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Depth Sensor

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New Member

I have a submarine that can submerged as deep as 5 meters. In this project, I need to find the vertical position of the submarine as it dives down the water vertically (Need only the current position ).

The submarine waterproof casing is big enough to put in a sensor inside, unless the sensor is waterproof as well.

A few enquiries
1. Is the a very simple depth sensor that i can create? if no, then
1. What sensors do i need that can easily integrate with a PIC? and
2. Can i get it to send data wirelessly?

Hope to hear from you guys soon!..thanks


Umm, an electret microphone might work, not sure what the DC offset voltage change is going to be but if you just use hotglue to encapsulate it you should get a water proof pressure trasnducer, no idea what range it would be good for though.


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Water depth is usually measured by pressure.
The pressure at 5metres is about 0.5 bar.
Small pressure transducers are available, but can be expensive.


On edit, provoked by a PM from Eric Gibbs (thank you), the pressure at 5 metres is 0.5 bar, not 0.5 millibar as I had previously stated.

As a quick rule of thumb, to find the water pressure in bar, divide the depth in metres by 10.

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Well-Known Member
Most Helpful Member
hi shammm,

How big is this submarine.?

For all your conversions the attached zip file should help.:)



Well-Known Member
For the sensor part, you can use a MAP -manifold air pressure- sensor out of any late automobile wreck yard; it is about 1 square inch, located attached to the intake manifold. A tiny balloon tied to its port will make it work as depth sensor.
Takes 3 wires- +5V; Gnd; and output signal.

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To send data wireless, a piezoelectric transducer salvaged from a beeper or telephone electronic ringer can be driven by your PIC; and received by another.




In static conditions, each foot of water depth will contribute 0.43 psi to the sensor output.

At a depth of 5 m or 16.4 ft, you would then have a total sensor reading of 7.05 psi.
Probably select a pressure sensor of from 0 to 15 psi gage ... not absolute.

Any dynamic or motion effects of the vessel would alter the sensor output.
Maybe you could devise some sort of L-shaped tube sensor, facing to the stern, so that forward motion would not cause an excessively high, and incorrect, depth reading.

A lot of sensors have a linear voltage output. There are also commercially produced 'readout' interfaces.
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New Member
Check out the Motorola/Freescale pressure sensors.

The MPX series (0-10KPa, 0-50KPa, 0-100KPa and 0-500KPa) have a direct voltage output varying between types from 2.5 to 9mV per KPa.

For your application a 100KPa sensor (MPX21000DP) would be best suitable (100KPa=1,000mb=1bar) You could also use the 0-50KPa type (MPX2050DP) but getting close to overrange when at 5m (0.5bar pressure) water depth.

Using a single pressure port sensor the pressure sensed is the difference between standard atmoshpere value (1013.2mb/1013.2HPa/29.92inchHg) and water depth.

On the other hand you won't need any pressure measurement and indicate the true depth by the lenght of the remote antenna cable with the antenna attached to a floating "island" just by using a reel and a rotary encoder to count the steps to be converted to depth readout.

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