Home
Projects
Line Frequency
The Voice of Protons
MCP3201 ADC -> RPI
Proton-Mag I
Proton-Mag II
Proton-Marine-Mag
UV PCB Writer
Lab Power Supply
Light Barrier
Strange Sensor
Solar Controller Hack
Pedal with 270℃ Poti
ABPM50
Misc Stuff
China!
About Myself
 
DE  EN

PPM - Marine/Underwater Version

This is an advanced hobby amateur project which includes the construction of a small submarine "towfish" that is towed to a boat. It allows to measure the magnetic field up to a depth of 100 meters. The basic idea is simple:


[Marine Magnetometer]

Here a closeup illustration of the "towfish". The sensor will be located in the left chamber, the electronics in the right. The Bluetooth junction-box resides in the boat. One requirement was that a cheap 3-pole cable shall be used with a length of up to several hundret meters.


[Marine Magnetometer]

The electronics part includes the sensor, the towfish electronics, and the junction box for the boat. The sensor is filled with about 300ml liquid paraffin which has the advantage that it does not freeze compared to water.


[Marine Magnetometer]

The electrical connections from the electronics up to the Bluetooth connection. We decided not to power the fish through the cable, adding a battery to the fish. This avoids the need of adding a DC/DC converter - that would produce electromagnetic disturbances - to the fish. Since there is no significant current through the cable, the communication protocol and levels can be simple and robust. All kinds of wrong connections will not destroy anything:


[Marine Magnetometer]

The app on Android can show either a numerical or a map screen:


[Marine Magnetometer]   [Marine Magnetometer]

The self-made boards for a prototype:


[Marine Magnetometer]

The manufactured boards (unfortunately not cheap for a hobby project):


[Marine Magnetometer]

A first test. It must be done outside of buildings:


[Marine Magnetometer]

Improvisong a climate chamber for simulating low temperatures:


[Marine Magnetometer]

The recording was done outside about 200m away from buildings with 1 measurement per second. The standard deviation is about 0.67nT. It would be very interesting to see such data from another proton magnetometer (Geometrics,...). Who can help? I would be happy if you would contact me!


[Marine Magnetometer]

Some hard work was needed to build the fish:


[Marine Magnetometer]

Finally it is ready, the part from the lathe above is the nose on the left in the following picture. The electronics and battery are in the left chamber, the sensor on the right, to avoid any influence:


[Marine Magnetometer]

After some pressure testing the first try in the sea (April 2023) was done!


[Marina Mag Real World Test]

A known sunken ship was detected perfectly. But this does not really show the performance of the magnetometer because the deviation was about 5000nT when floating over the ship. However this proves that the tuning-free electronics are valuable, typically a normal tuned PPM would have generated erratic values when being unsed in fields not being tuned to:


[Sunken Ship Magnetic Data]

Zooming in in some section of the recorded path, the low noise of about 2nT peak to peak can be observed:


[Noise Floor in Norway Sea]

So after all we are happy that we reached this point after so many hours of designing, building and testing. Let's see if we will find something nobody has discovered so far. ;)



2023 Alexander Mumm