Digital underwater length meter

[stevetto]

A digital underwater length meter is under construction for caveline measurement and polygon map construction.

Imgur

 

[wnissen]

Cool, is this based on sonar?

 

[Southside]

Cool, is this based on sonar?

It looks to me to be a line counter with digital readout.

The wheels pinch the line and there is a counter for the revolutions, revolutions*circumference=length of line let out.

 

[stevetto]

Yes, that is a simple counter.
There are magnets in one of the wheels.
The precision is around +-30mm at the moment. But I think it can be improved by changing the number and size of the magnets.

 

[stevetto]

20200707_064026 - Copy

• stevetto
• Jul 7, 2020
• 1

 

[D_Fresh]

Yes, that is a simple counter.
There are magnets in one of the wheels.
The precision is around +-30mm at the moment. But I think it can be improved by changing the number and size of the magnets.

+/- 30mm over what distance so far? Looks pretty promising! I'm assuming the margin of error is based on the magnet size... Would it be possible to mount the magnet(s) in the main housing with only a narrow metal piece in the wheel?

How's the buoyancy so far? Has it been checked or calculated?

 

[stevetto]

+/- 30mm over what distance so far? Looks pretty promising! I'm assuming the margin of error is based on the magnet size... Would it be possible to mount the magnet(s) in the main housing with only a narrow metal piece in the wheel?

How's the buoyancy so far? Has it been checked or calculated?

+/-30mm is calculated based on the distance between the magnets. At the moment there are 5 magnets in the wheel. There are 10 holes but if there were 10 magnets the hall sensor did not detected the magnetic field's change. Most probably the magnets are too strong or a different hall sensor would be necessary. With smaller and weaker magnets the accuracy might be improves.

Magnets has to be in the wheel, the hall ic needs electrical connection so it is easier to put it in the housing.

Bouyancy is negative most probably, but it will be checked in a cave this week.