Big differences between Ob-Board data and Transmitted data | Telemetrum V2.0 Board

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LWeissbrot

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Hi dear Rocketryforum,

We are a group of students from the Technical University of Berlin. On 11.4.2022 our hot-water-rocket was launched. We used the Altus Telemtrum v2.0 board to record and transmit the telemetry of the flight. Unfortunately, the recovery system was not triggered during launch, so we are now trying to find the cause of this error.

The recorded telemetry has some inaccuracies and transient patterns. Therefore, the evaluation is more complicated than expected. First, the OnBoard telemetry and the Transmitted telemetry are often not identical and second, there are strange artifacts in both data sets. I have attachet some screenshots to understand what we mean. Additionally, you can find attached the raw (AltOs) datasets of both, OnBoard and transferred data, and a summary of the configuration of the TM board at the launch site.

Some general info about our setup:

  • We connected our pyro igniter for the recovery system to the Apogee igniter.
  • The "Igniter Firing Mode" was set to DualDeploy.
  • The Apogee Igniter Channel was successfully tested 2 times at the launchpad prior to launching
  • Main Deploy Altitude was set to 250m


Thank you very much for your help!

Best regards,
Marco
 

Attachments

  • onboard_2022-04-11-serial-5090-flight-0001.eeprom
    62.1 KB · Views: 0
  • AltOS_Config_LaunchSite.txt
    1 KB · Views: 0
  • transmitted_2022-04-11-serial-5090-flight-0001-via-2425.zip
    259.7 KB · Views: 0
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Thanks for the quick respond!

Do I just write an email with my questions to "[email protected]" or do I need to enter a different thread in the forum? I am not familiar with listservers.
 
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Transmitted telemetry vs the eeprom/onboard data will be different as the onboard data is logged at a much higher rate. Regardless it should be roughly comparable. When I get the chance I'll have a look at your data files later today.
 
Also, what firmware version were you running on the board?
 
I found out recently that the recorded data (.eeprom) isn't what I expected. It shows the raw rather than filtered data. Your flight shows clear signs of this disconnect between recorded and Kalman filtered data. For example, the drogue fired at 9 seconds and the velocity (integrated acceleration) is about 55m/s. (The GUI velocity drops because it switches to numerical differences on the pressure data after the drogue state is triggered.)

The telemetry data on the other hand appears filtered.

The pressure data is wonky which would definitely mess up the filtered data. Check your vents. Kalman filters are great but it requires that the altimeter be mounted in the correct orientation for the accelerometer to work well and it must also be correctly vented for the pressure sensor.
 
Also, what firmware version were you running on the board?
I will try to check the board version once i am back in the lab. The flight was conducted on the 11.April this year, if it helps identifying the firmware version.
 
I found out recently that the recorded data (.eeprom) isn't what I expected. It shows the raw rather than filtered data. Your flight shows clear signs of this disconnect between recorded and Kalman filtered data. For example, the drogue fired at 9 seconds and the velocity (integrated acceleration) is about 55m/s. (The GUI velocity drops because it switches to numerical differences on the pressure data after the drogue state is triggered.)

The telemetry data on the other hand appears filtered.

The pressure data is wonky which would definitely mess up the filtered data. Check your vents. Kalman filters are great but it requires that the altimeter be mounted in the correct orientation for the accelerometer to work well and it must also be correctly vented for the pressure sensor.
Hey Clem,
Thanks for your reply.
When I first analysed the data I saw the drop in velocity and could not explain why it happend. Your explaination makes total sense and will help with my further investigation. I will check the hardware for proper ventilation and report back.

Thanks again!
 
I will try to check the board version once i am back in the lab. The flight was conducted on the 11.April this year, if it helps identifying the firmware version.
It sounds like David identified the probable issue, so getting the firmware version doesn't really make much sense if that's the root cause. But being mindful of what firmware version you're running as well as the bug fixes available in later revisions is a good thing to do with Altus products. And you'll be running the firmware that was applied to the board when it was purchased/shipped. If you bought it from a reseller it's quite possible you're running a very old version and could benefit from updating.
 
It sounds like David identified the probable issue, so getting the firmware version doesn't really make much sense if that's the root cause. But being mindful of what firmware version you're running as well as the bug fixes available in later revisions is a good thing to do with Altus products. And you'll be running the firmware that was applied to the board when it was purchased/shipped. If you bought it from a reseller it's quite possible you're running a very old version and could benefit from updating.
Yea ... I think so too. But I will still try to investigate further. There still are some weird artifacts in the data especially when you export them as a .csv.

Btw. the firmware on flight-day was 1.8.5!
 
Yea ... I think so too. But I will still try to investigate further. There still are some weird artifacts in the data especially when you export them as a .csv.

Btw. the firmware on flight-day was 1.8.5!
eesh, that's a release was from March 2018!
 
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