Altimeter 2 problems

[ascastil]

So I've used this only twice and both times it didn't really log anything, or at least I can tell the data is incorrect. The first time I thought I needed a vent hole, so I drilled one (this was probably a year ago haha, haven't used it again till today). Now today with different rocket and vent hole, from what I can remember last year, very similar readings.

Altitude 2 ft
Ejection 2ft
Flight duration .4sec
Top speed 54k
Peak acceleration 40g
Coast to apogee 0sec
Flight descent 0sec
Battery level 93%
Thrust time .4sec

I'm turning it on and holding and releasing when it says launch and then ready. Am I doing something wrong? It should have been a couple thousand feet at least, not 2ft. It did sit on the pad for 7min while I got GPS tracker ready.

 

[BEC]

Did you drop it onto the pad hard enough to fool the A2 into thinking it had been launched? Or drop it on the way to the pad?

AltimeterTwo (and Three) use the the accelerometer aboard for launch detection.

 

[ascastil]

No I did not. I did open the rocket back up to verify I had the chute release turned on and saw that the altimeter was also still on. Then I just picked the rocket off my table, walked to pad, and slid it onto the rail. Wasnt dropped or anything. Thanks for the response also.

Would even dropping it give me a 40g acceleration and 54k top speed though? That's a hell of a drop haha.

 

[BEC]

Yeah, that would be a bit of a drop. So I figured it was a long shot. But I can't think of anything else. The Chute Release worked OK?

I understand the need to check to see that the CR is on....been there, done that.....

 

[ascastil]

I did read over the instructions again and it does say jostling it will make it think it launched and give weird readings like you said. I really dont think I moved it around a lot. Wonder how much movement is too much.

I also only have one 1/8th inch (I think) vent hole on a 2.5 inch BT. Do I need more? Chute release works...

 

[BEC]

It takes a pretty good jolt I think. I am trying to remember if I've ever false-triggered an AltimteterTwo or Three by mishandling the model. Nothing comes to mind, unfortunately.

 

[John Beans]

Yep, BEC's got the right idea; when you see a crazy low altitude, that indicates a "false launch." The rest of the data will be nonsense.

AltimeterTwo uses its accelerometer to detect launch, so the only thing venting would affect would be altitudes.

AltimeterTwo tries to ignore the accelerations of normal handling and loading onto the pad, but it's not perfect and it has to be able to detect very short impulse motors (it detects thrust times as low as 0.2s).

Just be aware of how it triggers, and if possible take a peak to make sure it says Ready right before you gently close it up, ideally before you drop it down a rod or rail. If you do, slide it gently and avoid a drop at the end.

Some people never see false launches. Some people's habits and movements are just right (wrong?) in some magically appropriate way to see them more often.

Hope that helps?

 

[mikec]

It takes a pretty good jolt I think. I am trying to remember if I've ever false-triggered an AltimteterTwo...

I've triggered mine with what I thought was very light handling many times. I've got pretty early firmware, I don't know if John has adjusted this in later versions.

 

[John Beans]

At the risk of boring everyone, or seeming to wiggle out of the responsibility for how AltimeterTwo performs from time to time, I would say this.

The real value of any altimeter—even simple ones like AltimeterOne—is in software and how it thoughtfully filters the sensor data. Seems like you could just take a sensor and read values, but rocketry is a very chaotic environment, and it takes plenty of interpretation to make sense of what you read.

The challenge is magnified when you layer on all of the rocketry flight analyses that AltimeterTwo performs—without a computer.

For instance, there can be trade-offs between careful, immediate detection of both launch and burnout, while still making the altimeter easy and convenient to use. The more sophisticated you try to be with things such as the direction of acceleration/deceleration (remember, AltimeterTwo has a 3D sensor, but there are no requirements for orientation or mounting), or using the pressure sensor around launch time, the more open you leave yourself to little exceptions that are hard to anticipate.

The algos have been tweaked slightly over time. The latest AltimeterTwo firmware is version 4.04 on the latest hardware (which has also evolved slightly over time). If your AltimeterTwo is working well for you, no need to update. If you're having some frustration, just send it in and we'd be happy to flash it with the latest firmware we have available for your hardware, no charge.

 

[ascastil]

So out of curiosity just now I turned on the altimeter and held it in my hand and acted like I picked up rocket from a table and did the motions like walking toward the pad and loading it up. I got it to activate with some arm swings like when your walking. Maybe thats whats doing it. I couldnt get it to do it when I acted like I was moving the rocket up onto the pad. Maybe I found my mistake. Thanks.

John, I saw that my hardware is version 4.0, is it even something to be concerned with? Maybe I can fix it with just gentle handling.

 

[Nytrunner]

These days I just turn mine on at the pad (usually arming the chute release at the same time).
It's a habit that carries over from arming high-power electronics

I got a stupid reading from the Alt 2 one time early on, and it was probably from rocket handling on the way to the pad as mentioned above