ARTS and ARTS2

Eric

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So I picked up so Ozark Aerospace items, and I finally got to fly them. I used the ARTS as primary and ARTS2 as back-up. They worked great and I got some great data out of them.

But I have one question. Why does the accelerometer altitude differ so much from the barometric alt? The baro alt is what I had simmed the flight at. But the acc alt is almost double.


0204181418.jpg 0204181416.jpg 0204181432.jpg 0204181442.jpg
 

tHoagland

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Can't help with the question but for future reference, the "ALT" key + "PRT SCN" key will copy the current window to the clipboard which can be pasted into a blank Paint file. This would provide better images for people to look at and lead to better answers.
 

markkoelsch

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The accelerometer might be measuring distance traveled to apogee- not altitude. Did it weathercock?


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ksaves2

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The Arts 2 'was a very nice unit and even had an egg finder type GPS to go along with it. I picked up a GPS to go along with my Arts 2 and for folks who had the money in 2007 it was the cat's meow. Kurt
 

manixFan

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Accelerometers are notoriously poor for altitude measurements as they integrate motion to determine distance. Any errors accumulate over time and if you have weathercocking or other issues they also confuse the true reading. Even worse it’s possible that even after deployment they can still experience positive G’s and think they are still gaining altitude. A payload bay spinning under a drogue for example.

I would not even bother with the accelerometer altitude since the barometric will be so much more accurate. This is true pretty much regardless of brand of altimeter that offers both measurements.

I like the ARTS 2 and use one on some my larger rockets.


Tony
 

Eric

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Thanks for the replies. I do have the ARTS GPS that has an ARTS on top of it. But it is a little big for my rocket avbay. I probably won't use it since I went the eggfinder route. I might just put that whole system in the yard sale section.

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Larry Curcio

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So I picked up so Ozark Aerospace items, and I finally got to fly them. I used the ARTS as primary and ARTS2 as back-up. They worked great and I got some great data out of them.

But I have one question. Why does the accelerometer altitude differ so much from the barometric alt? The baro alt is what I had simmed the flight at. But the acc alt is almost double.


View attachment 337802 View attachment 337801 View attachment 337800 View attachment 337799

Three questions:

1) Did you launch vertically?

2) Was the rocket stable during ascent

3) What was the temperature?
 

Eric

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Three questions:

1) Did you launch vertically?

2) Was the rocket stable during ascent

3) What was the temperature?

1, The launch rail was with in a degree or two of vertical.

2, It went strait up, and leaned over at the very top.

3, Started the day at 60*. Might have got up to 70* . Calm 2-3 mph winds.
 

Larry Curcio

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1, The launch rail was with in a degree or two of vertical.

2, It went strait up, and leaned over at the very top.

3, Started the day at 60*. Might have got up to 70* . Calm 2-3 mph winds.

Then it looks all bent outa shape :smile:
 

Larry Curcio

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What looks bent out of shape?

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The data is (are) all bent outa shape. Calibration? (The ARTS units are self-calibrating.) Wrong orientation? (Self-calibration gives you a lot of latitude there. Dobut it.)

Are the barometric data credible?

-Larry (Out of practice in this realm) C.
 

Eric

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I would think both units being out of calibration at the same time would be odd. Because they both gave the same kind of altitude curve. The barometric altitude is what I had simulated. So I believe it. Both the ARTS and the ARTS2 are oriented in the correct direction.

This is my first time flying an altimeter with an accelerometer. 0202180753.jpg 0202180752.jpg 0130181714.jpg

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manixFan

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Eric - I don't think any of the accelerometer based altimeters do a good job of recording altitude. They are not very reliable at detecting apogee for the same reasons they don't calculate altitude correctly. Your plots look very similar to the ones I've gotten not only from my ARTS, but whenever I've tried plotting accelerometer based altitude. Almost universally they greatly over estimate the altitude.

For deployment events and altitude, barometers are hard to beat. But I like knowing what else goes on during the flight, like motor burn duration, stress caused by ejection charges, pieces bumping into each other, etc. Accelerometers are great for that additional kind of info.


Tony
 

Larry Curcio

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I would think both units being out of calibration at the same time would be odd. Because they both gave the same kind of altitude curve. The barometric altitude is what I had simulated. So I believe it. Both the ARTS and the ARTS2 are oriented in the correct direction.

This is my first time flying an altimeter with an accelerometer. View attachment 337993 View attachment 337994 View attachment 337995

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It looks almost like 1 g isn't being subtracted from the acc data. Something is horribly wrong. Can you post the exported data (i.e.; not just the graphs.)
 

5x7

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You can read the sensors when connected to the Data anylizer in diagnostic mode. What does the accelerometer read? (orient the arts in launch direction).
 

UhClem

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There are two calibration factors for the acceleration.

The 1G value which is subtracted from all readings during flight is calculated each flight prior to launch.

The sensitivity (ADC counts per 1G) is calculated using the GUI (so the manual says) and stored in the altimeter.

One of these is out of whack. You can't do anything about the 1G offset but you can recalibrate the altimeter. Correcting existing flight data may or may not be possible.
 
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