Redundant systems in aircraft, satellites, etc... don't use *different* types of circuits in their redundant systems. They use identical components.
I recently designed a power supply for a payload for the F22. Requirements were for N+1 redundancy on the power supplies. Did i use a different power supply for each redundant supply? No.
Being in the U.S.A.F. all those years (22) that's exactly the way we do it. It's the same component carried twice.
How much testing such as Thermal, EMI, Stress, Solder Joints and compatibility is available and required for a power supply that is used for an F22 payload? How many other engineers looked at the design and testing?
Or how much testing went into any aircraft component USAF of Civil aviation?
My point is this is a hobby, many of the engineers that have designed products used in this hobby are REAL Engineers and know how to design a product and possible understand risk assesment. However, there is always something unknown. How does each altimeter company test their product? If the appropriate validation testing has been accomplished, don't you think that information would be published with the altimeter? Maybe it is and I have not seen it.
I personnal believe the following (as applied to high powered rocketry):
1) You need to fully know and understand the altimeter that you are using. How will it react to known situtations. What are it's capabilities. What are it's limitations, ect.
2) If you have a need for dual, redundant, backup or what ever you want to call your systems, then you should consider using different devices, to possibly eliminate similar failure modes.
3) Check and recheck all connections, continuity, switches, power and any other appropriate subsystem for your rocket and electronics. (I include recovery components)
4) If something does not look or feel right, it probably isn't. Stop and correct the issue until you know it is right.
5) For most normal flights, if you have good electronics and trust them, why do you think you need to have a redundant system?
6) If you have a high value project; Clustered motors, camcorders, high altitude flight etc. You should consider adding an alternate recovery system, it is generally a very low cost to add a second altimeter when compared to the cost of a big or complex project. (Cheap insurance) I generally do not consider duplicating the staging or motor ignition systems, only the recovery electronics.
7) Get some second opinions to your design or process. This is sometimes humbling, however it can be very constructive.
8) ground test, Ground Test, GROUND TEST
This thread was started as a comment regarding pricing of very common and highly recommend altimeter (Perfectflite MAWD). I do not own one of these, however I too believe that they are a very good product and have recommended them to several individuals. They may be one of the best Barometric Only, Dual Deploy altimeters available. The price actually seems to be very reasonable to me.
If you have other requirements for a rocket, then a basic MAWD may not meet your criteria and you may need to use a product that has the capabilities that you require: programablilty, additional channels, accelerometer, flight recording, telemetery and such.
AKPilot, good luck and have FUN with your L3.
IMO, your experience may vary
John
