Hi Folks,
I am intending to do some data capturing associated with my SCUBA diving.
I am struggling to find a low cost pressure sensor to allow me to measure depth. I am think a sensor to measure up to about 5 bar or therabouts.
Can anyone help or advise?
Many thanks, Steve
PS I am sure at later date I'll be asking some Arduino related questions for whatever sensor I chose.
Get a Suunto.
If the goal is to have the pressure sensor at the to be measured depth, then you will need an absolute pressure. If it is a standard pressure sensor it will read the difference between the pressure port and the local ambient (i.e. gauge pressure)
I have a Suunto dive computer. How does that help?
Yes that is clear
You said you were struggling to find a low-cost pressure sensor and logger
???
Sunnto dive computer was not low cost and it cannot be used for logging. Certainly cannot be connected to an Arduino later.
I think I may have found a possible candidate:
MD-PS002 Series Air Pressure Sensor
Model Number MD-PS002 Series
Problem is that cheap pressure sensors like that have a mV output,
so you also need an instrumentation amp between sensor and Arduino.
Better look for a sensor with ratiometric 10-90% (0.5-4.5volt) output or I2C output.
Leo..
My Vyper Air logs depth, tank pressure and water temperature, logging every 20 seconds
It cost £200 about 15 years ago. I've changed the battery annually.
I haven't had to spend any time greasing it, or sealing it into a custom enclosure, in temperatures from 4 to 34 degrees.
Pretty low cost to me.
Do you really care about temperature? My dive computer logs it too, but doesn't display it so I looked at it once and that was it.
The company rep said that their engineers figured that there was no need to add a non essential data item for someone already suffering from a three martini effect. And besides, he said "You know when you're cold". 
I felt lucky to find one at all at such low cost.
I've a HX711 module in my 'box of bits'. At the moment that would seem a suitable candidate to interface between Whetsone bridge sensor and uC.
Of course - General Gas Law and all that
Useful for remembering where the thermoclines actually were
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