The MS5607 pressure sensor from Measurement Specialties is probably the most common sensor used in rocketry electronics. It is small, durable, reliable, accurate, and relatively inexpensive. I have used it in the Featherweight Ravens starting with the Raven3. It also used in Altus Metrum products, the Missleworks RRC3, and others.
But something to be aware of is that shining a bright light into it can cause large shifts in the measured pressure. Normally this isn't a problem because our av-bays tend to be closed and dark. But if you happen to have a large vent hole located right next to the sensor, like this 29mm minimum-diameter rocket does,
and you fly on a sunny day, then you can get altitude readings like this:
The red line is the Serial number 2 blue Raven on the left side of the image above. The Blue line is for serial number 8, which had its baro sensor aligned with the vent hole. When the rocket was doing its drogueless tumble, sometimes the rocket attitude put the bright sunlight right on the sensor through the vent hole, and the measured pressure erroneously blipped upward by thousands of feet. The first major blip also caused a spike in the baro-based velocity estimate:
and in this flight yesterday, that triggered the main chute backup logic which deploys the main if the baro-based velocity gets too high, as would be the case with a failed apogee deployment. This backup main feature checks for the descent rate to be persistently too fast before it fires the main chute, and I'll bump up the persistence threshold to ignore a case like this, which I think is a pretty worst-case scenario for this.
This can also be fixed just by changing the rocket to keep the vent holes away from the baro sensor. For my purposes I'll keep my test rocket as it is, to make sure that the main chute backup logic improvements handle a flight like this in the future.
But something to be aware of is that shining a bright light into it can cause large shifts in the measured pressure. Normally this isn't a problem because our av-bays tend to be closed and dark. But if you happen to have a large vent hole located right next to the sensor, like this 29mm minimum-diameter rocket does,
and you fly on a sunny day, then you can get altitude readings like this:
The red line is the Serial number 2 blue Raven on the left side of the image above. The Blue line is for serial number 8, which had its baro sensor aligned with the vent hole. When the rocket was doing its drogueless tumble, sometimes the rocket attitude put the bright sunlight right on the sensor through the vent hole, and the measured pressure erroneously blipped upward by thousands of feet. The first major blip also caused a spike in the baro-based velocity estimate:
and in this flight yesterday, that triggered the main chute backup logic which deploys the main if the baro-based velocity gets too high, as would be the case with a failed apogee deployment. This backup main feature checks for the descent rate to be persistently too fast before it fires the main chute, and I'll bump up the persistence threshold to ignore a case like this, which I think is a pretty worst-case scenario for this.
This can also be fixed just by changing the rocket to keep the vent holes away from the baro sensor. For my purposes I'll keep my test rocket as it is, to make sure that the main chute backup logic improvements handle a flight like this in the future.
