Homebuilt ROVs Forum

Ok, I have been unable to find any sound data on what does and doesn't work for depth sensors. I would like to find a definitive answer. Ideally a few pictures and schematics to support. I am trying to avoid the fish finder method, as this is not as easy to integrate with an Arduino (unless I missed something). I prefer the build-it-yourself approach.

I have found a great range of product, but I am unclear on how exactly something like these sensors would need to be installed?
http://sensing.honeywell.com/index.php/ ... /1/re_id/0


As I gather, there are 3 types of pressure sensors.

Absolute: no reference required
Differential: reference required
gage: referenced to atmospheric pressure

From what I have learned so far, an ROV would likely require an Absolute or a gage sensor.

If I understand correctly, the gage version would have to be calibrated before each dive. The sensor would be initialized at the surface to get your base line reading, then, as the ROV descends, the output will increase proportionally based on the depth as detected by the rise in the internal pressure of the ROV as it descends.

The absolute has its own internal reference to compare against, and there for would not require an initialization. In this case however, if you are not diving at sea level, you will get a false reading on depth, unless you compensate for altitude.

The Differential would require a connection to the surface to compare to the pressure at depth, and return a value that is in relation to the difference detected between the two.

Does anyone have any background in this? Am I on the right track? Can anyone provide more specific information?

Thanks,
"KR2_Diving"

KR2_Diving wrote:Ok, I have been unable to find any sound data on what does and doesn't work for depth sensors. I would like to find a definitive answer. Ideally a few pictures and schematics to support. I am trying to avoid the fish finder method, as this is not as easy to integrate with an Arduino (unless I missed something). I prefer the build-it-yourself approach.

I have found a great range of product, but I am unclear on how exactly something like these sensors would need to be installed?
http://sensing.honeywell.com/index.php/ ... /1/re_id/0


As I gather, there are 3 types of pressure sensors.

Absolute: no reference required
Differential: reference required
gage: referenced to atmospheric pressure

From what I have learned so far, an ROV would likely require an Absolute or a gage sensor.

If I understand correctly, the gage version would have to be calibrated before each dive. The sensor would be initialized at the surface to get your base line reading, then, as the ROV descends, the output will increase proportionally based on the depth as detected by the rise in the internal pressure of the ROV as it descends.

The absolute has its own internal reference to compare against, and there for would not require an initialization. In this case however, if you are not diving at sea level, you will get a false reading on depth, unless you compensate for altitude.

The Differential would require a connection to the surface to compare to the pressure at depth, and return a value that is in relation to the difference detected between the two.

Does anyone have any background in this? Am I on the right track? Can anyone provide more specific information?

Thanks,
"KR2_Diving"

Hey Ryan,

I am doing the very same research at the moment, and I'm currently looking at this type of sensors
http://www.meas-spec.com/product/t_product.aspx?id=6727

As they're used in divers' computers.
I'm trying to source them in Europe, I'll keep you posted if you're interested

Have a great day
Regards

Alain

Edit: spelling mistakes

Hey Gumma!
Do you have any more details on how you got your depth sensor to work out? Any pics?

Thanks,
Ryan "KR2_Diving"

Will do. I disassembled electronics due to motor testing. I will reassemble it in few days and post some photos and info (if my 2 month baby girl allows it ).

hey gumma, she'll soon be a subby like her dad..

I hope so . My older 3yo daughter wants a pink rod and reel..
Anyhow, this the absolute pressure sensor connected trough differential amplifier to arduino. Voltage difference from sensor is connected to amplifier, amp output is connected to arduino (green wire). Keep in mind that arduino has 5mv resolution for analog input so you need to decrease it to 1mv resolution using analogReference(INTERNAL); on setup. I still didn't calibrate it, i get around 10 mV difference per 1 bar. There's a trimer on amplifier so there's option for hardware calibration of startup point.

Hey Gumma!
Thanks for the pic! I am starting to get the idea! I assume the grey part in the 2nd photo is the actual sensor. Is only one side of this exposed to the water? It is the mounting of the sensor that I can't quite get my head around now...

P.S. After the pink reel, she is going to wan't a Minnie Mouse Bobber!

Heh, i wanted to shoot the pic inside that PVC but i had to play with my minions..Sensor is inside the PVC, sealed only from the outside (yellow 2-component glue), covering wire contacts. Upper side of the sensor is inside the PVC "cap" so i can plug another 2m PVC pipe, pour water in it an calibrate sensor (to do list).

Type in paulsanglingsupplies.uk he's got the complete rod and reel mate,IN PINK..