Well that is about the most far out idea I've seen posted around here. I have no idea if the Arduino could handle that pressure or not. At first I assumed that the RF could not penetrate the tank walls, however if you make the whole tank the antenna, then maybe. I really don't have a clue Would an Arduino even fit through the tanks connection nipple, or are you talking a smaller version? Also you would have to make sure your pressure sensor is of the absolute pressure sensor type rather then the two port PSIG type that uses ambient pressure for it's reference leg.
Any reason you just don't connect a pressure sensor at the high pressure outlet fittings, seems a lot more practical.
Not to discount the idea, but I second retrolefty's suggestion. I don't know whether it would survive the 3000psi inside the tank. I don't know if they design the chips with that kind of pressure in mind. If there is any mind of air space left over from the manufacturing process, it would imagine you would crush the chip(s). The radio transmission would most certainly not make its way out of the tank. I am almost certain of this. I'm not an expert on radio, but I think the tank would act as a ground plane, and absorb all of the signal.
How would you attach the assembly to the inside of the tank?
I would even recommend attaching it to the low pressure fitting.
What's the application? I ama scuba diver myself, so I would love to see what you are trying to accomplish.
I would also worry about potential flammability, or even chemical reactions, in the high pressure environment, particularly if the scuba tank is going to be used for scuba. You might wind up suddenly trying to breathe a lot of stuff you'd rather not
Serendipity! I cannot find a link but just yesterday I was reading about deep-sea vehicles and electronics. The biggest problem is internal air pockets. Apparently, crystals have a tiny air-gap inside. When subjected to high pressure, the two halfs of the crystal are crushed together. Even if the rest of Arduino is OK, the crystal probably won't survive.
As a fellow diver, this sounds like a really good way to purposefully poison your own air supply and DIE. Only thing I want in my tank is air. Think if some tiny part jams up the piston assembly in your first stage and it stops working.
Unless you have some unstated reason for putting it in the tank that doesn't require you actually breathing off of it.
Depending on your first stage if you have an available high pressure port, you can run a hose to that, then have your sensor connected to the end of that hose and keep the project box in another location (BC Pocket, bottom of tank?).
As for your project box, its going to have to be sealed and filled with a non conductive fluid that has a very high resistance to compression, linseed comes to mind, with ZERO air bubbles.
It's not just the arduino standing upto the pressure you have to worry about, what about your power source? being inside a tank it's obviously going to be some form of battery, lipo would be a bad choice, they would combust for sure... not really sure what sort of power source you could go for that would survive that sort of pressure.
What about making your device water proof and "teeing" a pressure sensor into the air lines or regulator?
in my simple mind, i allways thought that air was more or less liquid at this preassure
200 bar? Nope, still gaseous.
Really, really, bad idea though.
Please, as a fellow diver, don't even experiment.
I don't know why you want to put it inside the tank, when RF transmitters are already available to fit on the HP ports of your first stage.
i was going to use the metal body of the cylinder as the antenna
well it wouldn't work because for an antenna you need two conductors insulated from each other. The normal stub type antenna has a second connection to a ground plane normally caused by the objects around it. Using only one totally enclosed connection is the RF equivalent of not connecting the grounds together on two power supplies.
I doubt you could beat the price of this whatever you do:
Maybe a cool project would be to make something that can receive the signals from suunto pressure transmitters? Wonder what sort of range could be gotten with a big boat mounted antenna? Would be nice to have the dive boat waiting for you when you surface after your safety stop.
The water would just ground out your RF signal instantly anyway.
Depending on how deep you dive, it may be a smarter idea to invest in some very long wires, and only have the pressure sensor under with you, and the Arduino and power supply floating above the surface or sitting in the boat etc.. Even under the water there is a huge amount of pressure potential.
the application is not diving but i too am worried about contamination in case it causes it to burst
the application is a wireless read out of a high pressure thing
for the pressure gauge i was going to use a car tyre sensor, these are rated to about 250bar - i might not even need the arduino if i can find a way to pick up the signal but am i not sure if i even can yet
as for the crystal could a ceramic one survive?
as for the battery i am going to see how the tyre pressure sensor is powered and take it from there
i will not be breathing the air and i will not be going under water
the RF signal will be travelling through about 5mm of steel about 6" in total to the receiver
i think this would be really cool if i can pull it off
the RF signal will be travelling through about 5mm of steel
No, it won't. RF signals will not travel through steel, or any metal for that matter. You'll need to find a way to get the RF signal out through a non-conductive window. You can't use the tank as an antenna, either, because there's no way to have separate connections for RF and ground.
if it's not going underwater - why on earth would you place the electronics inside the tank? just tee off the connector into a pressure sensor such as: