Today's Message Index:
----------------------
1. 03:33 AM - Re: Digital Industrial Scales Outlets (juancax)
2. 05:01 AM - Re: Daily List Digest Question (dj45)
3. 07:31 AM - Re: alternator whine (Robert L. Nuckolls, III)
4. 10:07 AM - Re: Re: Dual batteries or dual alternators? (Robert L. Nuckolls, III)
5. 11:36 AM - Re: Re: Voltmeter & Ammeter normal ranges (Sebastien)
6. 04:06 PM - Re: Daily List Digest Question (David Lewis)
Message 1
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| Subject: | Re: Digital Industrial Scales Outlets |
Great post. thanks for sharing us. pornofavela.com (http://pornofavela.com/)
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| Subject: | Re: Daily List Digest Question |
I get one or two each week.
--------
Do not archive
Dan Stanton
N801S CH 801
N226BS CH701
N24DS CH750
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http://forums.matronics.com/viewtopic.php?p=473385#473385
Message 3
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| Subject: | Re: alternator whine |
At 08:37 PM 10/5/2017, you wrote:
>
>Hi Bob and others,
>
>My 182 has a noticeable alternator whine, about
>5kHz (I=99m guessing) at cruise rpm. I think
>it=99s worse recently than it used to be.
>
>Where and what should I start investigating?
Does operation of any audio panel selector
switch or setting of any radio or audio
system volume control have an effect on
the perceived noise?
Bob . . .
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| Subject: | Re: Dual batteries or dual alternators? |
Hello my friends, thanks for the answers.
Here I give more details so you can help me with my wiring...
I'm building an RV-7, it is in the final process, I have just hang
the engine, an Aerosport Power WildCat IO382; with full FlyEFII
ignition and injection system, and dual Ecus.
I consider batteries super confident, I have never had a battery
failure, but I have had an alternator failure 3 times in my life, 1
in the car and 2 in the aircraft... so I prefer 2 alternator, and one
odyssey battery.
Generally speaking, B&C alternators are
exceedingly long service lived. Failure
rates are a tiny fraction of the fielded
product. Most failures are due to installation
error or external influences.
A JUDICIOUSLY maintained battery is the
single most reliable source of electrical
energy in the airplane. A maintained battery
simply doesn't fail in flight. When maintained
batteries become unavailable in flight, it's
a result of effects external to the battery.
... may be later if I desire to make a very long flight, or a very
difficult flight like going to the Antartica, then I would consider
going there with 2 batteries and 2 alternators, but not know... first
I have to put this machine in the air...
With two alternators, the battery(ies)
are no longer tasked with alternator-out
endurance duties, hence they may be selected
primarily for their ability to crank the
engine and offer some stability to alternator
performance.
Said all this, I saw AeroElectric book and the Z-12 diagram. And I
already have all the components of that figure I bought everything in
B&C, including the stand by alternator for the vacuum pump (40 amps).
The pad mounted alternator is fabricated from
a 40A core . . . but if your pad is the
legacy gear ratio to the crankshaft, then
cruise rpm at the pad is on the order of 3700-
3800 rpm . . . too low to realize the machine's
full 40A output.
My question is if this diagram would work with my dual Ecu's EFII,
how would I need to modify this, does anybody have a picture of the
distribution of the components into the aircraft, and the switches in
the cockpit??
Is there a down-loadable installer's manual
for your engine? It's difficult, if not
foolish, to make recommendations without
knowing the requirements/recommendations
for all ship's electrical components, not
the least of which is your engine.
Bob . . .
Message 5
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| Subject: | Re: Voltmeter & Ammeter normal ranges |
Thank you Bob. Very good information and well presented. I'm looking
forward to learning more about the capabilities and limits of these
instruments.
On Thu, Oct 5, 2017 at 10:03 PM, Bob Verwey <bob.verwey@gmail.com> wrote:
> Absolutely facinating and insightful to a neophyte like myself <grin>
>
> On 05 Oct 2017 7:17 PM, "Robert L. Nuckolls, III" <
> nuckolls.bob@aeroelectric.com> wrote:
>
>> At 08:32 AM 9/24/2017, you wrote:
>>
>> Exactly. Joe could you please confirm that the jpeg below is visible? If
>> so it's obvious that while the voltage seems to be moving around a tiny
>> bit, it never gets to the point which would allow the amperage shown. It's
>> always above 14V. Also I checked some data with the engine shut down and
>> while the amperage still wanders around it's 1 A or less (-5.5 to -6.5 A)
>>
>>
>> Digital data acquisition is fraught with
>> opportunity for confusion/error. Depending
>> on how the variable is sampled, pre-filtered
>> and software filtered, data displayed or plotted
>> can take on the appearance of instability.
>>
>> Unless you're measuring the output from something
>> like a battery . . . or a laboratory power supply,
>> the stimulus being observed will have some noise
>> on it. This is especially true of signals gathered
>> from the DC power system of any vehicle.
>>
>> When I'm gathering data on relatively low frequency
>> events, my DAS pre-filtering is usually rolled
>> off at 10 Hz. Then interpretation software is
>> designed to do a 'rolling average' on sampled values.
>> For a DAS set up to gather 100 samples/second, we'll
>> buffer 16 samples in a memory stack, take the sum
>> of those values then divide by 16 for an average
>> of that 'packet' of data. When the next sample comes
>> in, we add the new value, throw away the oldest value
>> and do the average again.
>>
>> This pre/post processing of data does a nice job
>> of ignoring the high frequency perturbations that
>> are riding on top of the value of interest. The
>> processed data plots are nice smooth lines that
>> are more meaningful.
>>
>> I suspect that data plots taken from most
>> EIS systems have little pre-processing and no
>> post processing . . . so the traces are understandably
>> 'ragged'. So while the voltage traces might
>> be interpreted as 'unstable', it's probable
>> that the system is operating normally.
>>
>> Just for grins, I took the 'scope out to peek at
>> the 14v bus in Dr. Dee's '87 GMC Sierra. With
>> the 'scope set to 2.5S/div H and 2V/div V, we
>> get the following trace when cranking the engine.
>> [image: []]
>>
>> Figure 1.
>>
>> Note that battery voltage starts to sag from
>> about 12.8 volts but takes a steeper slope
>> as the starter contactor is energized followed
>> by a profound drop to 8 volts as the contactor
>> closes. A few milliseconds later, the voltage
>> rises to about 10v until the engine catches
>> approx 1.2S later and the alternator kicks
>> in . . . whereupon but bus rises to about
>> 14.6V
>>
>> [image: []]
>> Figure 2.
>>
>> In the next plot we see that the bus is 'steady'
>> at about 14.7V with the occasional perturbation
>> combined with some little 'spikes' with an amplitude
>> of 1 to 2 volts.
>>
>> To get a closer look at the voltage in the
>> next plot, we need to turn up the 'scope sensitivity
>> and to to AC coupling:
>>
>> [image: []]
>> Figure 3.
>>
>> With a vertical scale of 0.5V/div and horizontal
>> of 0.05S/div we can get a better look at the 'noise'.
>> This particular trace caught a 1.5v transient amongst
>> about 10 smaller artifacts.
>>
>> We see that even when there are no obvious
>> transients, the horizontal line has 'thickness'.
>> Zooming in closer:
>>
>> [image: []]
>> Figure 4.
>>
>> We find that the horizontal line is 'fuzzy' with
>> positive and negative going transients on the
>> order of 300mV peak.
>>
>> Depending on where your digital data acquistion
>> system takese a 'snapshot', the sampled votlage
>> might appear to 'wobble' by as much as +/-0.5V.
>>
>> Spreading out the major transients by a factor
>> of 20 . . .
>>
>>
>> [image: []]
>> Figure 5.
>>
>>
>> Shows that they're about 400 microSeconds wide. These
>> plots offer a small peek into the nature of DC power
>> systems on vehicles. A few weeks ago, a thread on
>> another list server offered this image suggesting
>> that the full-wave, rectified 3-phase alternator
>> would produce wave forms something along these lines . . .
>>
>> [image: []]
>>
>> Figure 6.
>>
>> Theoretically true, but I've never seen so 'clean'
>> a picture in the wild . . .
>>
>> Referring to Mil-Std-704 we learn that DC power systems
>> demonstrate a certain amount of noise (distortion)
>> under normal conditions. The document cites
>> the following plot for a 28v system (cut the
>> numbers in half for 14 volts).
>>
>> [image: []]
>>
>> Figure 7.
>>
>> Over the range of 1000 Hz (1 milliSecond period) and
>> 10,000 Hz (100 uSecond), we should expect artifacts
>> of noise up to 0.5 VRMS (1.5 volts pk-pk) on a 14V bus.
>>
>> Above and below those frequencies, the allowable/exoected
>> noise levels fall off. When you hook an oscilloscope to
>> the bus, the best you can do is sample small features
>> of the noise as illustrated in the first 5 figures. Further,
>> you'll never see the pristine plots hypothesized in Figure 6.
>>
>>
>>
>> [image: Emacs!]
>> Figure 8.
>>
>> The most significant attribute of a DC power system is VOLTAGE.
>> Referring again to Mil-STD-704 we find the plot above. Again,
>> cut the voltage levels in half for a 14v system.
>>
>> This figure suggests that any voltage vs. time condition
>> below the upper trace . . . and above the lower trace . . .
>> is a condition to be expected for designing and operating
>> appliances powered from the DC system.
>>
>> It's my wish that this narrative will give you some tools
>> for critical review of any data presented by either operating
>> or diagnostic instruments. Understanding characteristics
>> signals present on the bus -AND- limits on the measuring
>> instrument will go to better design, operation and diagnosis
>> of your ship's DC power system.
>>
>> Bob . . .
>>
>
Message 6
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| Subject: | Re: Daily List Digest Question |
There are a couple of anomalies noticed when receiving the digest version of the
list. One is the well understood and much discussed 'Emacs!' message in some
of Bob's posts. Regarding the 'pages and pages' of unreadable text, I believe
that may be associated with embedded images in a post that don't come through
in the digest compilation.
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