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Analysis: Best value logging altimeters

Discussion about deployment systems including altimeters, timers, air speed flaps, servo systems, and chemical reactions.
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anachronist
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Analysis: Best value logging altimeters

Post by anachronist » Wed May 24, 2017 9:41 pm

(updated 12 July 2017)
I imported the list at http://rocketsetc.com/altimeter-comparison/ into Excel and set up some data filters to find a logging altimeter (NOT peak altimeter) with a PC interface for downloading flight data. Prices don't include the price of external batteries or chargers, but the weight quoted does include estimates for batteries. Add $10 to the price as an estimate of the cost to include an external battery.

Non-deployment logging altimeters

These are the affordable logging altimeters I found that have no recovery system deployment capability, just recording altitude only.

HobbyKing logging altimeter: 19g (est with battery), $29 w/o battery.
This isn't included on the list linked above. This altimeter is a re-labeled version of the FlyDream altimeter, very light weight (less than 2 grams excluding battery), relatively slow recording rate up to 8 samples per second, goes up to 900 meters, or about 3000 feet, which is fine for even class A water rockets. The problem is, it needs a software driver to be useful, and it doesn't seem to be supported past Windows XP. The fd-rc.com site has some drivers that should work, and the hobbyking.com site has some user-supplied drivers. If you can get it to work, this is the lowest price I can find.

TinyCircuits Rocket Alimeter Logger: 8g-9g (incl battery), $69 for all parts.
This is a very small and lightweight kit that requires no soldering. Just purchase 4 tiny circuit boards having different functions (USB, processor, barometric sensor, SD memory) plus a battery, hook them up, load in the software, and you're done. The device logs both altitude and temperature, although I don't know the data rate. It looks simple enough to program, and you can modify the source code yourself. This looks great for a tinkerer.

PerfectFlite Pnut: 7g (battery included), $72.
This altimeter is TARC-approved for pyro competitions; not relevant to water rockets but good to know. It has a nice low launch detect of 40 feet, great for water rockets, and super light weight. The $72 cost includes the data transfer kit, which you have to buy in addition to the altimeter. Without the data transfer kit, you can just get altitude beeped at you after each flight. The point here is to log the flight, so you need the data transfer kit.

Altus Metrum MicroPeak: 2g (battery included), $80.
This altimeter is also TARC approved for pyro competitions. The advertised price is $30, but it really costs $80 because you have to invest in an optical USB transfer adapter to get data off the device. The advantage to this altimeter is that it weighs less than 2 grams with battery! One potential problem is the high launch detection height of 30 meters (100 feet). There's a "water rocket" version of this, the MicroSplash altimeter, having a launch detect height of 10 meters (33 feet). It costs more, though, bringing your total cost to $98 with the optical USB transfer adapter.

Jolly Logic Altimeter Three: 11g (battery included), $100.
If you're going to spend $100 on a logging altimeter without deployment, this is the one to get. It's light weight and has wireless data transfer capability to your mobile device, which is really cool. If you can tolerate 3 times the weight, though, I'd go with the Eggtimer Quantum (below), which also has wireless data transfer, deployment capability, and direct servo control.

Deployment logging altimeters

These are the most affordable logging altimeters I found that include a parachute deployment capability. Mostly, this involves the device outputting a current from two terminals to burn a pyrotechnic squib. You would have to find some way to use this for water rockets, such as controlling a solenoid to pull a latch, driving a small motor as a winch to pull a latch, or signaling a servo controller to drive a servo. The Eggtimer altimeters can be configured to drive a servo directly. None of these altimeters includes a built-in battery.

Eggtimer: 28g (including LiPo battery), $40 (incl USB cable)
This is Eggtimer's original deployment altimeter, with many configuration options. You can use just about any battery (even coin batteries for short periods). You need to hook it up via USB to a terminal program to program it, but it seems pretty straightforward if you follow instructions. Launch detection can be set as low as 50 feet, samples/second can be as high as 33/sec for ascent and between 1-10/sec on descent. You can configure it to drive a servo instead of pyro squibs, and you have two different deploy times you can set.

All Eggtimers are kits, though. You will need a 15-watt soldering iron and some patience to solder surface-mount components, but there aren't a lot of components and the instructions are detailed.

Eggtimer Quantum: 34g (est with battery), $45 (incl USB cable)
This is a WiFi-capable altimeter. As such, it needs 7.4V (a 2-cell LiPo battery), which weighs about 17g added to the 17g of the altimeter. The $5 USB cable is required to update the firmware if needed. Otherwise, you program it via a browser on any device over the WiFi connection supplied by the altimeter. Really cool! I'd definitely get the Quantum if the weight is acceptable - not only is it more convenient to download data, but it's configurable through any browser. Communicating with the device over WiFi is a huge value for the price. AND, like the regular Eggtimer, you can use it to drive a servo directly. Servos are available as light as 4 grams.

I'd say this is the best overall altimeter for water rocketry in terms of price and capability -- if you can tolerate the weight. Again, this is a kit that you must build yourself.

Adrel ALT-BMP: 8g (est with battery), $63 (w/o battery).
Good information on the website, looks perfect for water rocketry. But nobody is selling it! Their website refers you to another website that doesn't list the altimeter in their catalog. So we'll scratch that one. If it were available, this might be a good choice.

PerfectFlite StratoLoggerCF: 28g (est with battery), $72 (with USB data transfer kit).
This is about the same size as the Eggtimers but a bit lighter. It records a straight 20 samples/sec and includes two deploy signals, with the main parachute programmable to deploy as low as 100 feet. Its launch detect is 160 feet though.

Altus Metrum EasyMini: 24g (est with battery), $80 (w/o battery).
This altimeter is only 7g without battery, and has the USB connector built in. You can use any battery between 4 and 12 volts; a 2S 300mah LiPo is about 17g. It automatically logs 100 samples/second on ascent and 10 samples/second on descent. It can record 10 minutes of flight, plenty for our purposes.

The next higher price point is around $100, where we have the MissileWorks RRC3 Sport (34g with external LiPo battery) and Entacore ISM USB (25g w/ LiPo battery). They have similar capabilities to those listed, but at a higher price.



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anachronist
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Re: Analysis: Best value logging altimeters

Post by anachronist » Tue Jun 06, 2017 3:40 pm

12 July 2017 - I have updated my post with new information and organized it by non-deploy and deploy-type altimeters, ordered by price.



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