Help me with interpreting the data from Raven

[V2rocketeer]

Hello all,

Here is my first flight using a Raven. I was looking at the altitude with both the Accel and Baro and see there is a huge difference. 498' for the Accel and 747' for the Baro. OpenRocket sim produced 789'. My payload section is in the nosecone and the vent holes are in the nosecone as well but behind the shoulder. Not ideal so near the nosecone but without a payload bay that was my only option on this build. I have attached the FIP from the Raven. Ok so which reading or sim do I believe hahaha. Open Rocket sims did not include the camera pod on the side of the nosecone but did include it's mass. Thanks in advance for any help.

[YOUTUBE]oMEyDgsT6jA[/YOUTUBE]


View attachment MPcert30032013.FIPa

 

[CarVac]

Did you calibrate the Raven accelerometers before the flight?

I haven't actually looked at the file, but that's almost always the reason for the discrepancy.

 

[V2rocketeer]

Thank you,, hmm no I did not. I just read that section of the manual too. Is that something that needs doing prior to every flight?

Cheers

Did you calibrate the Raven accelerometers before the flight?

I haven't actually looked at the file, but that's almost always the reason for the discrepancy.

 

[CarVac]

Thank you,, hmm no I did not. I just read that section of the manual too. Is that something that needs doing prior to every flight?

Cheers

I would do it at least the night before every launch.

 

[Zephhyr]

When I open your file using the latest FIP-Devel, it shows the Accel & Baro alt being fairly close 796 & 747.

 

[Adrian A]

Thank you,, hmm no I did not. I just read that section of the manual too. Is that something that needs doing prior to every flight?

Cheers

I would do a re-cal if you see the filtered real-time accel display in the FIP reading outside of 0.95-1.05 Gs when the altimeter is held vertically and still. Or if it's been more than a few months or if the flight data shows that the accel-based velocity<0 flight event happens significantly before or after apogee. Each altimeter is individually calibrated before shipment, but the calibration can drift over time.

 

[V2rocketeer]

Thank you Adrian, I will re calibrate before the next flight

Chris

I would do a re-cal if you see the filtered real-time accel display in the FIP reading outside of 0.95-1.05 Gs when the altimeter is held vertically and still. Or if it's been more than a few months or if the flight data shows that the accel-based velocity<0 flight event happens significantly before or after apogee. Each altimeter is individually calibrated before shipment, but the calibration can drift over time.

 

[V2rocketeer]

When I open your file using the latest FIP-Devel, it shows the Accel & Baro alt being fairly close 796 & 747.
View attachment 124320
View attachment 124321

Zephhyr

I do not understand. I am looking at the same data (I think) and I see the blue scale (Barometric) just under 750 and the black scale just under 490 though the waves are drawn fairly close. I am probably reading the data incorrectly. What is the black scale on the left stating with [Altitude (Accel-Ft)] ???? that is the one under 490 and the one I get if I highlight in the "Parameter Selection" box [Altitude (Accel-Ft)]


thank you for the help!!!

Chris

 

[V2rocketeer]

Zephhyr

:surprised: Hmm I look at your screen pic and it looks different than mine. My Alt in the Accel area is different. I am using FIP Mar 1 2012 19:25:07

 

[Zephhyr]

Check out my thread from a couple months back, about Accel & Baro data displaying incorrectly in the FIP.

https://www.rocketryforum.com/showthread.php?47941-Raven-Accel-Alt-Data-way-off

 

[bobkrech]

There is 1 G difference between the 2 plots accelerometer altitude plots. Is there a place in the setup software where you can can have 0 or 1 g as a setting when the rocket is on the pad?



Bob

 

[V2rocketeer]

Thank you Bob,

You posted exactly what I was trying to ask about. I am very new with the Raven so my noobiness is showing. Zephhyr, I am downloding the Dev vers now and will give that a go next. So If I read your thread correctly Zeph, this means the FIP software is misreading the data , but the data in the Raven is correct? Does the FIP files then show erroroneous data with the Accel each time or only occasionally? Is the erroneous data only with the Accel or can it show up with the Baro to?

Thanks heaps


V2

There is 1 G difference between the 2 plots accelerometer altitude plots. Is there a place in the setup software where you can can have 0 or 1 g as a setting when the rocket is on the pad?

View attachment 124404

Bob

 

[V2rocketeer]

Thank you Zephhyr

I got the Dev version and that shows more acceptable, consistent data. I guess everybody should be using the Dev version? :wave:

Check out my thread from a couple months back, about Accel & Baro data displaying incorrectly in the FIP.

https://www.rocketryforum.com/showthread.php?47941-Raven-Accel-Alt-Data-way-off

 

[Zephhyr]

Glad I could help.

I recommend the new Dev version to anyone I know who has a Raven.

Thank you Zephhyr

I got the Dev version and that shows more acceptable, consistent data. I guess everybody should be using the Dev version? :wave:

 

[Adrian A]

Thank you Bob,

You posted exactly what I was trying to ask about. I am very new with the Raven so my noobiness is showing. Zephhyr, I am downloding the Dev vers now and will give that a go next. So If I read your thread correctly Zeph, this means the FIP software is misreading the data , but the data in the Raven is correct? Does the FIP files then show erroroneous data with the Accel each time or only occasionally? Is the erroneous data only with the Accel or can it show up with the Baro to?

Thanks heaps
V2

This was just an issue with the FIP not taking advantage of the accel offset reading that was calculated on-board, and instead calculating the offset on its own with more limited pre-launch data. It doesn't affect the baro readings.

Thank you Zephhyr

I got the Dev version and that shows more acceptable, consistent data. I guess everybody should be using the Dev version? :wave:

I'll ask Kevin to push this into production so that the option to download and install the new version will come up automatically when you open the FIP.

-Adrian

 

[V2rocketeer]

That sounds good Adrian.

I was testing to see if the static vent holes in my payload would work in the location that they were. My vent holes are in the nosecone shoulder and I thought it might cause trouble for the barometer so I wanted to rely on the Accel for a baseline and see where the Baro was. When I looked at the data and saw the around 200' difference and the Baro closer to the predicted alt I was confused lol. But that being said the Altimeter did it's job excellently and it is good to see that the 2 sets of data are very similar in reality coming from the Altimeter.

Cheers

V2

 

[kjs]

Sorry I missed the move to production last time - if you restart FIP, you should get the updated version.

 

[kjs]

By the way, when you get the update, you may want to read the other post about Norton Sonar 'false positives'... also documented on the original installation page : https://www.here-and-beyond.com/Log.In/Altimeters.htm

 

[V2rocketeer]

Thank you Kevin

I had no trouble downloading the update and it works swell.

v2