I have to log 150 discrete inputs, some AC and others DC, voltages and
currents. I plan on using simple inductive pickups and voltage probe
points. The problem is, that I need to log the levels over varying
conditions using a laptop and some sort of interface and over a couple
hours . The testing will take place in an aircraft, both pressurized
and non pressurized up to 30k feet. Any suggestions?
I know I'll need a DAC, just not sure which would work best. I also
figured I could use either a serial or parallel port interface with
How often do you need to log each input? Do some inputs need to be
logged more often than others? What kind of voltage and current ranges
do you need? Do you need analog measurements for everything, or is
digital OK for some of the inputs? How accurate does each analog reading
need to be?
The 150 channel requirement is a biggie. If you don't need to log each
input that often, it's not as big of a deal, but if you need high data
rates, it may get a little expensive.
Budget? If you have plenty of somebody else's money, and you don't need
to log each channel more than once every several seconds, go buy a data
logger like a Fluke Hydra. This is essentially a good auto-ranging
multimeter with a DP21T switch on the input leads. Some models can only
output the data immediately over a serial port, while some can store data
in an internal memory. The potential problem here is that it costs
US$2,000-$3,000 for 20 channels, and you need to do that seven and a
half times. You might be able to buy one data logger and multiplex the
inputs to it with external silicon, switches, or relays. You need a
40P8T contact arrangement...
Instead of trying to log everything at once on a laptop, it might work
better to select smaller boards with 10 or 20 inputs and let each board
log to local memory, then download all the boards at the end of the
flight. This may also tend to reduce the number of wires strung around
the aircraft, if you can locate the boards near the measurement points.
You need some kind of sync between the boards... they all have to start
their clocks at the same time, or get individually synchronized to GPS
or WWV, or you need to string a wire between them. You may also have to
be careful where you put the boards physically... if they make the
aircraft radios go screwy the pilot will not be happy with you.
This may be obvious, but it's probably a bad idea for there to be just
one person trying to fly the plane and operate the data logging at the
same time. If one-man operation is required, the interface to the data
logging has to be very simple, or even something that can be started
before takeoff by someone else and stopped after landing.
I'm somewhat curious as to what you're doing... most of the people that
want to do something like this probably work for an aircraft
manufacturer and in that case I would think they'd just buy
off-the-shelf stuff. But hey, maybe you're building an experimental
jet in your garage. :)
Once you can answer most of the questions above - in other words, when
you can state your requirements more clearly - you may want to
cross-post or post to sci.electronics.design for more good input.
On Sat, 04 Jun 2005 05:33:19 GMT, in alt.engineering.electrical you
Still to be determined, but preliminary data acquisition will need to
be during major changes in flight profiles, such that sample rates may
only be required when user selects the need and not a continuous
No, in fact would rather have all samples at the same time for
Gen output is 40kVA three total & One 1kVA
115v 1 phase 400Hz 650 amps
115v 3phase 400 Hz
220v 2Phase 400Hz
28 vDC 200 amps max. There are two TRs tied together in parallel, EA
max 100 amps. Loss of various equipment will be executed and data
sampled for future capabilities and emergency procedures. The main
concern is the capability of the TRs to handle various loading
configurations but data for all sources is required.
Data will be used for reporting purposes, future calculations and
modeling. I will probably end up building a more accurate model then
currently exists (current model is solely analytical, no hard data
available) All the sources are analog, but how those samples are
obtained, I don't think will make a difference. I thought simple
inductive pickups that feed analog to dig conv for recording.
Big question! I would want at most _+2%. I suspect any more
deviation may make modeling too inaccurate.
I'm simply recording all the aircraaft electrical loading during
various phases of flight
LOL yea right. in house resources avalablity of equipment., Next
week I can check whats avalable, for now, I'm simply attempting to get
a solid foundation for a POA.
I do have GPS signals available
I have a crew on board, flight crew, trechnicians, engineers (me) 707
I wish LOL no.... DOD trying to avoid using $$$$$ contractors, We
have the resources, but money is limited and this is my 1st project of
this magnitude that I'm heading up.
product(s) from here may be what you are looking for
also http://www.microdaq.com /
for a short term project where you have no use for the test gear after the
project is over i'd call one of the rental outfits to see what thay have.
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