Amplified low pressure air sensor? 0-2psi

Hi all,

I have a project where I am filling three bladders with air using small compressors. I switch the compressors on just using a simple transistor, and now I’m looking to setup control with a low pressure sensor. We need roughly 40-60mmHg of pressure. I am having difficulty finding a amplified pressure sensor that can handle that low level of pressure.

I understand I could use a INA125P to amplify the signal to the 0-5V range, but that would add a large circuit to our project since we need 3 of them. We need to box this all up so I would prefer to not need a secondary amplifier circuit.

So… anyone have any good ideas or know of ones I could buy? Looking for pin hole connection, not surface mount. Honestly I don’t care if they are super accurate, but I cannot afford to spend a lot of money on this. The only ones I like so far are in the $80 range which is pricey. I would be more comfortable with <$10

I suppose the pressure could go slightly higher, maybe 3PSI, but I’m worried about losing resolution if I get too high.

Thanks for your help!

Suitable for tube connection to pressure source: The MPX5100 family have a 0V…5V output.

On eBay at he moment thee are lots of these : APM2-5-MPXV7002DP Breakout-Board.

It's a differential sensor, but you might make it work.

Pogo.

.. but that last variant handles only +/-0.3 psi (0.021 bar)

Hello,
I'm also looking for a solution like this so I have been following this topic.
Correct me if I'm wrong but according to a google search 40 - 60mmHg is 0.7735 - 1.16 psi (0.0533 - 0.08 bar), so the MPX5100-family should do the trick, right?

I'm looking for a similar sensor that can read 5 to 10 bar (about 72 - 145 psi, 500 - 1 000 kpa) and found one defined SPD100G. It outputs only 100mV but reads between 0 - 6.5 bar, has an acceptable offset and is in a good price range. Is it possible to map the output values so it can be used with an arduino uno anyway?

with a one like this http://www.ebay.com/itm/Weighing-Sensor-AD-Module-Dual-channel-24-bit-A-D-Conversion-HX711-Shieding-/400563601604?pt=LH_DefaultDomain_0&hash=item5d437380c4
It will do just fine.
You can also build your own amplifier with dual rail-to-rail opamp and a couple of resistors.
(last option for full control of gain)

knut_ny:
.. but that last variant handles only +/-0.3 psi (0.021 bar)

Doh!

Sorry to mislead you all. I spotted the 3, missed the 0.

Note to self: put glasses on before typing...

Pogo.

After a lot of googling there is one last thing I want to share that's might be of guidance, this web page.
They explain that a differential pressure type sensor is to prefer so that any changes in the climate do affect the sensor and the reading will be more accurate. It also mentions how much water pressure builds up depending on the height, 9.8067kPa per meter It sounds realistic, but I can't answer if that's accurate. I'll leave that to someone else that still remembers the physics from school! :grin:
Kayne Richens has done a nice project to measure water level with similar sensors.

i am making blood pressure measuring device using arduino nano v3.3 . i am using air pressure sensor (MPS20N0040D-D) to measure the air pressure however the output of this sensor is bit low so i need to amplify the output voltage of sensor. i tried dual voltage amplifier LM358n but it did not work for me. so can anyone suggest me any good or ready made circuit.
what about HX711? does it help me to measure air pressure ?

any help will be appreciate.
thanks