Basic specs
Range: sea level to 1000 meters (1000 to 2000 meters with hardware mod)
Resolution: +/- 1 meter
Data storage: Variable sampling rate allows 3.5 to 170 minutes of data per flight
Data format: RS-232, 19200 baud
Power: “Altimax-4.8” 3 - 5.5V input range, LiPo battery optimum, 10mA current
“Altimax-6.0” 5.5 -7V input range, 5 cell battery, 5mA current
Standard battery: 60mAh Lithium Polymer, 6 hours operation, 2.1 grams w connector
Altimax weight: 2.7 grams, 4.8 grams total with battery
Altimax dimensions: 40 x 15 x 5mm
Palm Pilot
Software files
Analysis.prc
Mathlib.prc
NSBRuntime.prc
NSBSystemsLib.prc
Palm Pilot
Setup
Palm unit must have a serial
port and run Palm OS 3.5 or later. All the files above should be installed by
Hot Sync to a PC or by beaming from another Palm. Run “Altitude Analysis”
and by tapping on the top menu go to Tools, then Options. Under Logger version,
select “Altimax” and tap OK.
Setting the
Sampling Rate
A new feature of the Altimax
allows the user to set the sampling rate to achieve the best compromise between many data points each second for highly detailed
data over a shorter time, or fewer data points per second with a longer flight time.
The default “fast” sampling rate is 5 measurements per second which gives about 3.5 minutes total time,
or a “medium” rate of twice per second can be used for about 8.5 minutes of time, or a “slow” rate
of once per second will give about 17 minutes. Another option will sample once
every 10 seconds for 170 minutes for any application that the mind can dream up.
Because detailed data is
most valuable at the very beginning of the flight during the typical fast climb after launch, the Altimax is designed so that
the initial 20 seconds of data is fixed at the fast rate. This is split into
10 seconds of “buffer” before the launch trigger, and the first 10 seconds of the initial flight after the launch
trigger. The variable rate is effective for the remaining flight after this first
20 seconds. If the “fast” rate is chosen then the rate will be a
constant 5/sec for the entire flight and this is the default and recommended mode. If
any of the slower rates are chosen, then the rate will change at the 20 second point accordingly.
The sampling rate is set
by plugging the Altimax into the Palm Pilot and running the Analysis program. Go
to the “Altimax” menu at the top of the screen and then press “configure”. Tap the “Set sampling rate” button and press the Altimax button to reset or power it up. A box will then show up after a few seconds showing the choice of sampling rates. Tap the correct box and then tap “Set”.
This setting will be retained indefinitely until changed again.
Setting Trigger
Level
With Altimax plugged into
the Palm and with Analysis running, go to the “Altimax” menu at the top of the screen and tap “configure”. Now tap the “Set threshold” button and when the screen says “Power
Up Altimax” press the Altimax button and wait while communication is established.
After a few seconds the old threshold will be displayed. Enter a new value
by writing over the old value using digits from 1 to 99 and tap the “Set” button.
This number represents the trigger altitude in meters and will stay in memory indefinitely, even with no power to the
unit, until changed again.
Recording
Flight Data
Altimax powers up as soon
as the battery is plugged in. With the unit installed in the model, press the
button once with the model near the ground and hold the model for a few seconds. The
Altimax LED will blink 3 times and then the unit will make an initial pressure measurement which will be used as the zero
altitude ground reference for the following flight. Altimax then continuously
measures the altitude and compares it to a preset “trigger” altitude, such as 55 meters for F1A (or perhaps 10
meters for other models). When the trigger altitude is reached Altimax will begin
to record data into memory for the next 3.5 minutes. Any data from previous flights
will be overwritten. When finished the LED will blink twice and the unit will
shutdown to a low power state to save the battery and the LED will blink once each second, alerting the user that the memory
is full of new data. Although not normally visible during flight, the LED also
signals status by blinking once when the trigger is reached, and by blinking faintly at a rapid rate when recording data after
the initial 20 seconds. Also note that Altimax records data 10 seconds prior
to the moment of the trigger. This allows for analysis of the setup prior to
the launch in the case of F1A, or will give a few seconds on the ground prior to launch for other models.
Dumping Data
to Palm
With the cable adaptor connected
to the Palm serial port, push the 2.5mm connector into the Altimax data jack. Run
Altitude Analysis and tap the “Read Altimax” box. After the program
says “Waiting for logger to send data”, press the button on Altimax. The
program will then indicate it is receiving data. After receiving the data points,
which may take 15 or 20 seconds, the program is ready to save or plot the data. Altimax
can be unplugged and turned off.
Erasing Altimax
It is not necessary to erase
the flight data in the Altimax as a new flight will automatically write over the old flight.
However if the new flight is shorter than the old flight some of the old flight data may appear right after the new
flight which can be confusing. To avoid this there is an “Erase”
button in the software that can be used if desired. Tap the button, power up
the Altimax and wait. The LED will glow faintly during the erase process and
will flash twice when it is done.
Analyzing
Data
It is good practice, although
not necessary, to save the flight data immediately following the dump. A default
file name including the date and time is automatically generated along the top of the screen.
This can be edited if desired to add the model name and the data is saved in the Palm when the “Save” button
is tapped. Note that this process, like dumping and plotting, is very slow on
older Palms sometimes taking 15 or 20 seconds. Thousands of flights can be saved
in a Palm for study and later reference as long as the Palm battery never dies!
After the dump or saving,
tap the “Plot” button to view the flight data. After some time calculating,
an altitude vs. time plot is displayed. Small sections of the flight can be viewed
in more detail by tapping the “Zoom X” button and then inputting start and end times to define the section to
be viewed, and then tapping OK. In a similar fashion tapping the “Slope”
button will allow for the average slope of the plot over any time window to be calculated which is very useful for climb speed
or glide sink rate comparisons. A newer feature will give an estimate of the
sink rate at any point of the flight by simply tapping on the line of the data. It
will also make a projected estimate of the total flight time to the ground based on the current altitude and assuming a constant
sink rate for the remaining flight.
The variable sampling rate
makes the plotting of the data more complicated because the plotting program can only handle a fixed rate for any one file. To deal with a variable rate flight the software must either fill in new data points
between the slow points so that the entire file works like it was done at the fast rate, or it must reduce the data points
for the first 20 seconds so that the entire file looks like it was done at the slow rate.
Since the number of data points has a big effect on the speed that the Palm Pilot can plot the data, this problem is
dealt with by allowing the user to choose either “slow” or “fast” plotting speeds. When a variable rate data set is loaded there is a box at the bottom of the screen for “Fast plotting”,
and it also indicates the rate of the file which is loaded. If the “Fast
plotting” box is checked then data from the first 20 seconds will be minimized to make for the most efficient and quick
plot. If the box is not checked then the extra data points will be added which
will make the plot processes slower, but none of the initial 20 seconds of data will be lost.
“Fast” and “slow” can become confusing here because a fast data rate makes for slow plotting
and vice-versa. Note also that for a normal data set that is completely fast
rate, the only option is slow plotting.
To speed up the plotting
process when only a small amount of data needs to be analyzed, for example if the initial launch altitude is the only data
of interest, then the data download size can be limited to keep the data set small.
To do this go to the “Tools” menu, select “Options” and under “Altimax download size”
enter a smaller number such as 200 units. Each unit corresponds to one measurement,
so at the fast rate 200 units would be 40 seconds. The maximum size is 1125 units.
Note that the
Altitude Analysis software is written by Petri Kuikka and Tapio Linkosalo. More details are available on their website: http://koti.welho.com/pkuikka/aa/.
This is a “giftware” program, and for every Altimax unit purchased a donation will be automatically
made to Tapio and Petri to support their work. Any additional donations and suggestions
for this program would be welcome.
