Homebuilt ROVs Forum

rovdude wrote:Maybe... just a thought right now, have the sensor in a bag of air. The air in the bag, I would assume, would have the same pressure as outside the bag. As long as the bag is not completely fillled with air, I think it would proportionally and directly react to pressure. Or put the sensor in a waterproof bag without excess air. Not sure, just spitting out ideas.

air compresses, so the bag would be smaller when the pressure increases, but it could work.
i would rather try the same with oil, oil does not compress, and is often dielectric, so it should not affect the exposed wires.
see the concept of "pressure compensation" here: viewtopic.php?p=4796#p4796

Thank you... oil should work. The way I got into ROVs is I took a summer class at the High School last summer. We made a Seaperch, and at the end we got to take them to Northrop Grumman's naval testing facility in Annapolis, Maryland. The engineers there said any electronics they cant fit into their waterproof sealed compartments they put in oil, protects the electronics all the same.... Im thinking this might work now!

So what I ended up doing is placing the sensor in the finger of a Nitrile (type of synthetic Latex) glove, putting motor oil in the finger, using a ziptie to temporarily seal it, and placing marine epoxy (I used Loctite)in the opening of the finger to fully and permanently seal it off. I tested multiple types of latexs and plastics, Nitrile being the only one that I tested that is not permeable to oil. But, it works great!

I bought this which will get me just over 1000' of water depth:

http://www.ebay.com/itm/261248772710?ss ... 22wt_1124

I cost about the same as what you got and works the same. They have many pressure ranges available and it can be thread into the pressure housing so you don't use up more wire penetrations. I have done preliminary testing and so far it looks good.

I cost about the same as what you got and works the same. They have many pressure ranges available and it can be thread into the pressure housing so you don't use up more wire penetrations. I have done preliminary testing and so far it looks good.

Wish I found this before! Thanks for sharing, I will keep this in mind for the future! Just as a sidenote, if you don't plan on going to 1000 feet get one with a smaller range because of the error. 2% error on that is 20 feet! But if you do plan on going to 1000 feet that's not too bad.

I bought a 100PSI model from the same seller, so that will serve me to 58m, I thought about the higher pressure ones but then thought about how deep I would actually go.

I soon hope to have some code that will use this sensor to hold my depth and also to report my depth.

It's all baby steps for me.

Today I finally got HELLO WORLD on my LCD, it taken many tries, one small step............

kenl wrote:Today I finally got HELLO WORLD on my LCD, it taken many tries, one small step............

Something with a small step for a man and a giant leap for mankind congratz.

TigerShark wrote:I bought this which will get me just over 1000' of water depth:

http://www.ebay.com/itm/261248772710?ss ... 22wt_1124

I cost about the same as what you got and works the same. They have many pressure ranges available and it can be thread into the pressure housing so you don't use up more wire penetrations. I have done preliminary testing and so far it looks good.

Just got my 100psi sensor in the mail! I wanted to confirm something TigerShark... you say you have threaded yours right into your hull... does this mean that the threaded side is exposed to the water? Have I understood correctly?

Ryan
"KR2_Diving"

These pressure sensors looks interesting.
I have one question though. As I am going to use oil filled and pressure compensated hulls, I will have the same pressure on the inside of my hull as the outside. Will these sensors still work if I mount them through my hull and they have the same pressure on both sides?

I will drill a hole through my bulkhead and thread it from the inside. The sensor will then thread in to that NPT tapped hole and will be on the inside of the pressure housing. I'll take some pictures once I get to that point in a few weeks.

It would work fine if your housing is oil filled assuming the back of the sensor can handle the pressure because it only senses pressure through the hole on the threaded end.