Altimeter cloud: Flight 324

Flight summary

Altitude

Apogee

276.73 Meters

Time to apogee

7.49 seconds

Velocity

Max ascent

89.74 m/s

Max descent

-10.73 m/s

At burnout

68.030 m/s

Landing velocity

-6.460 m/s

Descent velocity

-10.170 m/s

Ejection velocity

4.52 m/s

Acceleration

Max ascent

9.99 G

Max descent

6.59 G

Max during burn

9.99 G

Average ascent

0.03 G

Average burn

4.21 G

Times

Burnout (first)

1.93 seconds

Apogee

7.49 seconds

Possible ejection

6.853 seconds

Landing

46.46 seconds

Output #1 ON

0 seconds

Output #1 OFF

0 seconds

Angles

Launch pad tilt

5.54°

Max tilt to burnout

1.38°

Launch roll

1.27°

Launch pitch

-5.37°

General

Upload date

10-Jul at 10:18

Data samples

1967

Total recording time

60.800 s

Average samples/s

32.3

User notes

Test rocket flight on a Klima D9 motor on a slightly modified Klima Pegasus rocket.

It did land in the tree just by the launch pad, so at least we know how high the tree is now!

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Youtube video

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Device information

Mercury V1

This flight was flown on a Mercury V1 altimeter.

Hardware version

1

Software version

1.2B

Manual / Info

88

More from this altimeter

1

#Merc2582

Motor burn

This is the accelerometer output magnitude for the period from launch to burnout. You can check this against your motors thrust data on thrustcurve.org.

Flight settings

This is a snapshot of the settings that were used for this flight. If you want to configure the settings on your own device, pop over to the My devices page and then Configure settings on the device.

Forecast pressure

The forecast pressure tells the altimeter your altitude above sea level. This can be used to fine tune high altitudes, especially if you're launching from a high altitude above sea level. It's not absolutly essential to do anything with this, you can leave it on the default 1013 mBar average pressure should you choose.

1013 mbar

Launch detect

This is the altitude above the launch pad altitude where the altimeter will trigger itself into recording / flight mode.

The altimeter keeps a constant average of the pressure while waiting for launch, it uses a simple algorithm and the pre-flight buffers to do this. The most recent 120 samples (~4 seconds) are ignored so your pre-trigger altitude won't effect the ground baseline.

For almost all uses we suggest keeping this on the 25 Meter (~82 feet) default settings. If you want to test your altimeter by throwing it in the air, or are planning a very low flight you may want to lower the setting.

25 meters

Sample rate

This is the samples per second that the device will record.

32 per second
The device will record 32 samples per second for around 5 minutes and 15 seconds maximum flight time and is suitable for most flights we would imagine.

16 per second
The device will record 16 samples per second for around 10 minutes 30 seconds maximum.

11 per second
The device will record 11 samples per second for around 15 minutes 15 seconds maximum.

Hybrid mode
This will record at 32 samples per second for the first minute and then 16 samples per second after this for around 9 minutes and 20 seconds maximum per flight.

Note: The time quoted is the maximum per flight not the entire device storage.

32 per second

Recording stop

This setting is how the altimeter decides to stop recording. You can choose either 300 or 600 samples stable or it will record until it's 10000 sample limit unless you press the BUTTON in Manual stop mode.

The samples stable method waits for the devices altitude not to change for the set number of samples. This is defined by not changing by more than +/- 1.0 meters for 98% of the samples, it's a reliable method to stop the recording after landing within 8-10 seconds (300 sample) or 16-20 seconds (600 sample).

Auto: 300 samples stable

Oversampling

Oversampling is a internal setting of the BMP 390 pressure sensor. It is how many samples are taken for each reading. By taking multiple samples for each pressure reading the altimeter reduces noise and increases the resolution of the output.

The sensor can run at 50 samples per second in 4X mode, so we suggest leaving it in this mode as it will offer the highest accuracy.

4X Oversampling

IIR filter

The IIR filter is another internal sensor for the BMP390 pressure sensor. It is a Infinite impulse response filter used to enhance pressure measurement accuracy by reducing noise. It's primarily for smoothing out rapid pressure changes.

We suggest not setting this too high as it will cause delay to changes in altitude if set very high.

COEFF 3

Pressure filter

This filter is a software Kalman filter that runs on the altimeters processor.

The Kalman filter uses a prediction step based on a system model and then a correction step using new measurements to refine its estimate, it creates accurate most certain results from data with noise in it.

Kalman 2 (default)

Lockout time

The Lockout time is how long the altimeter should stop making decisions and taking actions if it detects unusual high speed altitude changes that are unexpected.
These false readings can be caused by ejection charges (if the altimeter is in the same compartment as the motor ejection gases) or even when you transition to Mach speeds and can give false readings of altitude changes.

When these events are detected the system enters Lockout for the specified time while it stabalises. This effects things like triggering the output, or calculating other data.

750ms

Lockout change

This is how we detect a lockout. If the pressure changes by this much in a single sample downwards (pressure increase, lower altitude) then it's likely to be a false reading. Multiply the setting by 32 to get the speed in meters per second that it will trigger at.

1.5 meters

Sync sensors

The filters on the pressure sensor can cause it to lag very slightly behind the Accelerometer and Gyroscope data. The Sync sensors option detects how far out of sync these sensors are. It then corrects the Acceleration and Gyroscope readings to match the pressure sensor.

ENABLED

Orientation

This is the orientation you intend to install the Altimeter in your rocket. It's needed to ensure completly accurate angles and orientation charts and reports. Check out the Manual for more information on this.

Upwards (text up)

IMU filter

The IMU filter, or fusion filter takes the data from each axis of the Gyroscope and Accelerometer to calculate the Pitch, Roll, Yaw and tilt angle from vertical. These filters can build up some discrepency over time so it's important to calibrate your sensors to minimise this.

Madgwick 6-Axis

Launch ALP

This is prevention against accidental launch detection.

With this disabled the launch is based only on pressure and something that creates a low pressure can trigger the flight by accident. For example pulling your nose cone off can even trigger it.

With this enabled the rocket also needs to have seen 8 samples (0.25 seconds) of acceleration above this setting in the last 3 seconds as well as the pressure drop to trigger. There is a backup trigger of 1.05 seconds of altitude being above the launch detect setting too.

There are very few situations where this option would cause issues, so we suggest leaving it on.

Disabled

Output settings

This is a snapshot of the settings for this flight to control the Mercury's output.

Output 1 enabled

Disable or enable the output from being able to turn on or off.

ENABLED

Output 1 trigger

After apogee (altitude)

This method triggers when the altitude drops below the set altitude after apogee is detected.

After apogee (time)

This method triggers the defined seconds after apogee is detected.

After launch (altitude)

This method is activated if/once the altimeter exceeds the set altitude after launch.

After launch (time)

This option triggers the defined seconds after launch is detected.

After burnout (time)

This method triggers the defined seconds after burnout is detected.

After apogee (altitude)

Output 1 time on

This is how long the output should trigger ON state when the rules are met.

2000ms

Output 1 altitude

This is the altitude to trigger at if using a trigger method that works on altitude.

For example if you set this to 75m and After apogee (altitude) for the trigger then the output will turn on at 75m on descent above the launch altitude.

0 meters

Output 1 time

This is the time variable for output triggers that work on time.

For example if you set this to 3 seconds and After apogee (time) as the trigger then the output will turn on 3 seconds after apogee.

0 seconds

Altitude lock

Altitude lock is a safety feature that prevents the output from triggering if the altitude is below this level when the rules are met.

0.00 m

Tilt angle lock

This is another safety feature. It can be used to disable the output if the rocket has gone too far from vertical.

For example if you set the tilt angle lock to 40 degrees then the output will not fire if the rocket is more than 40 degrees from vertical. To disable set this to 0.

0.00 °

Sensor calibration

Here are the sensor calibration offsets used during this flight.

Gyroscope

0.000°

Accelerometer

0.000 mG