Today's Message Index:
----------------------
1. 02:00 AM - Re: Re: Thermocouple leads (James Kilford)
2. 05:01 AM - Re: Can Xfeed damage smaller battery. (bobbarrow)
3. 06:53 AM - Re: Re: Can Xfeed damage smaller battery. (Robert L. Nuckolls, III)
4. 01:29 PM - WTB dead Narco CP 135/136 or similar (John Loram)
5. 04:32 PM - Re: Re: Thermocouple leads (David)
6. 04:35 PM - Re: Re: Thermocouple leads (David)
7. 05:40 PM - Re: Re: Thermocouple leads (Robert L. Nuckolls, III)
8. 07:48 PM - Re: Re: Thermocouple leads (Paul Millner)
9. 07:48 PM - Re: Re: Thermocouple leads (Paul Millner)
10. 08:04 PM - Re: Re: Thermocouple leads (David)
11. 08:04 PM - Re: Re: Thermocouple leads (David)
12. 08:24 PM - Re: WTB dead Narco CP 135/136 or similar (Robert L. Nuckolls, III)
13. 08:47 PM - Re: Re: Thermocouple leads (David)
14. 08:59 PM - Re: Can Xfeed damage smaller battery. (bobbarrow)
15. 09:01 PM - Re: Thermocouple leads (Dennis Jones)
Message 1
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| Subject: | Re: Thermocouple leads |
Another "lightbulb" reply, thank you. I know I've read this in the
Connection, but still, a reminder doesn't go amiss.
Is this effect mitigated by having a common ground on the firewall, with a
braided strap to the engine? If the instruments are grounded to the forest
of tabs, and that's only a short distance along a fat piece of copper to
the engine...
James
On 1 February 2012 22:22, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> nuckolls.bob@aeroelectric.com**>
>
> At 01:20 PM 2/1/2012, you wrote:
>
>>
>> I'll second that. On the Dynon an improper ground on 1 device/sensor
>> can/will impact the reading on another. I used to have an old Cadillac
>> which when you moved the electric seat the high beams flashed. They called
>> it a feature.
>>
>> Glenn
>>
>
>
> Kudos Tim and Glenn. If the thermocouples are physically
> welded to the bottoms of their thermowells . . . and they
> often are . . . then what ever voltage difference that
> exists between the crankcase and the instrument's ground
> will ride on top of the thermocouple signals as a common
> mode voltage.
>
> All of thermocouple conditioning chips I've worked with
> for the last 20 years have a considerable tolerance to
> DC common mode interference but if the interference has
> alternator ripple on it, it might be another matter. Hence
> the questions about effects of alternator ON versus OFF.
>
> It would also be a good experiment to run a temporary
> instrument ground to the crankcase just to see if it
> makes any difference.
>
>
> Bob . . .
>
>
Message 2
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| Subject: | Re: Can Xfeed damage smaller battery. |
nuckolls.bob(at)aeroelect wrote:
>
>
> Sure. I presume then that your cross-feed is OPEN during
> starting which is good. The only time cross-feed can/should
> be closed for starting is IF BOTH batteries are sized for
> engine cranking duties.
>
Correct, the Xfeed would be open during all normal starting. That would prevent
a significant voltage drop during starting on Bus 1 from affecting my electronic
ignition and engine management system on Bus 2.
However if I was at some dark, remote and inhospitable place and I sensed that
the Odyssey 680 was struggling to light the fire I would be tempted to bring the
Odyssey 310 on line as well to see if the two batteries together would get
me going.
The Odyssey 310 is no slouch. It's used in a Kawasaki 1000 motorcycle.
The Odyssey 680 has an internal resistance of 7 milli-ohms and the Odyssey 310
is 27 milli-ohms. I am imaging that what that means is that the 680 will donate
any residual power it has to the bus more readily than the 310.
Apart from the potential re-charging problem associated with deep discharging the
Odyssey 310 is there any other reason that it should not be called on to act
in parallel in a tight situation.
Regards Bob Barrow
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=365442#365442
Message 3
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| Subject: | Re: Can Xfeed damage smaller battery. |
At 06:55 AM 2/2/2012, you wrote:
nuckolls.bob(at)aeroelect wrote:
>
> > Sure. I presume then that your cross-feed is OPEN during
> starting which is good. The only time cross-feed can/should
> be closed for starting is IF BOTH batteries are sized for
> engine cranking duties.
>
Correct, the Xfeed would be open during all normal starting. That
would prevent a significant voltage drop during starting on Bus 1
from affecting my electronic ignition and engine management system on Bus 2.
However if I was at some dark, remote and inhospitable place and I
sensed that the Odyssey 680 was struggling to light the fire I would
be tempted to bring the Odyssey 310 on line as well to see if the two
batteries together would get me going.
The Odyssey 310 is no slouch. It's used in a Kawasaki 1000 motorcycle.
The Odyssey 680 has an internal resistance of 7 milli-ohms and the
Odyssey 310 is 27 milli-ohms. I am imaging that what that means is
that the 680 will donate any residual power it has to the bus more
readily than the 310.
Apart from the potential re-charging problem associated with deep
discharging the Odyssey 310 is there any other reason that it should
not be called on to act in parallel in a tight situation.
No . . . risks to the battery for a single-event are
small. But it's difference in off-the-shelf internal
resistance suggests that it won't contribute much to
the effort of rotating the engine.
If the 680 is turning the engine at all, having a
robust spark probably contributes more to a successful
start than turning the engine faster. When I was studying
the Shower-of-Sparks magneto system I read that an
engine that was ready to run in terms of mixture
could be started by the slowest of hand-propping
motions to take one cylinder through TDC whereupon
the continuous stream of sparks would do the rest.
In any case, I've never encountered two airplanes
that enjoyed the same smooth talks and gentle strokes
when working at the corner of the cranking envelope.
After a time you will have discovered what works
best under adverse circumstances and that my include
tapping the 310 for assistance.
But I'd be willing to bet that if your batteries
are skillfully maintained and of sufficient capacity
to be useful as standby power, then probability
of an "adverse condition" due to battery limitations
is very low.
Having a Z-14 system installed should not quash your
curiosity about battery load and cap checks.
Bob . . .
Message 4
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| Subject: | WTB dead Narco CP 135/136 or similar |
I have a 1" (actually 1.1") slot on my radio stack that I want to fill with
some homebrew electronics and need a tray and whatever was in the tray. A
depth between 6 and 10 inches (the longer the better).
Anybody have anything clogging up the shop?
Send offers to johnl@loram.org
thanks, -john-
Message 5
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| Subject: | Re: Thermocouple leads |
That brings up a q that you might have answered in the original post:
Does each TC have it's own ground connected to it's own gauge? That is,
does each thermocouple supply two distinct lines to it's gauge? You
cannot use a common ground for each TC and only tie the signal wire to
the instrument.
David M.
Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 10:57 PM 1/31/2012, you wrote:
>> <jason@jasonbeaver.com>
>>
>> Does anyone know if there are any issues in running EGT/CHT
>> thermocouple wires along side the coax ignition leads from a
>> Lightspeed Plasma II ignition (the lines between the ignition box and
>> the coils)? My tech counselor said this could be a source of
>> inaccuracy in the temperature reading.
>
> I doubt it very much. The coax is double shielded
> (electro-static coupling ZERO) and the currents
> flowing in the center-conductor (outbound) exactly
> compliment return currents flowing in the shield.
>
> How much inaccuracy? You said they read high? All
> read high by the same amount? Are your probes isolated
> from engine ground or do they both electrically and
> thermally connect to the engine? Does turning the
> alternator on/off make any difference? Try turning
> EVERYTHING on to make this test. Present the alternator
> with the largest possibible load.
>
>
> Bob . . .
>
>
--
Tell the truth. Be honest. Be responsible to and for yourself.
I liked America when it was free and it's people were responsible and had morals.
Every gram of cocaine you buy from elsewhere contributes to an innocent being murdered
in Central and South America. Grow your own or Stop taking it.
Message 6
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| Subject: | Re: Thermocouple leads |
Also, any (new) junction will create an inaccuracy unless you calibrate
with the total installation.
David M.
Jason Beaver wrote:
> --> AeroElectric-List message posted by: Jason Beaver<jason@jasonbeaver.com>
>
> I'm not flying yet, so I have no way of testing. The tech counselor was just
speculating that this could be a source of inaccurate readings.
>
> Thanks,
>
> Jason
>
> Sent from my iPhone
>
> On Feb 1, 2012, at 10:04 AM, "ROGER& JEAN CURTIS"<mrspudandcompany@verizon.net>
wrote:
>
>
>>> Does anyone know if there are any issues in running EGT/CHT
>>> thermocouple wires along side the coax ignition leads from a
>>> Lightspeed Plasma II ignition (the lines between the ignition box
>>> and the coils)? My tech counselor said this could be a source of
>>> inaccuracy in the temperature reading.
>>>
>> I doubt it very much. The coax is double shielded
>> (electro-static coupling ZERO) and the currents
>> flowing in the center-conductor (outbound) exactly
>> compliment return currents flowing in the shield.
>>
>> How much inaccuracy? You said they read high? All
>> read high by the same amount? Are your probes isolated
>> from engine ground or do they both electrically and
>> thermally connect to the engine? Does turning the
>> alternator on/off make any difference? Try turning
>> EVERYTHING on to make this test. Present the alternator
>> with the largest possibible load.
>>
>>
>>
>>
>> Bob . . .
>>
>> I believe you are combining 2 questions from different
>> listers. One extended thermocouple wires and has a high reading and the
>> other is questioning if running thermocouple next to ignition wires causes
>> incorrect readings.
>>
>> Roger
>> <winmail.dat>
>>
>
>
>
--
Tell the truth. Be honest. Be responsible to and for yourself.
I liked America when it was free and it's people were responsible and had morals.
Every gram of cocaine you buy from elsewhere contributes to an innocent being murdered
in Central and South America. Grow your own or Stop taking it.
Message 7
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| Subject: | Re: Thermocouple leads |
At 06:01 PM 2/2/2012, you wrote:
>
>Also, any (new) junction will create an inaccuracy unless you
>calibrate with the total installation.
>
>David M.
>
A set of thermocouple leads can have quite a few
extraneous junctions without affecting accuracy
as long as (1) current in the leads is very low
indeed approaching zero. Such is the case with most
modern thermocouple instruments using specialized
integrated circuits for thermocouple signal
conditioning. And (2) EACH junction needs to be
repeated in number and kind on both sides of the
thermocouple pair.
This is described in more detail here:
http://aeroelectric.com/articles/excerpt.pdf
Bob . . .
Message 8
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| Subject: | Re: Thermocouple leads |
Not exactly grue, David... if it's a chromel/chromel junction and a
alumel/alumel junction, there's no potential developed across it, so
nothing to calibrate out. If, for instance, someone inserts some
copper wire, you'll have chromel/copper and copper chromel junctions,
and assuming they're separated, and at different temperatures, that
temperature difference CANNOT be assumed to be constant... so there's no
way to calibrate it out.
So... either it doesn't matter, or it can't be known. No middle ground.
Paul
On 2/2/2012 4:01 PM, David wrote:
>
> Also, any (new) junction will create an inaccuracy unless you
> calibrate with the total installation.
>
> David M.
>
>
Message 9
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| Subject: | Re: Thermocouple leads |
Hmmm, Bob... the physics doesn't support your assertion, unless you
(mistakenly I'd think) assume that all those junctions are somehow held
at the same temperature. And how would you accomplish that?
With the relatively common high impedance measuring devices, resistance
in the leads isn't really the issue... but adding uncontrolled junctions
at different temperatures can sure play havoc with accuracy.
Paul
On 2/2/2012 5:27 PM, Robert L. Nuckolls, III wrote:
> A set of thermocouple leads can have quite a few
> extraneous junctions without affecting accuracy
> as long as (1) current in the leads is very low
> indeed approaching zero. Such is the case with most
> modern thermocouple instruments using specialized
> integrated circuits for thermocouple signal
> conditioning. And (2) EACH junction needs to be
> repeated in number and kind on both sides of the
> thermocouple pair.
--
Please note my new email address!
millner@me.com
Message 10
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| Subject: | Re: Thermocouple leads |
The OP didn't say whether he was using old style instruments or newer,
(more digital) ones.
David M.
Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 06:01 PM 2/2/2012, you wrote:
>>
>> Also, any (new) junction will create an inaccuracy unless you
>> calibrate with the total installation.
>>
>> David M.
>>
>
> A set of thermocouple leads can have quite a few
> extraneous junctions without affecting accuracy
> as long as (1) current in the leads is very low
> indeed approaching zero. Such is the case with most
> modern thermocouple instruments using specialized
> integrated circuits for thermocouple signal
> conditioning. And (2) EACH junction needs to be
> repeated in number and kind on both sides of the
> thermocouple pair.
>
> This is described in more detail here:
>
> http://aeroelectric.com/articles/excerpt.pdf
>
>
> Bob . . .
>
>
--
Tell the truth. Be honest. Be responsible to and for yourself.
I liked America when it was free and it's people were responsible and had morals.
Every gram of cocaine you buy from elsewhere contributes to an innocent being murdered
in Central and South America. Grow your own or Stop taking it.
Message 11
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| Subject: | Re: Thermocouple leads |
I have the book, Bob. I must say, you are Ohminous!
David M.
Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 06:01 PM 2/2/2012, you wrote:
>>
>> Also, any (new) junction will create an inaccuracy unless you
>> calibrate with the total installation.
>>
>> David M.
>>
>
> A set of thermocouple leads can have quite a few
> extraneous junctions without affecting accuracy
> as long as (1) current in the leads is very low
> indeed approaching zero. Such is the case with most
> modern thermocouple instruments using specialized
> integrated circuits for thermocouple signal
> conditioning. And (2) EACH junction needs to be
> repeated in number and kind on both sides of the
> thermocouple pair.
>
> This is described in more detail here:
>
> http://aeroelectric.com/articles/excerpt.pdf
>
>
> Bob . . .
>
>
--
Tell the truth. Be honest. Be responsible to and for yourself.
I liked America when it was free and it's people were responsible and had morals.
Every gram of cocaine you buy from elsewhere contributes to an innocent being murdered
in Central and South America. Grow your own or Stop taking it.
Message 12
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| Subject: | Re: WTB dead Narco CP 135/136 or similar |
At 03:18 PM 2/2/2012, you wrote:
>
>I have a 1" (actually 1.1") slot on my radio stack that I want to fill with
>some homebrew electronics and need a tray and whatever was in the tray. A
>depth between 6 and 10 inches (the longer the better).
>
>Anybody have anything clogging up the shop?
>
>Send offers to johnl@loram.org
I've built custom trays and inserts to fit from
copper clad fiberglas sheets. Some careful work
with a shear and soldering iron will let you assemble
this material into about any practical size enclosure.
Here's a box I built up in a few hours to house
a 20 channel data acquisition system I needed
at Beech.
http://aeroelectric.com/Pictures/Data_Acquisition/Weeder_Module_DAS_1.jpg
http://aeroelectric.com/Pictures/Data_Acquisition/Weeder_Module_DAS_2.jpg
This construction is quite sturdy. You can make
any practical size enclosure with a minimum of tools.
Bob . . .
Message 13
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| Subject: | Re: Thermocouple leads |
That runs contrary to my initial training (early 80's), but new things
are discovered all the time! Thanks, Paul.
David
Paul Millner wrote:
>
> Not exactly grue, David... if it's a chromel/chromel junction and a
> alumel/alumel junction, there's no potential developed across it, so
> nothing to calibrate out. If, for instance, someone inserts some
> copper wire, you'll have chromel/copper and copper chromel junctions,
> and assuming they're separated, and at different temperatures, that
> temperature difference CANNOT be assumed to be constant... so there's
> no way to calibrate it out.
>
> So... either it doesn't matter, or it can't be known. No middle ground.
>
> Paul
>
> On 2/2/2012 4:01 PM, David wrote:
>>
>> Also, any (new) junction will create an inaccuracy unless you
>> calibrate with the total installation.
>>
>> David M.
>>
>>
>
>
--
Tell the truth. Be honest. Be responsible to and for yourself.
I liked America when it was free and it's people were responsible and had morals.
Every gram of cocaine you buy from elsewhere contributes to an innocent being murdered
in Central and South America. Grow your own or Stop taking it.
Message 14
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| Subject: | Re: Can Xfeed damage smaller battery. |
Bob, thank you very much for your assistance. I now feel that I am up to speed
on this issue. The dark gray clouds of doubt have been lifted. :)
Cheers Bob Barrow
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=365513#365513
Message 15
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| Subject: | Re: Thermocouple leads |
It is an EPI-800 electronic system with a DPU.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=365514#365514
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