compass

Hi,
we want to use a deep-sea Aquadopp mounted to a the VA-steel frame of a bottom-water-sampler. The clamps are made of plastic, but the rest is steel. Do I have to be afraid of a deflection of the measurements of the internal compass by the steel frame?
Thanks,
Maik

Hi Maik,

I use a Vector, but I am sure that the setup is similar. I am able to run tests before I actually deploy so I can check things. The compass should not require to be submerged in the water to work. I would suggest running tests to verify that the compass is giving you headings that you believe in the lab. Then take it close to the frame and run the same tests to see if and if, how much the data changes. This should all be able to be done dry with the acoustic returns just being really noisy. That is what I would do with the vector.

This all changes of course if you have not already purchased the instrument, in that case, I would go and get an off the shelf compass and try the same test.

I do not know if steel when in the water will have different magnetic properties. I would not imagine so.

Hope this is a bit of help.

Dave

Hi Maik,

In the latest release of the firmware and software we have included hard iron calibration of the compass. This means that you can correct for magnetic sources that rotate in the same coordinate system as the compass itself. So even if your frame is magnetic, you will be able to remove the effect of the frame on the compass through calibration.  " />'>

To do the calibration you will need to perform a 360 degree rotation of the frame in the horizontal plane, while having an online connection to a PC that runs the calibration software.

Best regards,

Sven Nylund

Hi

I am not a materials expert but I believe there are several forms of steel - some are magnetic some are not.  In general, stainless steel is not - or very very weakly - magnetic.

- Atle Lohrmann