Perfect Flight SL 100 Altimeter

[Getmore]

If I go with two alt. can I make a y harness so one switch will turn both alt. on?

[gdiscenza]

If I go with two alt. can I make a y harness so one switch will turn both alt. on?

You could, but that commits both altimeters to a single point of failure. If you are designing for redundancy, go redundant. Two switches, two (or more) batteries, two altimeters, and two ematches/ejection charges per event.

G.D.

[Getmore]

Well put, Thanks

[cerving]

Another good thing about this altimeter is its durability. This is a robust little unit. My Stratologger has been in a crash (main failed to deploy) and 2 shreds. Takes a licking and keeps on ticking. With a 9V battery, it ignites e-matches almost instantaneously.

The only issue I know of is that its recording of speed past mach 1 is suspect. Don't have to worry about mach delay, but when it records that your rocket hit 6,000 MPH on a J motor, you have to raise an eyebrow.

Definitely get the download setup.

The spurious velocity reading is because the air pressure buildup past Mach 1 makes the air pressure drop, so it "looks" like the rocket has lost altitude. Altimeters that look for this phenomena (like the Stratologger) know that if the perceived altitude suddenly has a large drop and the rocket was moving at a good clip previously (say, over 700 ft/sec) then it's almost certainly due to near-mach pressure buildup, so they hold off any deployments until the altitude starts to rise again, meaning that the rocket has come out of mach. Unfortunately, since this pressure buildup is going to peak sometime during the motor burn period (most likely right before burnout) any altimeter-only flight computer isn't going to be able to give you an accurate maximum velocity reading near mach speeds. That pressure-altitude difference times the samples/second rate is your velocity during that interval, so any error gets magnified by a factor of 20 or so. You'll need a unit with an accelerometer if you need an accurate near- or post-mach velocity reading. If you can live without this data then a unit like the Stratologger is a good buy for the money.

[DRAGON64]

You could, but that commits both altimeters to a single point of failure. If you are designing for redundancy, go redundant. Two switches, two (or more) batteries, two altimeters, and two ematches/ejection charges per event.

Exactly, redundancy throughout... two seperate systems making sure you recovery safely.

[cwbullet]

Exactly, redundancy throughout... two seperate systems making sure you recovery safely.

I actually think that if you going after redundance, you should make it truly redundant. Redundancy means there should not be a single point of failure. Well except one parachute and recovery harness.

[cavecentral]

I actually think that if you going after redundance, you should make it truly redundant. Redundancy means there should not be a single point of failure. Well except one parachute and recovery harness.

Drag races are truely redundant :-)

[Getmore]

^^^^

[Rocketjunkie]

I actually think that if you going after redundance, you should make it truly redundant. Redundancy means there should not be a single point of failure. Well except one parachute and recovery harness.

This is where failure occurs far more often than an altimeter failure.

[cwbullet]

I would agree. Most of my failures as well as the ones I have witnessed have been due to the parachute and harness not being fully deployed for what ever reason. Very few are due to the electronics. I usually have 2 charges on both compartment. The first charge is t the level I ground test to be the minimum charge to cause a successful separation and the second is a little larger to ensure it separates. On my level 3, I used 6 and 8 gms.

I hate when the chute gets stuck in the tube.

[Getmore]

Ah chuck that brings a good thought to my head. I am going to test the charge by the amount of powder used in the 54/852 forward closure. I have a scale for reloading that will tell me how many gms that amount is and add a little more for the main deployment. I like playing with the Black stuff

[cwbullet]

I agree. I love ground testing. My neighbors do not and that is why I given them a heads up.

[Getmore]

Ya the neighbors can slow things down a little. But here at my shop is in a industrial area no worrys on the weekend anyway.

[cwbullet]

I have several neighbors that willing the blue lights around if you don't ask first.

[DRAGON64]

I just ordered three of these altimeters. These will be dedicated to two different rockets; one 4" rocket will get two, and a .26" rocket will get one etc. The idea is, that when I build another rocket, I will order another altimeter for it etc.

[Getmore]

I should be getting mine saturday or monday.