Easy to use air pressure sensors

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artswan

Member
For beginners or others looking for easy to use air pressure sensors, may I recommend the Freescale/Motorola MPX series of air pressure sensors. I have used several of them (MPX4100, MPX4115, and MPX5100) and have found them very easy to use with the A/D input of Picaxe, PIC, AVR, and other lines of microcontrollers. They each come in several subscripts (A for absolute, D for differential, etc) and you can find all of the information from their datasheets and online searches. The main things I looked for were full scale output swings to near the 5 volt rail (4.25V+). This indicates internal amplifiers and no need for external differential amplifiers (pain). Some (MPX4115A) are specifically for applications such as altimeters and such and some others (MPX5100) specifically describe their use with microcontroller A/D inputs. With mine, I simply use the Vcc, Ground, and V+ output. You can buy models that are compensated or uncompensated. Most of the data sheets give transfer functions on how to convert the analog outputs to kPa and such. Also, if you want, with these simple and straighforward analog outputs, you can even hook them up to a simple multimeter, get the direct voltage reading and convert in your head or on paper. I love these things! :)

By the way, you can pick up these gems at such outlets as Digikey, Mouser, Newark, etc. They usually run in the $10 to $20 each price range.
 
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moxhamj

New Member
I'll second those comments. I've been using these sensors for a number of years and they work great with picaxe. The scaling is always a good maths exercise. I've also used them for water level sensing (10 metres of water = 1 atmosphere = 14psi = 100kpa). The sensors come in lots of different pressure ranges so you can get one that goes full scale over the values to be measured.
 
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Texy

Senior Member
.....and if picaxe supported the natural log function to calculate results, then there would be no need for a lookup table;)

Texy
 
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MFB

Senior Member
The definition of ‘easy’ depends on your level of expertise. Being stronger on the hardware side than software, I would find the above analog sensors easer to use but a competent programmer would certainly find one of the smart sensors with I2C or SPI digital ports much easer to interface and (more importantly) calibrate.
 
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InvaderZim

Senior Member
Horray for viral marketing!

Actually, I've been looking at the Honeywell TruStability line of P Sensors. They have really high overpressure ratings (the pressure at which the sensor is damaged). Most sensors take damage at like 1.5x max reading, but some of these sensors are more like 10x, which means they're more stupid-proof and tend to not lose calibration so bad. The burst rating (the pressure at which it actually blows apart) is higher too. I think they have fractional PSI sensors with overpressure ratings of ~10PSI. And they are available with on-board amps, calibration, temp compensation, and digital interface (I2C or SPI). Unfortunately, they're brand new, and so aren't very available or cheap yet :( . But I'm hoping that'll change in the next year; I've always wanted to dink with one :p
 
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artswan

Member
Nope, not marketing for Freescale. :) Just found these sensors after jacking around with some cheap surplus sensors that required external amplification, conditioning, etc. and have been very pleased with the ease of use of the Freescale sensors. Also, I like working with analog outputs that I can hook up to A/D microcontroller inputs. I am more hardware oriented than software and like to get my projects up and running quickly rather than spend a lot of time coding. ;)
 
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Texy

Senior Member
Err OK, thanks for sharing:cool:

I got a couple of free samples of the MPX4115 a few years back. Not sure if freescale still supply freebee's to the common people any more.

Texy
 
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