air pressure sensors

Forum 2005-2010 (read only) Hardware Interfacing
1

I got some samples some freescale pressure sensors. (The mpx2202gp and the mpx2200gp) and I'd like to use them with my arduino for pressure readings (maxing out around 20 psi).

These are their spec sheets: http://www.freescale.com/files/sensors/doc/data_sheet/MPX2202.pdf?srch=1 and http://www.freescale.com/files/sensors/doc/data_sheet/MPX2200.pdf?srch=1.

Based on what the product sheets say they take like 10V but have no minimum voltage requirement. I figure 9V is close enough?

Then in the output range chart it looks like (with a Vs of 10V) it'll have a max Vout of only 40mV. The arduino has a voltage resolution of .004 volts (1024 voltage counts in the range of 0-5V where 204.8 counts is ~1V). This means that the lowest pressure differential I can read is about 25kPa. Both ports open to the air should yield a 0V result? Blowing into one port should equal?? Do I need to amplify the signal or something??? If so how do I go about it. I'm currently looking into OpAmp circuits. Is that the right direction?

Please don't take my word for it on any of this stuff. I'm posting this to see if my thinking is correct.

Thanks.

2

So, how about a circuit like this one: http://www.freescale.com/files/sensors/doc/app_note/AN1324.pdf

Would that help??

3

Or maybe I just need one of these: http://www.analog.com/en/prod/0,2877,AD620,00.html

4

I recently sampled a MPXAZ6115A from Freescale. When it got here I just hooked it up to the Arduino's analog input and got some readings, took about 10 minutes to breadboard the sensor and get some readings. With a Vcc of 5V it has a full scale output of 4.7V, so an external amplifier isn't needed.

-j

5

I had bought something similar and it was very tiny and difficult to work with. The port form factor of the ones mentioned in the original post are perfect (esp with there mounting holes and prong dimensions).

6

Heh. These sure weren't tiny. I didn't look closely enough at the datasheet when I ordered; the DIP package is an 8 pin DIP, but it's a wide (0.600) package - twice as wide as the Arduino. The surface mount version was pretty much the same device with the leads splayed out surface mount-style - it's even wider than the .600 DIP package. There is an 8 pin SOIC surface mount that's a lot smaller.

These are probably even better to experiment and prototype with, and I'll fo with the smaller model if I decide to fly it.

-j

7

Ok, I did some hunting around on freescale's website and you are 100% correct. The MPX4250GP is perfect for my application (its like what you ordered, in the large form factor, but goes up to 36 psi).

I just placed an order for this and a similar one the MXP4250AP. Luckily both of these were available for sampling.