wiki/ avionics/ Pressure Sensors

If you're looking for current information, take a peek at the 2009PressureSensorDesignProject.

Older Information

We want to use a pressure sensor as a barometric altimeter in our avionics system. It takes the local pressure inside the rocket (or, through a special skin port if we ever manage to build one of those) and converts it through a pretty nasty equation into meters above sea level. We take this altitude and plug it into our data fusion model as yet another source of noisy data.

Of course, above about 80 km there's no atmosphere, so this sensor is only good for 'on the way up'.

Range Needed

We used Holly's pressure vs. altitude simulation code (part of the larger event-driven simulator code) to calculate pressure as a function of altitude. Here's our theoretical pressure vs altitude data set and a nice graph (generated with this gnuplot script):

Theoretical pressure vs altitude graph

A few points of interest:

Altititude pressure (mbar) pressure (kPa)
Sea Level 1013 (1 bar!) 100
24,000 ft (last launch of LV2) 395 39.5
75,000 ft (design limit of LV2) 36 3.6
100,000 ft (most FAA waiver limits) 11 1.1
84 km (280,000 ft) ~ 0 ?
Space (100 km) very close to 0 ?

So we clearly want a pressure sensor that goes from 1013 mbar (sea level) to 0 mbar (space). If we can't find one that goes to 0 mbar, we want one that goes at least to ~ 10 mbar.

Pressure Sensors We Found

All this information and associated data needs to be verified.

Mfr Model pressure range(mbar) pressure range (kPa) Price Vendor
Motorola MPX7100A 0 -1000 0 - 100 ? ?
Intersema MS5534B 10 - 1100 1 - 110 ? Servoflo
SMI SM5430/SM 5470 0 - 6800 0 - 689 ? Servoflo
Freescale MPXM2102 0 -1000 0 - 100 $6.48 - 11.49 DigiKey
Freescale MPX4115A 150 - 1150 15 - 115 $14.94 - 18.27 DigiKey
VTI SCP1000-D01/D11 300 - 1200 30 - 120 $ 12 - 47 DigiKey
SparkFun SCP1000 300 - 1200 30 - 120 $54.95 SparkFun