[TG] EV-1 Dilemma

[mprestero]

When I chose the location for my new EV-1 on my Alerion 26, I had two candidates - one on the forward side of the thin plywood bulkhead, with the battery combiner on the other side of that bulkhead, and the batteries and cables nearby; the other was five feet forward of that location, about a foot from the stem of the boat. I decided upon the location near the battery.

This past weekend I connected the EV-1 to the STNG network before I had the rest of the autopilot in place, and very quickly notices that the data out of the EV-1 didn't match reality. Now that I've read your post about heading sensors and magnetic interference, and recognize that I haven't done any linearization step with the sensor, it brings me to my question.

Except for when the engine is starting and running, there isn't much current in or out of the battery. The wonky heading info came with only the chart plotter, an iTC-5 and transducers, and an i70 running. That may be enough to make the series of almost random numbers out of the EV-1 appear. I chose the location because it is very near the center of the pitch and roll axes of the boat.

Should I move the EV-1 forward to the other more forward location awar from the batteries and battery cables even though it will see far more pitch motion?

Thanks.

Mark

[Tom - Raymarine - Moderator]

Hello Mark,

The EV sensor cores aren't affected by pitch and roll in the same way as the old fluxgate technology because they can measure magnetic field in all 3 axes, as opposed to a 2D fluxgate that only works when it's level and therefore needs to be gimballed. Being in a magnetically-stable environment is much more important than being central nowadays.

I'd suggest taking a smartphone with magnetometer app close to the location of the EV1 and measuring the magnetic field when the motors are starting/running and then stopped, and see what changes. If the effect is anything much (and particularly if the phone's heading reading deflects when engine is started/stopped) then you need to move the EV.

After moving the EV, if you do, I would do Compass Restart through the calibration menu in order to wipe old, irrelevent calibration data, and see how you go from there. If you're still not sure of the results, maybe post some video of the indicated heading data on the pilot display so we can see what's going on.

Regards,
Tom