hello i am working on a underwater monitoring system, my idea is to hawe a pressure/temp sensor and a light dependent diode as a turbidity sensor, I hawe a pressure sensor that I hawe bought from DX, next time i will buy another one, i did not realise it is a counerfait when i bought it, i have used a code from the arduino page but got some weird results:
Temp
=-0.0511111 1111100
100000 10000000
Pressure [Pa]=16383
100001 10000100
Temp[C]=-0.0511111 1111100
100000 10000000
Pressure [Pa]=16383
100001 10000100
Temp[C]=-0.0511111 1111100
100000 10000000
Pressure [Pa]=16383
100001 10000100
Temp[C]=-0.0511111 1111100
100000 10000000
Pressure [Pa]=16383
i hawe this sensor [http://dx.com/p/meeeno-digital-barometr](http://dx.com/p/meeeno-digital-barometr) ... nge-227072
and use this code: [http://arduino.cc/en/Tutorial/BarometricPressureSensor](http://arduino.cc/en/Tutorial/BarometricPressureSensor)
I am sorry if this is a stupid question, but i kindof am when it comes to programming....
I will post some pictures of the build as it goes along...
And what will the atmospheric pressure of the air in the sealed box be as it goes underwater ? Why ?? As a hint ask yourself what the pressure inside a manned bathyscape at the very bottom of the ocean would be ?
Also the BMP85 reads atmospheric pressure from some high altitude down to -500m, in air. How much more, in air, is the pressure at -500m vs sea level ? Given the pressure in water ~doubles (100% more) every 10m, how deep in water can the sensor read before it bottoms out (assuming the sensor had access to water pressure outside of it’s box) ?
but the measure-range maby a problem if it is correct, because if i am not wrong at -500m it is just over one bar pressure and at 30m it is around 4bars 1bar for each 10m of deapth plus atmospheric pressure…
The important point in that video was the bottle was open. The air pressure inside could change because the outside water could force the volume to change. Your box *could* do the same by adding a diaphragm of some sort to keep the box sealed but allow the water to compress the air inside.
The you’d have the sensor problem. The BMP85 would work for maybe 1m then bottom out. You need a different sensor.
one like the WW-II airplanes used for altitude sensing for adjusting the radio TX power. These were small metal bellows. You can still buy these kinds of things today.
google metal bellows.
Some then tie the bellows displacement to a potentiometer or some such.
I am also hawing some minor problems regarding the turbidity sensor, the readings is quite unstable and it seems to be too little differense in reading from dark to light… i am using a photoresistor and 1,5k pulldown resistor, i hawe seen than many use a 10k resistor, but i did not hawe one… would that be a big difference you think?
esmi83:
MS5541 maby it is good to use a sensor like this?
I am also hawing some minor problems regarding the turbidity sensor, the readings is quite unstable and it seems to be too little differense in reading from dark to light… i am using a photoresistor and 1,5k pulldown resistor, i hawe seen than many use a 10k resistor, but i did not hawe one… would that be a big difference you think?
Random trial and error – you’re probably never going to achieve success this way!
esmi83:
MS5541 maby it is good to use a sensor like this?
Perhaps, there are different versions for differing pressures. How deep do you want to measure ? It's listed as being used in dive computers so I ASSume the sensing orifice is waterproof.
esmi83:
I am also hawing some minor problems regarding the turbidity sensor, the readings is quite unstable and it seems to be too little differense in reading from dark to light… i am using a photoresistor and 1,5k pulldown resistor, i hawe seen than many use a 10k resistor, but i did not hawe one… would that be a big difference you think?
I'm not sure what to tell you. How sure are you about the stability of the readings in clear water ? If the signal is too small, would a more sensitive detector (phototransistor ?) be the solution ?
<LINK_TEXT text=“http://i66.photobucket.com/albums/h254/ … 0e2ff7.png”>http://i66.photobucket.com/albums/h254/edwardmx5/Utennavn_zps000e2ff7.png</LINK_TEXT>