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):
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. *
- Motorola MPX7100A
- The Freescale one
- SCP1000-D01 17bit pressure sensor
- From Dave: MS5534B from intersema.ch: 10-1100mbar SPI device. Only available in US from servoflo.com.
- Freescale MPXM2102
- Freescale MPX4115A
- VTI SPC1000
- TO ADD: http://www.bosch-sensortec.com/content/language1/html/3477.htm
| 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 |