pressure sensor: air conversion to water

[stoene]

Hello fellows,
I've got a sensor that is made for gaseous media and I plan to convert it to water. Norbert Brüggen suggested (book) silicon oil. However, my little town has no such animal (or it is overly reclusive). Where can I get this type of oil? On top of that, how do I keep it from leaking out? My sensor is super accurate sensor with 1/4 inch resolution. I ordered it some time ago and have forgotten the maker. Mouser.com has my records so will have the specs on Monday. Thanks for any info.

[dietzer]

Hello Stoene,

Many hobby shops that

Hello Stoene,

Many hobby shops that stock R/C car parts sell some kind of silicon oil. I have no idea how it would work on pressure sensors.

Carl

[fgroza]

The oil is used for

The oil is used for R/C car shocks. It comes in different viscosities. The laoger the number the thicker is is.
Frank

[tknofile]

Hi,


I have successfully used

Hi,


I have successfully used many sensors in my boat and am wondering what kind of output your sensors will be providing. If your system can handle serial 8-bit data then you should use a motorola 5050DP (this isn't the whole part number but it should be enough to track it down). this sensor has 2 ports. I glued one shut at 'sea level' and put a piece of tubing on the other that connects to an 1/8 fitting on the hull. The sensor measures the air pressure in the tube. The external water pressure compresses the air in the tube and hopefully never gets all the way to the sensor. I have used this sensor with an 8-bit analog to digital converter (I think its from national semiconductor ADC0831). This outputs the 8-bit data stream come from this chip and go to the on-board computer of your choice. With the 0831 you can set the resolution to whatever you want. I have mine set to .2 inches for each data point. With an 8-bit device you are limited to 256 data points which allows me to read depth to about 4 feet. Good luck
rick

[stoene]

Hey thanks for the replies,

dietzer

[color=#000000]Hey thanks for the replies,

dietzer fgroza,
I found some Silicon oil at the LHS. I bought the thinnest kind with the idea that it would most easily shed air bubbles before sealing it up. I also bought some tiny balloons for membrane.

tknofile,
Does the sensore output linear data by using air? It seems that the air itself will absorb some of the pressure giving a e^t type of shape. If so, did you compensate in your PIC? My sensor outputs at 0-100mV over 0-5psi and is an absolute sensor( the differential port was left off at factory ). I'm using a OOpic microcontroller as the brain. It has several AtoD ports, 8-bit, to capture data. I'll also have a home-made tilt sensor (unless you guys know of something reallll cheap/ I'm a starving college student) using Leds. I have the stuff to make Norbert's liquid inclinometer but I figure I can use the OOpic to filter out harmonics of the Led setup. I plan to use stepper motors to drive the piston tanks so won't need feedback resistors.

So you just have a tube pointed downward that has air trapped into it. I guess an analogy to help me understand how this could work would be]