Measure tide / swell

stuee · Sep 21, 2017

Hi,
I want to make something to measure swell and tides. Im messing with Raspberry pi 3 and have other sensors working but not sure how to do this one.

The tides mainly go from .0.3m to 4.5m and swell -2m > +2m

I was thinking of a floating sealed ball with an altimeter inside and also temp probe out the bottom a little.

After reading up how altimeters work is on pressure but if its inside a sealed ball would it not work properly, even when it gets warm and may increase the ball pressure a bit.

Am i thinking correct and if so what can it do or anything else i can try?

thanks for your help.

ericgibbs · Sep 21, 2017

hi,
Tides are usually measured with submerged pressure sensors connected to electronics using a cable with an air tube., swell can also be measured in the same way.

E
What is your location.

stuee · Sep 21, 2017

so you mean a ball for example, that has a long breather tube that also contains the cable too?

dr pepper · Sep 21, 2017

If you can get an accurate enough gps receiver you might be able to do it measuring altitude.

ericgibbs · Sep 21, 2017

hi,
The sensor is a thin metal diaphragm, one face is exposed to the sea water and the other face exposed to the surface air pressure by means of the air tube.
It is a differential sensor, which compensates for the ambient air pressure which effects the tide/water height.

The sensor sensor is suspended in the water at a depth below the lowest expected level.
In the UK we used sensors 1Bar upto 2.5Bar [ ~ 10mtrs to 25mtrs]

E

stuee · Sep 21, 2017

dr pepper said:
If you can get an accurate enough gps receiver you might be able to do it measuring altitude.

dr pepper, would it work ok inside a sealed ball? can i add external antennas?

Musicmanager · Sep 21, 2017

Hi

I've been playing with this recently, which you might find interesting in parts .. https://njhurst.com/electronics/watersensor/

S

atferrari · Sep 21, 2017

ericgibbs said:
hi,
The sensor is a thin metal diaphragm, one face is exposed to the sea water and the other face exposed to the surface air pressure by means of the air tube.
It is a differential sensor, which compensates for the ambient air pressure which effects the tide/water height.

The sensor sensor is suspended in the water at a depth below the lowest expected level.
In the UK we used sensors 1Bar upto 2.5Bar [ ~ 10mtrs to 25mtrs]

E

Hola Eric,

IIRC that was the system used in a vessel to get continuous draft readings even when underway.

How do you get the average value to catter for swell?

ericgibbs · Sep 21, 2017

hola,
For swell we used 3 axis Heave compensation onboard the Survey/Dredging vessel and applied correction to the water depth measured by the echo sounder in order to get a 'true' depth.

For a quay wall fixed tidal sensor we used tide height averaging .

In some underwater pipe laying projects we had to measure wave heights.

Eric

ericgibbs · Sep 21, 2017

Musicmanager said:
Hi

I've been playing with this recently, which you might find interesting in parts .. https://njhurst.com/electronics/watersensor/

S

hi,
One of the downside of capacitance and resistive sensors was the build up of algae and other crud on the face of the sensors.

A simple fixed height sensor can be made with a ultrasonic surface sounder located inside a stilling tube/well [ a bit of plastic drain pipe works OK].
Using a piece of pipe, a float/counter weight with a cord turning a potentiometer was used in the olden days
E

Musicmanager · Sep 21, 2017

Hi Eric .. .. .

ericgibbs said:
One of the downside of capacitance and resistive sensors was the build up of algae and other crud on the face of the sensors.

A simple fixed height sensor can be made with a ultrasonic surface sounder located inside a stilling tube/well

Yes, I've been reading about the issues and problems caused by build up of algae and the like. I've also read a bit about an ultrasonic solution. For my own purposes I'm actually looking for the means to assess the contents of a fairly modest tank that holds clean water, which is drained and replenished regularly.

I've had a play with capacitive probes with some fairly indifferent results so far, but I'm waiting on the arrival of some bits & pieces to make a more proficient probe. I've also got some ultrasonics on order, but there seems to be an issue with condensation moisture causing circuit failure. There is a solution but it is very expensive.

I wouldn't suggest that the article I appended will offer any solution, but it is a good place to start when discovering the pitfalls.

S

dr pepper · Sep 21, 2017

Yes so long as the plastic doesnt contain metal, some abs does.

Measure tide / swell

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