Perfectflite minialt/WD question

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davalf

davalf

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I flew my rocket this past weekend with the perfectflite minialt in it. My nose and payload section got separated from the booster and came down in a flat spin with no chute. I am assuming it lost power when everything separated. When I got the rocket back home I powered the altimeter up and it is reporting 20000' which I know the rocket did not reach. I think it reached about 5000'. A fellow club members rocket had 2 of the same altimeters in it and it was doing the same thing. Both of them reported 20000' which his rocket did not even come close to. Anyone have any ideas?

Thanks
Dave
 
Did you download the data?

I've only flown mine once & haven't heard of this as of yet...

I mainly fly the ARTS as main deployment.


JD
 
I would download the data. Occasionally, you will get odd spikes in the barometric trace (this is a statement in general - I don't own a MAWD). It should be pretty obvious in the downloaded trace if there's something horribly botched in the altimeter, or if it just has an odd spike at ejection or something like that.
 
I do not have the cable to download. The person who had the same problem does. I will wait to see what he comes up with. Thanks.

Dave
 
I sometimes see spikes in my data at ejection. Here is an example of a spike on the Perfectflite Alt15K flown on a minimum diameter rocket on a D12-7.

Altimeter Spike.jpg
 
Mine did that once. My rockets chute got tangled and the rocket landed hard. The Perfectflight was reporting 20,000' as well. I think it is because of the hard landings with these things. Somehow the shock of landing messes up the readings they are taking and they just report 20,000'

...Fudd
 
Probably not the issue in this case, but I've had some goofy readings with a MAWD before that I traced to the vent holes not being large enough.
 
skycopp said:
Probably not the issue in this case, but I've had some goofy readings with a MAWD before that I traced to the vent holes not being large enough.
Click to expand...

Sunlight on the baro sensor will cause very large fluctuations in the baro output. If you exceed the range of the device the PF might just report its maximum value.

If you use very small vent holes you will have created a pin-hole camera in addition to an av-bay. If the angles are right you can image the sun on your baro sensor. If the downloaded values shows wildly oscillating baro altitudes that is probably what happened.

A good practice with baro altimeters that use the ubiquitous MPX4115/6115 series is to make a small shade over the baro sensor with a small arc of masking tape (sticky side up).
 
Its happened before with my MAWD. I assumed it was from an over energetic ejection charge against the bulk plate of alt bay, causing a spike in pressure in the bay. I've never had a problem with working after though.

Ron
NCR
NAR L2
 
davalf said:
When I got the rocket back home I powered the altimeter up and it is reporting 20000' which I know the rocket did not reach. I think it reached about 5000'.
Click to expand...
I've had this happen. The power to the altimeter was interrupted and it reset. Download the data, you will have the correct data during the time before the reset. There may be some of the old data from a previous flight appended to the new data. The graph will be scaled to 20000' but you can find the actual apogee by examining the data in list format. The altimeter will work fine on the next flight.
 
jderimig said:
Sunlight on the baro sensor will cause very large fluctuations in the baro output. If you exceed the range of the device the PF might just report its maximum value.

If you use very small vent holes you will have created a pin-hole camera in addition to an av-bay. If the angles are right you can image the sun on your baro sensor. If the downloaded values shows wildly oscillating baro altitudes that is probably what happened.

A good practice with baro altimeters that use the ubiquitous MPX4115/6115 series is to make a small shade over the baro sensor with a small arc of masking tape (sticky side up).
Click to expand...

The MAWD's baro sensor is on the bottom of the board.

Sunlight shouldn't be able to reach it. You may want to look at your mount and make sure there is a little room under the MAWD.
 
Thanks for the input. The one thing our two rockets had in common were the hard landings. Although mine was a lot worse then his. I think I will build a test chamber to verify the altimeter is in complete working order before I fly it again. Or put it in a rocket and use motor ejection as a back up. Thanks for the help.

Dave
 
One problem with that logic; It's a little harder for that to happen as the MAWD has the Baro sensor on the back side of the board.


JD


jderimig said:
Sunlight on the baro sensor will cause very large fluctuations in the baro output. If you exceed the range of the device the PF might just report its maximum value.

If you use very small vent holes you will have created a pin-hole camera in addition to an av-bay. If the angles are right you can image the sun on your baro sensor. If the downloaded values shows wildly oscillating baro altitudes that is probably what happened.

A good practice with baro altimeters that use the ubiquitous MPX4115/6115 series is to make a small shade over the baro sensor with a small arc of masking tape (sticky side up).
Click to expand...
 
JDcluster said:
One problem with that logic; It's a little harder for that to happen as the MAWD has the Baro sensor on the back side of the board.


JD
Click to expand...

That was mentioned in an earlier post. Obviously I am not familiar with the MAWD. But other readers of this thread may have alts with the baro sensor facing the airframe wall and may learn something.....
 

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