Accelerometer-only Apogee Loggers

The Rocketry Forum

Help Support The Rocketry Forum:

Gip-Gip

Active Member
Joined
Jul 2, 2020
Messages
32
Reaction score
3
Hello! I'm currently making a bluetooth apogee/gforce logger using 2 accelerometers(1 watchdog in 16g mode, 1 high-accuracy that varies between 2-16g mode) and 1 gyroscope. I'm curious as to if there are any other apogee loggers which use only accelerometers, and if their accuracy is as good as the barometer ones by any stretch of the imagination. I'm only looking for an accuracy of +-1m, and in theory with the datasheet accuracy of the accelerometers that should be possible, in theory. I just want to know if anything like this has been attempted before, and if it's been a massive failure or not

When I'm done with the schematic I'll post it here

LIS3DHTR accelerometer
I3G4250DTR gyroscope
 

gtg738w

FlightSketch - flightsketch.com
TRF Sponsor
Joined
Dec 27, 2018
Messages
276
Reaction score
249
Acceleration based methods will accumulate error since you are integrating twice to find altitude. Unless you get a perfect attitude solution from the gyro and are only integrating over very short time scales you will be unlikely to get 1m accuracy. Barometric sensors can make a “direct” reading but your altitude is still subject to the standard atmosphere approximation. So either method is probably not going to hit your accuracy goal. Most cases it won’t matter though and you won’t even know it unless you have a backup system like a radar altimeter.
 

AllDigital

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jun 14, 2013
Messages
295
Reaction score
199
Location
SoCal
I don’t know what you are flying, but you will likely max-out a 16G sensor and then all the following integrations will be inaccurate.
 

Voyager1

Well-Known Member
TRF Supporter
Joined
Oct 23, 2015
Messages
667
Reaction score
215
Location
ACT, Australia
I don’t know what you are flying, but you will likely max-out a 16G sensor and then all the following integrations will be inaccurate.
Yes. It might be useful to simulate the rocket/motor combinations that you intend to use this with to determine what G ranges you are dealing with. It is quite possible that +/-16G is not enough.
 

les

Well-Known Member
TRF Supporter
Joined
Jan 20, 2009
Messages
2,821
Reaction score
445
Unless you have a 3 axis suite of accelerometers, you will also have errors caused by non-vertical flights. A rocket can weathercock due to winds - say worst case it ends up flying horizontal. It will still have g forces from the motor, but not gain altitude
 

jderimig

Sponsor
TRF Sponsor
Joined
Jan 23, 2009
Messages
3,323
Reaction score
738
You can easily claim 1m accuracy because the true altitude at apogee is unknowable with current economical hobby implementations.
 

UhClem

Well-Known Member
Joined
Feb 6, 2009
Messages
1,760
Reaction score
247
You can easily claim 1m accuracy because the true altitude at apogee is unknowable with current economical hobby implementations.
It is even easier if you fail to mention the range. There is a big difference between 1% accuracy (100m range) and 0.01% accuracy. (10km range)
 
Top