Today's Message Index:
----------------------
1. 02:37 AM - Re: Voltmeter & Ammeter normal ranges (andymeyer)
2. 04:09 AM - Re: Unsupported coax length (Bill Watson)
3. 05:38 AM - Re: Re: Voltmeter & Ammeter normal ranges (Sebastien)
4. 05:56 AM - Re: Voltmeter & Ammeter normal ranges (user9253)
5. 06:28 AM - Re: Voltmeter & Ammeter normal ranges (Charlie England)
6. 06:36 AM - Re: Re: Voltmeter & Ammeter normal ranges (Sebastien)
7. 06:59 AM - Re: Voltmeter & Ammeter normal ranges (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Voltmeter & Ammeter normal ranges |
Are your lines to/from the shunt twisted pair? If not, you may be getting loop
current from elsewhere in the system. Not sure how much, but worth a check.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473114#473114
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| Subject: | Re: Unsupported coax length |
No answers here, just what I did: I ran my RG400 through grommets but
also ran several other wires along with it. They were bound together
with the waxed thread stuff at roughly 12" to 18" intervals. It seems
to me that combining wires in a bundle provided a certain level of
support. I think some of the written guidelines suggest the same.
My guess is that RG400 alone thru grommets is just fine as well.
On 9/23/2017 8:58 PM, Paul Eckenroth wrote:
> Looking for advise on what the max acceptable unsupported horizontal
> length of RG400 coax might be. I have 23" between fuselage ribs and
> was planning on running the coax through a grommet in the tooling
> holes but then started questioning if this was good practice. So
> opinions are requested.
>
> Thanks
> Paul
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| Subject: | Re: Voltmeter & Ammeter normal ranges |
They aren't my lines but I'll check :). I'm also going through the install manual
for the 120 and looking for documentation on the alternator and voltage regulator.
Thanks for the idea Andy.
Sebastien
> On Sep 24, 2017, at 11:34, andymeyer <ameyer@mil-amax.com> wrote:
>
>
> Are your lines to/from the shunt twisted pair? If not, you may be getting loop
current from elsewhere in the system. Not sure how much, but worth a check.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=473114#473114
>
>
>
>
>
>
>
>
>
Message 4
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| Subject: | Re: Voltmeter & Ammeter normal ranges |
As long as system voltage is above 13, it is impossible for current to flow out
of the battery.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473122#473122
Message 5
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| Subject: | Re: Voltmeter & Ammeter normal ranges |
I did get the pic, but honestly didn't pay any attention to it. Just took a
look. Note that voltage never drops below 14V. So the charging system is
working great. My personal opinion is that you have too much of the wrong
information, and not enough needed information.
Where is the shunt wired into the system?
Is it really a shunt, or a hall effect sensor?
What does the current do with *all loads except the battery removed*?
(Yeah, I know you can't do that since the monitor is embedded in the EFIS.)
How about with everything turned off except the EFIS/monitor?
A typical shunt has, IIRC, a 50 millivolt full scale output to the meter.
Assuming it's a 60A shunt the output at the currents you're measuring would
be wandering around a few thousandths of a volt. That is a very small
signal, and as others have hinted, relatively easy to impress noise onto
the lines. And the most minute variations in resistance of any connection
anywhere in the sense circuit could cause large variations in voltage at
the meter.
I seriously doubt that there's anything wrong with the charging system.
There *may* be issues with the sensor and/or its wiring, but if it were my
plane, I'd almost feel like I was getting too much knowledge for my own
good. :-)
On Sat, Sep 23, 2017 at 11:14 PM, Sebastien <cluros@gmail.com> wrote:
> I'm guessing from some of the responses I'm getting that the picture I
> attached did not go through. The apparent current flow out of the battery
> is not from a high load. We're talking a 40-60 amp alternator powering 10
> amps worth of instruments and radios. The load cycles from -2 to +2 amps at
> least 50 times over the course of a 1 hour flight and it's not because
> someone's hiding under the floorboards flicking the lights on and off :).
>
> I'll try attaching the engine analyzer data again tomorrow. I did manage
> to check a few minutes of data from an identical analyzer in a different
> aircraft and while it did cycle up and down a bit, it never showed
> negative.
>
> Sebastien
>
> On Sep 24, 2017, at 04:50, ashleysc@broadstripe.net wrote:
>
> Hi Sebastien;
> Flow out of the battery is not abnormal and will happen whenever your
> aircraft consumes more power than its alternator can generate. It is not
> generally a signal to land immediately, but to reduce power consumption
> (like turn off the landing lights).
> Cheers! Stu.
>
> ------------------------------
> *From: *"Sebastien" <cluros@gmail.com>
> *To: *aeroelectric-list@matronics.com
> *Sent: *Saturday, September 23, 2017 4:09:48 PM
> *Subject: *AeroElectric-List: Voltmeter & Ammeter normal ranges
>
> I am doing the test flying on a friend's RV-6 and as part of the
> preparation I set up the engine monitor (Dynon 120) to display the
> following on the voltmeter and ammater:
>
> Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V
> Ammeter (wired to show current flow in to the batter): Red < 0A, Green 0 -
> 5A, Yellow 5-30A, Red > 30A.
>
> Battery is an Odyssey PC680 AGM. Alternator and regulator unknown, came
> with the kit from Van's 10-20 years ago. My guess is Plane Power.
>
> First Question: Do the ammeter settings seem reasonable? Obviously any
> discharge (<0A) is red as indicative of a problem that requires landing
> ASAP. Normal charge after a start has been observed to be < 5A within a
> minute after start, a hard start or low battery would obviously make this
> worse so I set green as 0-5A but don't have any good basis for this. Same
> for the yellow and red bands. I want the yellow band to indicate that a
> long time in this area is a problem, and red to be an immediate problem.
> Normally once the battery has been charged after a start the value should
> be zero so perhaps the green band should be 0-1A? What charge level going
> into this battery would indicate an immediate problem (red band)?
> \
> After first flight the low current alarm was constantly going off so I
> changed it from <0 to <1. Second flight had similar but not as frequent
> problem so I was going to lower it a little more but then I was able to
> download the engine monitor data to Savvy and WOW is it fantastic being
> able to look at graphs of engine data. I have no idea what normal would
> look like but here is a snap shot of the second flight:
>
> You can see the battery amps wander between -2 to +2, with excursions to
> -3 +3 later in the flight (during large engine power changes).
>
> Second Question: Is this behaviour indicative of:
>
> A. Normal operation
> B. Sensor problem
> C. Charging system or battery problem
> D. Something else
>
> Thank you all for your input.
>
>
Message 6
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| Subject: | Re: Voltmeter & Ammeter normal ranges |
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)
On Sun, Sep 24, 2017 at 5:54 AM, user9253 <fransew@gmail.com> wrote:
>
> As long as system voltage is above 13, it is impossible for current to
> flow out of the battery.
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=473122#473122
>
>
Message 7
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| Subject: | Re: Voltmeter & Ammeter normal ranges |
At 06:09 PM 9/23/2017, you wrote:
>I am doing the test flying on a friend's RV-6 and as part of the
>preparation I set up the engine monitor (Dynon 120) to display the
>following on the voltmeter and ammater:
>
>Voltmeter: Red below 10V, Yellow 10-13.8V, Green 13.8V-14.5V, Red > 14.5V
>Ammeter (wired to show current flow in to the batter): Red < 0A,
>Green 0 - 5A, Yellow 5-30A, Red > 30A.
Assuming you do monitor bus voltage and have
active notification of low voltage, then there
is no operational value for monitoring battery
current.
Battery ammeters in airplanes were a carry-over
from the terrestrial vehicles where the minus-zero-plus
instrument in the battery charge/discharge line
was the simplest single monitor of system health
during normal vehicle operations.
The ammeter would be expected to show a heavy
recharge rate right after cranking the engine . . .
or after a jumper cable start on a dead battery.
After some interval of normal operation, the battery
accepts less and less recharge energy and the needle
migrates toward zero. Under normal ops (votlage about
right, battery charged) the needle would rest at or
just slightly above zero.
If generator output was insufficient (low engine rpm,
high system loads, regulator voltage drifting downward,
generator failing) the needle would present some
value below zero.
While truly an analog instrument, its BEHAVIOR was
closer to 'digital' in that it was never intended to
be READ so much as observed as a go/no-go panel
instrument.
Ammeters of all types are of little to no value as sources of
operational data in flight. Ammeters in the battery
lead are pretty much useless when compared to an accurate
voltmeter paired with active notification of low
voltage.
Calibrating a battery ammeter with alarm settings
will be an exercise in futility.
Suggest you move the ammeter sensor to the alternator
b-lead and eliminate any alarm functions from this
reading. The ammeter is most useful as a maintenance
tool for diagnosing why the VOLTAGE is low and/or
the LOW VOLTS warning light was illuminated in the
air.
Bob . . .
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