Genesis Magnetization

[Rick Brant]

I've been having some compass issues recently. My console compass started giving strange, variable, mostly wrong readings during a dive (no DPV), and when it did the same thing on a second dive I replaced it with a new compass. That one had the same problem so I started looking a little more closely at what was going on. It looks like my console -- which has depth and pressure gauges -- is slightly magnetized. I also have a retractor on the console and that is magnetized as well, more than the console itself it seems. Putting a compass into the console gives wild results because there is a baseline magnetism plus a variable component as the retractor moves around.

All this started after a long DPV excursion using a Genesis 3.1. It appears that the console may have gotten magnetized either during that dive or maybe during post-dive transport. The latter seems more likely as it is possible that the prop assembly on the DPV was close to the console in my car. The only reason I think it might have happened during the DPV dive is I did have some minor compass issues then as well. Nothing as dramatic as what I am seeing now, but it was definitely giving some bad readings.

Is anyone else seeing compass issues with the Genesis? I want to figure out a system I can rely on while using the DPV but more importantly I want to avoid ruining a console for future compass use. I don't think there is a way to reverse this so I can't really use the console with a compass.

 

[Rick Brant]

I should mention, my console is clipped off to my crotch strap d-ring when diving. Not that close to the DPV but definitely closer to the prop than the front.

 

[Jon Nellis]

It is most likely the clock spring in your retractor that has become magnetized. If you removed the prop (say when rinsing) and held it next to the retractor, that could magnetize it. But when installed, the magnetic coupling's magnetic fields are closed loops and don't extend beyond the housing.

The change between retracted and extended positions is due to the change in shape of the spring between the two states. If you have a demagnetizer, run your retractor over it.

 

[missionmtb]

https://a.co/d/fxCKblK

Grab a magnetic field visualizing sheet off amazon and look for your field Also, read up on halbach arrays to get an idea of what John is talking about. The motor is probably a different arrangement but same idea as far as field shape.

Halbach array - Wikipedia

en.wikipedia.org

Fun fact, this is how they make fridge magnets so strong at close distances. Rubber can hold 90 wt% additives, in this case FeC.

 

[Rick Brant]

I think the console itself is lightly magnetized. I see a major issue when the retractor is nearby but also see errors when the retractor is removed. Just putting the compass near the console (no retractor) moves the needle.

 

[Jon Nellis]

"Console" is an ambiguous term. What is your "console" and what else is on it? If you have a computer or something else that requires a battery, the cell is likely the next major contributor. How much deflection is occurring?

 

[Rick Brant]

See my first post -- just a depth and pressure gauge. Standard Aqualung with a compass in the rear slot. Computer is on my wrist.

It's much less deflection with just the console. I won't be able to get exact values for a few days. It's more than I would be willing to live with in any case.