be near any electronics or magnets.

It is installed on the bulkhead at the aft end of the quarterberth, probably two feet starboard of the boat center line. The only electronics in the area is the main control unit for the autopilot which is maybe two feet away. (This is the maybe 6" x 8" box that all the wiring goes into, not the small control panel in the cockpit.) The batteries and systems breaker panel are at least five feet away.

I had trouble with mine also. You have to be going very slow and in flat water. Try 1 knot and maybe expand your circle.

Were you motoring or sailing? I don't know if I can sail that slow and even motoring at idle seems to get me at about 2.5 knots and is hard to maintain consistantly.

The water outside Channel Islands Harbor seems to rarely be "flat", but next time it is near that I guess I'll have to try expanding the circle. I just want to make sure the initial setup is correct; I know I'll have to input some correction to get it to jive with the steering compass.

 

[treilley]

Mark, is it really the aft end of the QB? That sounds like it is near the stern of the boat. I would move it forward near the fore/aft center and port/starboard center and keep it low.

Having the FG near the stern would definitely cause you troubles as it is a very sensitive instrument and could be affected by the up and down motion of the boat.

Are you sure you have an ST4000? The computer and control head on the ST4000 are all in one. I think don't they had a separate computer controller until the S1.

http://www.raymarine.com/SubmittedFiles/Handbooks/Legacy_Handbooks/Autopilot/ST4000Wheel.pdf

BTW, I just had all my navigation instruments properly turned. I had my Richie compass rebuilt and installed a new S1 AP. After turning the compass he adjusted the S1 so they would match. The S1 was off only a few degrees after doing the turns.

 

[Shadowfax]

Mark,

I was under power. You need to find a quiet cove somewhere. The slower the better the flatter the better. After you swing the compass you might have to set the variation.

Good Luck

 

[Loren Beach]

copied from prior message from Mark: "It is installed on the bulkhead at the aft end of the quarterberth, probably two feet starboard of the boat center line. The only electronics in the area is the main control unit for the autopilot which is maybe two feet away. (This is the maybe 6" x 8" box that all the wiring goes into, not the small control panel in the cockpit.) The batteries and systems breaker panel are at least five feet away."

If I read this correctly, the compass module was installed just about opposite of what the manual said to do.
OTOH, there was an older version of this unit with a control head that mounted on a clip in the cockpit and may not have used a separate compass module. Mine is an A4000S model, bought in late '94.
:nerd:
Putting it back in the stern means that even at a slower speed it is laterally displaced a lot during a turn compared to the center portion of the boat.

To assess the difficulty, one must consider that measuring the very small amount of magnetism of the earth is difficult for any sensor. The location of the sensor needs to be as near to the pitch and roll center of the boat as possible. In most boats there are practical reasons for not bolting it to the bottom of the cabin dining table (!) but you do want it near that area. This is where the boat moves the least and so gives the sensor a fighting change to read those invisible magnetic lines that textbooks are always talking about.

The next chore is to separate that sensor from local magnetic interference, and that can be from simple iron presence (tools, cans of food, utensils, any ferrous metal) and active local magnetic influences like pumps or fan motors. I try to keep it at least two feet away from these attractions and prefer three.

Sidebar: I pondered quite a while over where to mount our Autohelm sensor and how to run the wiring. Several possible locations were rejected due to wiring difficulties alone, and others due to obvious motors nearby. No problem since the install in '95, so the effort seems to have paid off.

Good luck on resolving this. The AP is an absolute necessity on most of our boats.

Best of luck,

Loren

ps: here is a current Raymarine link for the 4000 series, and if that's what you have, all of our compass sensor advice is worthless.
http://www.raymarine.com/SubmittedFiles/Handbooks/Legacy_Handbooks/Autopilot/AH4000.pdf

 

[mherrcat]

Ooops. Sorry to get everyone confused. It turns out the unit is probably the S1 Wheelpilot. (The boat is about 150 miles away, I didn't have the manual here at home and I haven't looked at it for a while. My bad...)

I did look at the list of manuals on the Raymarine site including the Fluxgate Compass installation guide. The location of my compass is not ideal, but it is acceptable according to the guide. I think I should try to relocate it. Possibly to inside the access area for the speed/depth transducers in the V-berth; that's the only accessible place I can think of that will be low and on the centerline of the boat. Or maybe in the port setee locker just next to the center aisle, but that area gets a lot of stuff stored in it, including metalic objects and would put it within about six or seven inches of keel bolts.

More dilemmas, including do I have enough cable...

Again, sorry for the confusion.

 

[Shadowfax]

I don't know about mounting it near the transducers. The depth is sending out pulses and most speed sensors work with magnets, at least mine do.

Loren is right on with his observations, but the both of us though you had a Autohelm 4000, so your unit may want different conditions to swing the compass, but the conditions I noted before for swinging the compass can't be far off no matter what unit you have