Once I get my current project off my table, I’m going to start working more on the payload for a high altitude balloon launch. Today, I noticed that Paralllax added a nice little atmospheric pressure sensor. It claims to have a range of about 10 mbar to 1200 mbar, which covers pretty nicely the range expected from a balloon launch (wolframalpha claims the atmospheric pressure at 100K feet is around 11mbar). It includes both SPI and I2C interfaces, which make it easy to pair with any microcontroller, and also has a built in thermometer. Very cool.
They have a bunch of other cool sensors too. Bookmarked for later consumption.
I successfully used the Parallax VTP SCP1000 pressure sensor as an altimeter in my sounding rocket payload. It was hooked to a Propeller, which stored the readings on a microSD card. Nice device – temperature compensated, which is why it has the thermometer on board. I used SPI to talk to it.
I used a US Standard Atmosphere library for MATLAB to calculate the pressure from altitudes from 0 to the end of the defined range, in 10m steps. Then I ran a spline through the points, and used it as a function to calculate altitude from the pressure data. Worked really well (predicted altitude compared well to the radar track data), but probably overkill.
It got less accurate past the 30 kPa limit but still works (until it rails, at a pressure I don’t recall at the moment). The one you list goes down to 1kPa (10 mbar), which is considerably better. Wish I’d had it last year.
More info: http://www.gdunge.com/2010/04/09/the-fachaba-project-is-complete
Thanks for the info, Doug.
Yeah, it’s a bit tight for my ideal 100K flight (it will be operating close to the rail at the apex) but it should give great data over the vast majority of the flight, and I’m hoping to have other means for determining altitude. I’ll probably be ordering one soon.
When you are ready to research trackers, I would suggest BigRedBee. Durable, dependable, and customizable. We have used them on our flights. Disclosure: the designer is a friend of mine, but his product is top notch. http://bigredbee.com/blgps_2mhp.htm