Pressure Gauge


#1

Does anyone have any ideas for a cheap water pressure gauge?

I need one that can read up to 700psi or so.

I was just going to get something I can mount in front of the camera (no need to send data).

Even just a device that is somewhat crude that I can throw together that will contract as the pressure increases.

I was thinking of playing around with something like this.

http://www.crwsupply.com/index.html?wscdet_show=400000107000107090108012


#2

Even just a device that is somewhat crude that I can throw together that will contract as the pressure increases.

A balloon :)


#3

I think the original idea was to try and find the pressure sensors used in scuba watches, but not sure how easy it would be to find them.
I checked online and the cheapest pressure sensor I found costs 200 GBP, which would be half the price of the whole thing.


#4

ebay. Secondhand dive computer.

For example

http://pages.ebay.com/link/?nav=item.view&id=150867902982


#5

yeah, but if you want to build 1000s of these ROVs, it becomes difficult to find 1000 used scuba watches one ebay :)

And then you need to reverse engineer the pressure sensor for getting data into the board


#6

Thanks, but that will not go up to my target pressure of about 700psi.

I need double that.


#7

Hi,

have a look at the OSTC (OpenSourceDivecomputer)

http://www.heinrichsweikamp.com/#/en/ostc_2n/

here is the schematic

http://www.heinrichsweikamp.net/en/ostc_2n/schematic_pdf

The Firmware is hosted on bitbucket

http://bitbucket.org/heinrichsweikamp

You can use the sensor ms5541cm as in the OSTC project.

the sensor is valid down to 130m.

regards

Rob


#8

Here's some info on the ms5541cm

http://www.meas-spec.com/downloads/MS5541C.pdf


#9

Yeah, that's a good underwater pressure sensor. I've ordered one already, trying to see if it can be easily integrated with Arduino


#10

Very cool info!

Heard about the OSTC before but forgot about it.

I wonder how the sensor could be subjected to the ambient pressure?

I just thought about a flexible container (not quite sure what exactly, maybe a very small tupperware style one) that could be filled with a non conductive oil (someone mentioned some seed/vegetable oil could work. This would protect the the electronics on the sensor from the water while still delivering the ambient pressure.

Does anyone know how that is done in the OSTC?


#11

>Does anyone know how that is done in the OSTC?

Not exactly but i can ask.

As i can see on my OSTC the electronic is grouted in the housing and thr relevant part of the sensor is in contact with the water.

Maybe we can do something similar to this.


#12

That's what I thought. Question is, how do you seal around the pressure sensor so no water enters?


#13

I've asked Heinrichsweikamp about this topic.

Lets wait for the answer...


#14

Yeah,This is the the recommended way of installing it.

Here from the datasheet: http://www.meas-spec.com/downloads/MS5541C.pdf

SEALING WITH O-RING
In products like outdoor watches the electronics must be protected against direct water or humidity. For those
products the MS5541-CM provides the possibility to seal with an O-ring. The protective cap of the MS5541CM is
made of special anticorrosive stainless steel with a polished surface. In addition to this the MS5541CM is filled
with silicone gel covering the sensor and the bonding wires. The O-ring (or O-rings) shall be placed at the outer
diameter of the metal cap. This method avoids mechanical stress because the sensor can move in vertical
direction.


#15

Hi,

so, now i recieved a answer from Heinrichsweikamp.
The pressure sensor is seald with an o-ring
in a turned part. It is important that the circuit board, where the sensor is soldered on, can stand the 14bar pressure. Best is to have a separate circuit board that is plane mounted on something solid, otherwise the outer pressure will push the sensor into the ROV-housing.

I have a photo of an open OSTC here, how can i add this?


Strange the Toolbar is visible only in Internet Explorer, not in FireFox...


#16

in theory there is a toolbar on top of the commenting textbox... if you use a normal computer.

Doesn't show up on iOS and other mobile devices


#17

Is the sensor the black thing in the middle with 4 holes?


#18

Yes, the black thing with the 4 holes is the sensor.


#19

They've sent me the quote for the sensor: 97€ + VAT = almost 120€ (which makes it almost 150USD).

That would make it the most expensive part of the ROV, accounting 1/5th of the overall cost...

I wonder how diving watches can cost so little given the price of the sensor.

Funnily enough, on Aliexpress (the "consumer" site of Alibaba) shipped from probably the original producer of the part, it costs 23USD + shipping.

http://www.aliexpress.com/store/product/100-New-INTERSEMA-MS5541-MS...

Robert, could you ask the guy of OSTC where he gets the sensor and for which price?

Thx

Simo


#20

Hi Simone,

i got one from Digi-Key its about 23 Euro.

http://www.digikey.de/product-search/de?x=11&y=12&lang=de&site=de&KeyWords=ms5541+cm

The point with digi-key is that you have to order for 65 Euro then shipping is free, otherwise shipping is 18 Euro.

Regards

Robert