Re: major electronics analysis project help needed TIA
- From: "Don Baker" <n2mcg@xxxxxxxxxxx>
- Date: Sat, 4 Jun 2005 09:37:51 -0400
I did a similar data acquisition system for the 757 about 3 years ago. If
you email directly with a good email return address then I will gladly share
my experiences and the approach we used.
Don
"JB2" <none@xxxxxxxx> wrote in message
news:le93a1p01c4r25epbepqtgba3ipln94uvc@xxxxxxxxxx
> On Sat, 04 Jun 2005 05:33:19 GMT, in alt.engineering.electrical you
> wrote:
>
> >JB2 <none@xxxxxxxx> wrote:
> >>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.
> >
> >How often do you need to log each input?
> 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
> sampling.
>
> > Do some inputs need to be logged more often than others?
> No, in fact would rather have all samples at the same time for
> comparative analysis.
>
> >What kind of voltage and current ranges do you need?
> 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.
>
> > Do you need analog measurements for everything, or is
> >digital OK for some of the inputs?
> 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.
>
>
> >How accurate does each analog reading need to be?
> Big question! I would want at most _+2%. I suspect any more
> deviation may make modeling too inaccurate.
>
> >
> >>Any suggestions?
> >
> >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.
> >
> >>I know I'll need a DAC, just not sure which would work best.
> >
> >Budget?
> 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.
>
> > 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...
> Outstanding suggestion
> >
> >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.
> I do have GPS signals available
> >
> >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 have a crew on board, flight crew, trechnicians, engineers (me) 707
> A/C
>
>
> >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. :)
> 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.
>
> >
> >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.
> >
> >Matt Roberds
> thanks Matt
.
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