Depth Sensor


#1

Greeting All,

Regarding the Depth Sensor, how I can understand in what depth my ROV is ?

And could you please tell me the location find the code related to Depth sensor in "Cloud 9".

Thanks,

Salman


#2

I see the depth overlaid on the camera view, in the numbers in the vertical bar to the right of the center of the image.

However, for me anyway, the numbers are not properly calibrated. I see it go from -.11 at the surface down to .05 under 2 feet of water (bathtub test). I suspect I have to do a calibration step, but I didn't see this in the guide; once I figure it out I'll update the guide.

You can also see it as the DEAP value in the set of numbers on the right of the page.


#3

Hi Mike:

Our experience at OpenROV has been that the depth sensors are remarkably accurate.

For the zero point of the sensor, there is a button on the page where you calibrate the motors (Diagnostics?) to zero out the depth sensor before you dive. This is generally only needed if you're in the mountains, so the depth sensor reads a noticeable negative number at the start of a dive, due to lower air pressure. We test regularly at Lake Tahoe which is at about 6000' of elevation, and the depth sensor reads something like -1 meter when you initialize the ROV.

If your ROV reads -0.11 when you wake it up, perhaps you live at slightly above sea level?

As for testing the scale factor of the depth sensor, make sure you realize that the sensing point is near the top of the ROV. If you put the ROV in two feet of water, the depth sensor is only submerged about a foot and a half.

Let us know if you continue to have any accuracy issues with the depth sensor.

-W


#4

Thank you Walt. I'm glad the depth sensor is accurate, and indeed under Diagnostics I was able to zero it. I'm a bit (~200 feet) above sea level here (Lexington, MA, USA).

I use a Google Chromebook to control the OpenROV, and I noticed the Diagnostics seems to be inaccessible on it: I can see the word Diagnostics, but I can't seem to scroll down and see the "zero depth sensor" button. When I use a normal (Macbook) laptop, I do see it and I am able to click it.

Next weekend we (me + 4 kids!) plan to take the OpenROV to our local pond for its first dive! I'll try to pay attention to how the depth sensor is behaving when we have much more water to work with.


#5

Hi,

Is there an issue with accuracy when diving in saltwater than fresh ?

jon


#6

Yes. Saltwater and Freshwater have different densities, so to get accurate depth information the ROV software needs to know what kind of water it's in.

The current depth sensor software is calibrated for fresh water. We've got most of the pieces in place to allow the user to switch between fresh and salt water; there are just some UI bits remaining, and we've been too busy with other stuff to finish that up. It would be a good project for somebody who knows javascript and wants to start playing with the OROV code.

-W


#7

Thank you guys.

Your guides have been really helpful ^_^ Now I can control the ROV through its Depth ^_^ my next step is to implement PID and make it Close-Loop.

I have a question, is it possible to interface with the Labview through the Arduino on the OpenRov ! is it applicable?

Also, the depth shown on the screen is in meter right ?

Looking for your advice,

Thanks,

Salman


#8

OK our first dive was mostly a success, and from that I do believe the depth sensor is accurate (once zero'd in the diagnostics page), and reporting in meters. Thanks!