What kind of sensure pressure for extreme environment?

Other Hardware Sensors
1

Hi all, what kind of pressure sensor do you recommend for a project operating at 20 bar ( 290 psi or 2000kpa)?
The sensor must be absolute, not in smd tecnology and must be work in water.
Any idea?

thanks in advice

Marco

2

What's the budget?
What temperature range, resolution, repeatability and accuracy is required?
What sensors have you looked at so far?
The web is full of industrial pressure sensors, some expensive, some very expensive.

3

Capacitive disk / diaghram or strain gauge.

4

The project is for a dive computer for rebreather equipment...so
Salt water
temperature range appropriate to the marine environment
20 bar for pressure
budget 100$
dimension some cm
may be analog or digital but must measure the absolute pressure. Since this is a prototype and I have not professional equipment that I would not smd.
I see the project diveduino so nice, this project use intersema pressure sensor. I also have that type of sensor but I find it very difficult to solder the pins so I was wondering if you could find some other type of sensor.

best regards
Marco

5

It seems that when I have looked for inexpensive pressure sensors with good performance they employed MEMs and were all surface mount, although many of the surface mount sensors from Freescale are very easy to solder by hand. Just because the sensor says MST in the catalog do not discount it immediately look at it and then Google surface mount hand soldering or something similar.

6

A cheap stereo microscope will cost about $100 and will make surface mount soldering much easier.

The following teardown video will give you an idea about what goes into building a safety critical waterproof pressure sensor system.
It isn't for underwater use, but the principle is the same.

At 20 bar anything with air in it will be crushed. This includes electrolytic capacitors, voids in components etc...
Truly waterproof pressure resistant containers aren't cheap. If it leaks will the electronics survive?
Do any of components behave differently at elevated pressures? The manufacturers might not be able to provide that kind of info unless you look for aerospace grade components.

7

Another way to destroy electrolytic caps! But surely in a marine environment you use pressure-resistant enclosure for the electronics because otherwise salt water will get in? Or is this all potted-up in resin?