Today's Message Index:
----------------------
1. 06:29 AM - Fuse Block Design Debate (Mark Neubauer)
2. 06:45 AM - Re: First day of school jitters . . . (Robert L. Nuckolls, III)
3. 07:16 AM - Re: Grounding,LED Toggle Switches (Robert L. Nuckolls, III)
4. 07:27 AM - Re:Fuse Block Design Debate (flmike)
5. 08:42 AM - Re: KT-76A Pinout Clarification (John Wiegenstein)
6. 10:13 AM - Re: Shielded sensor wires (Terry Watson)
7. 12:40 PM - Re: Question! (Ernest Kells)
8. 02:36 PM - Re: Shielded sensor wires (Trampas)
9. 07:10 PM - Re: Question! (Wayne Berg)
10. 08:18 PM - Re: Question! (Robert L. Nuckolls, III)
11. 08:40 PM - Re: Fuse Block Design Debate (Robert L. Nuckolls, III)
12. 08:43 PM - Re: Re: KT-76A Pinout Clarification (Robert L. Nuckolls, III)
13. 09:03 PM - Re: Shielded sensor wires (Robert L. Nuckolls, III)
14. 11:27 PM - Searching-Fast on's / Terminal Blocks (Don Boardman)
Message 1
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| Subject: | Fuse Block Design Debate |
--> AeroElectric-List message posted by: "Mark Neubauer" <mark.neubauer@genmar.com>
Bob, et.al.
I love a good debate, and you took me to task on some of my points made last week,
so let me respond.....
Bob said: The fast-on plows a groove in the tab . . . forces
greater than the tab material can resist have bared
fresh, sub-surface material. Further, as the joint
ages, pressures do not materially change (unless you
have funky fast-ons of poor material) so ANY motion
tends to dig the terminal's magic-points-of-contact
in deeper.
Can't argue with much here except the phrase "forces greater than the tab material"
- not sure what that means. I agree, any motion will dig deeper into the
tab, but in the process scrapes off any (tin) plating and promotes oxidation of
the substrate (usually copper)
Bob said: if "better" means higher contact pressure over the lifetime
of the joint, then the fast-on has it hands down.
If you have some other definition of better, we
need to know what it is and examine its physics.
With any joint, whether thermal or electrical, two physical factors come into play
- area and pressure. The Fast-On tab wins hands down on pressure but looses
on contact area. In measuring one of my connectors for 20 ga. wire, the high
pressure contact ridges (the end of the rolled edges) measure .015" thick and
.3" long. This is an area of .015" x .3" x 2, or .009 in
2. Using your logic about contact pressure, I would think that the back side of
the connector, where the large contact area does exist, cannot achieve pressures
as high as a screwed joint, so your arguments above do not apply here. Conversely,
a ring terminal has a contact area of about .08 in
2, or about 10 times the Fast-On's area. I'm not interested in getting into the
mechanics of screw-torque vs. pressure on a screwed connection with 32 threads/turn,
with a certain surface friction and class of thread. My only point is
that I think we're splitting hairs on one connection method being demonstrably
better than the other. Screwed posts have been around since Edison's days, and
if it wasn't reliable, then why do we use it on battery terminals, contactor
terminals, alternator B posts, starter motors, and feed lines to the Fast-On
style fuse block? The advantage of Fast-On tabs is just that - they are faster
to put on.
Bob said: Why is this a good deal? I thought the super low price
and availably of fuse-holder slots versus acres-of-breakers
offered us a way to have EVERY accessory enjoy its OWN
independently protected source.
Bob, even in your book on page 10-2 you allow for some items to share a single
fuse or breaker. My GlaStar will have three fuse blocks, with a total of 28 fused
circuits, so I would not say I have economized from this standpoint. I'm only
saying that a ring terminal would be a convenient point for feeding two lines
with the same purpose, like feeding two lighting dimmers for two separate
controllable lighting circuits.
Bob said: But you'll never see a chrome plated terminal or connector
product offered by AMP, Molex, Cannon, Ampehnol, etc. etc.
Wonder why . . . .
What are you talking about?!? Just about every RF and audio connector I have ever
seen is chrome plated, unless you go to the expensive gold-plated models. I
can't think of one family of connector (for RF transmission) where inconsistent
contact resistance could be more problematic. Chrome plating is not used on
certain connectors because it cannot be soldered, is very hard, and it cannot
withstand severe flexing (chrome is brittle). It's difficult to economically
beat chrome plating for surface hardness and corrosion resistance. (Besides, it
also looks nice on my Buick's bumper)
Mark
Message 2
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| Subject: | Re: First day of school jitters . . . |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>
>Comments/Questions: I'm nervous this will be over my head from the
>'get-go'. I'll do my best to have at least the better part of the
>AeroElectric Connection read before the seminar. I'm a first time builder,
>RV-7, finishing up the fuselage over the next few months and then ready to
>start the panel. It sure would be nice to get the electrical system right
>the first time around.
Not to worry. This program is for folks like yourself. The
electrical system is assembled from a big box of tinker-toys.
Each component is simple and easily understood. Like tinker-toys,
they can be assembled in a variety of ways depending on your
goals are for the airplane . . . and easily modified later if
you find that some particular goal has changed or is not being
met.
I know it's a strange new vernacular but once you breach
what is essentially a language barrier, you'll be able to discuss
your goals with others and exploit their ideas and successes.
Join the AeroElectric-List, attend this class and be assured
that putting the electrical system together should be the
fun part of building an airplane. There are hundreds of folks
just like yourself who are getting this done every year. We're
all here to help.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 3
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| Subject: | Re: Grounding,LED Toggle Switches |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:28 PM 1/18/2004 -0500, you wrote:
>--> AeroElectric-List message posted by: "Terrence Gardner"
><ttandt@mindspring.com>
>
>Bob,
>Thanks for the Jeff City seminar. I found it particularly useful. Perhaps
>we can get you to the Carolinas in the coming year.
Sure, put out some feelers in your area. No reason we couldn't
do one in your neck of the woods.
>My first question is your opinion on running wing tip/ position, landing
>light, and taillight grounds to the fire wall mounted main ship ground. Is
>any advantage gained?
No. In a metal airplane, I'd ground nav lights, strobe power supply,
landing and taxi lights and pitot heaters locally to airframe.
> My initial impression is no. I do intend to bring all
>other cockpit/panel grounds individually to the B&C Faston ground block
>mounted on the FW as described in the AEC.
Good move . . .
>
>Secondly, are you familar with the NKK 2100 SeriesLED illuminated toggle
>switches. I was considering making all night operated switches these in
>order to minimize the amount of cockpit lighting required yet make them
>instantly identifiable.
I have no personal knowledge of these. I downloaded the
data sheets from
http://www.nkkswitches.com
and note that these clever little switches are offered
only in miniature sizes and that they don't offer any
of the progressive transfer versions like B&C's
2-10 and 2-50.
These can certainly be used but you'll find that some
functions will require external relays for buffering
higher current loads and/or achieving the special
functions. This is not a cost issue. . . . relays
are cheap. If you want the appearance offered by this
product, it can certainly be accomplished.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 4
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| Subject: | RE:Fuse Block Design Debate |
--> AeroElectric-List message posted by: flmike <flmike2001@yahoo.com>
Mark,
Regarding the chrome plating, are you sure you're not
mistaking bright nickel plate for chrome? None of the
RF connector catalogs I checked list chrome as a
plating option. Bright nickel, silver, and gold are
some of the plating options offered by Amphenol,
FCI/Berg, Molex, Kings, and Trompeter. No mention of
chrome.
Mike
__________________________________
Message 5
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| Subject: | Re: KT-76A Pinout Clarification |
--> AeroElectric-List message posted by: "John Wiegenstein" <N727JW@hellerwiegenstein.com>
>Subject: Re: AeroElectric-List: KT-76A Pinout Clarification
>--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
At 08:10 PM 1/22/2004 -0800, you wrote:
>>--> AeroElectric-List message posted by: "John Wiegenstein"
>><n727jw@hellerwiegenstein.com>
>>>
>>OK, the KT-76A has shown up in the extensive (expensive?) Honeywell box.
>>I've downloaded Bob's pinout PDF for this unit, but want to make sure its
>>wired up correctly. The connector that came with the unit does not have
a
>>"one way" tab to prevent a reversed assembly, but the pin numbers and
>>letters on the connector are as shown in Bob's pinout, and the edge
>>connector on the unit has a slot near one end, such that the numbers and
>>letters seem to match. But before I accidentally let all the smoke out
of
>>the insides, has anyone done a recent install and can confirm this?
> First, if you have the KT76A, then I'm curious as to where
> you got the pinout. Until a few minutes ago, only the KT76/78
> drawing was posted the KT76A/76C/78A drawing at:
> http://www.aeroelectric.com/Installation_Data/KT76A-76C-78A.pdf
> This drawing shows the keyway plug being inserted between pins
> 3/4, C/D. This should get your plug lined up properly and confirm
> that numbered pins are on the top surface of the ECB connector
> sticking out through the hole in the case.
Bob, thanks for the feedback on this. Everything is wired up fine and
checks out with your comments above, and when the AK350 encoder arrived
Saturday that made everything clear on the encoder to transponder
connections.
As far as the availability of the KT-76A PDF on your site, the existing link
for the KT-76 printed out 3 pages and (unless I'm hallucinating) had KT-76A
specific details on page 2 and 3. The new link above looks to be the same
as pages 2 and 3 of the old one, at least from memory as I sit here in the
office.
Anyway, looks like I'm good to go. The AK350 encoder and ICOM A200
transceiver just arrived, so with a little more work I should be ready to
test everything out. Thanks again for your ongoing assistance - can't
imagine how OBAM birds got built before the internet came along! :-)
John H. Wiegenstein
Hansville, WA
RV-6 #23961 - N727JW (reserved)
Message 6
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| Subject: | Shielded sensor wires |
--> AeroElectric-List message posted by: "Terry Watson" <terry@tcwatson.com>
If you're extending thermocouple wires, you need to use the
same style of thermocouple material for extending them. All
of those sensors are low impedance devices and are neither
antagonistic to other systems or much of a potential victim.
I'm mystified as to why they would be offered as shielded.
Bob . . .
Thermocouple wires
Bob,
Thanks for the reply to my question about thermocouple wires. It is still
not completely clear in my mind how best to handle this, so I checked the
Matronics archives for some previous discussions. One particularly helpful
one was where you gave reference to Omega's website where I can order spools
of thermocouple wire.
I believe the EGT thermocouples are manufactured by Electronics
International. The thermocouple comes with maybe four or six feet of two
conductor solid core wire, shielded and terminating in a male and a female
spade connector. I ordered four of their six-foot extension wires (at
$32.00 each), which are also solid core and have spade connectors each end
that match up with the original wires
I need the thermocouple wires to end up as a part of a 37-pin d-sub
connector that connects to the CPU of the Blue Mountain EFIS/one system. I
am quite concerned that these stiff single strand wires are not going to
take the handling that this d-sub connector is going to get. I had been
advised that I could switch to standard 22 ga wire, as long as the change
from the thermocouple wires were behind the firewall where both conductors
would be in the same environment. I thought this must be because the CPU
can calibrate whatever information it gets from the thermocouple into a
useable value to be displayed on the screen.
So now my questions:
First, is it reasonable to believe what I had been told about the CPU being
able to calibrate the signals when there is some standard copper wiring
between the thermocouple and the CPU? If so, would it be reasonable to just
cut off the spade connectors on the thermocouple wire and use butt splices
between the copper and the thermocouple wire?
Second, if that is not the case, would it make sense to order some stranded
thermocouple wire from Omega for the final run to the 37 pin d-sub? I need
to extend the wires anyway, and the stranded wire should take the flexing
better than the solid that I have.
How should this be spliced to the existing solid core wire? Do I need to
silver solder it?
Thanks Bob. I really appreciate your help.
Terry
RV-8A
Seattle
Message 7
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--> AeroElectric-List message posted by: "Ernest Kells" <ernest.kells@sympatico.ca>
Bob and/or Others:
I am using the two battery/one alternator approach for a basic VFR RV-9A. I
have an Oddyssey PC680 battery (14.4 lbs). Instead of using a "little"
battery as the second power supply what do you think of using TWO PC680s.
The two batteries would have a minor weight penalty over Vans recommeded
Concorde RG-25. However, I could then cycle the two batteries - replacing
the "main" battery up to twice as often - or twice as long. I wouldn't
have to worry about sourcing the main PC680 while on extended X/C trips
(winter getaways, etc). I don't see any problems - other than the 4-5 lbs
of weight ( I can tolerate more upfront weight ).
Ernest Kells - RV-9A O235-N2C, Wood Prop
90% Complete - instruments
Message 8
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| Subject: | Shielded sensor wires |
--> AeroElectric-List message posted by: "Trampas" <tstern@nc.rr.com>
I figured I would put in my $0.02...
First a little thermocouple theory, thermocouples measure a temperature
difference. That is a thermocouple measures the difference between the
temperature at your EGT or CHT probe point and the point where the
connection changes back to some other metal, aka copper. So for example the
Westach EGT and CHT gauges assumes that the temperature where the junction
returns to copper is always 68 degrees. Therefore if your thermocouple wires
return to copper in the cockpit and where it is 90 degrees you have 22
degrees error in your measurement. That is where the thermocouple wires
change to the same wire type permanently this is the reference junction
temperature point.
Now one of the sticking points is connectors. That is if I have a
thermocouple extension wire which is connected to the probe wiring using
copper connectors, then what happens. Well basically if both of the
thermocouple wires have the same connectors and are at the same temperature
then there is no error. Think of it as one connector, on positive wire,
creates a voltage and the other, on the negative wire, subtracts the same
voltage since they are at the same temperature, thus no error.
So basically to answer your question, ask the Blue Mountain folks how they
did there reference junction temperature measurement. Most likely they used
a constant 68 degrees, thus going to copper wires inside the cockpit will
not be a problem. If they did use a constant 68 degrees as reference
temperature and you ran the thermocouple wires all the way back to unit you
will have about the same error. If they actually measure the D-sub connector
temperature then I would run thermocouple wire all the way to the D-sub for
most accurate measurement.
Personally I use Omega's 20 gauge stranded thermocouple wire, with Teflon
insulation, for extension wire. I can give part numbers if you like. Also on
my engine monitor I have it measuring the reference junction temperature
such that I have only a few degrees error from the NIST measurement standard
across the entire range of the thermocouples.
Also one of your questions was about shielding the thermocouple wires. The
probes for the EGTs and CHTs usually have metal shielding more for heat and
abrasion than for electrical shielding. The thermocouple wires are very low
impedance sensors, which means it is hard to generate noise on the wiring.
Therefore electrical shielding is not needed. Now I say this but I have
heard stories about instruments which have some ground loop problems which
is different than the shielding.
The ground loop problem is rather simple. On an air cooled engine each head
is connected to the main block using steel bolts and the heads are aluminum
therefore each head acts as a thermocouple it's self. Therefore there can be
a small voltage difference from the head for cly #1 to #2. Thermocouples
operate on a small voltage, under .050 Volts, thus small ground potential
differences between heads have been known to cause a lot of problems on some
engine monitors. Therefore one of the things I have made sure of on my
engine monitor is that the unit can handle ground noise up to +/2 Volts on
the thermocouple inputs. This ground noise problem was so bad I heard of one
company actually making probes which are isolated from the cylinder head
grounds.
Regards,
Trampas
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Terry
Watson
Subject: RE: AeroElectric-List: Shielded sensor wires
--> AeroElectric-List message posted by: "Terry Watson" <terry@tcwatson.com>
If you're extending thermocouple wires, you need to use the
same style of thermocouple material for extending them. All
of those sensors are low impedance devices and are neither
antagonistic to other systems or much of a potential victim.
I'm mystified as to why they would be offered as shielded.
Bob . . .
Thermocouple wires
Bob,
Thanks for the reply to my question about thermocouple wires. It is still
not completely clear in my mind how best to handle this, so I checked the
Matronics archives for some previous discussions. One particularly helpful
one was where you gave reference to Omega's website where I can order spools
of thermocouple wire.
I believe the EGT thermocouples are manufactured by Electronics
International. The thermocouple comes with maybe four or six feet of two
conductor solid core wire, shielded and terminating in a male and a female
spade connector. I ordered four of their six-foot extension wires (at
$32.00 each), which are also solid core and have spade connectors each end
that match up with the original wires
I need the thermocouple wires to end up as a part of a 37-pin d-sub
connector that connects to the CPU of the Blue Mountain EFIS/one system. I
am quite concerned that these stiff single strand wires are not going to
take the handling that this d-sub connector is going to get. I had been
advised that I could switch to standard 22 ga wire, as long as the change
from the thermocouple wires were behind the firewall where both conductors
would be in the same environment. I thought this must be because the CPU
can calibrate whatever information it gets from the thermocouple into a
useable value to be displayed on the screen.
So now my questions:
First, is it reasonable to believe what I had been told about the CPU being
able to calibrate the signals when there is some standard copper wiring
between the thermocouple and the CPU? If so, would it be reasonable to just
cut off the spade connectors on the thermocouple wire and use butt splices
between the copper and the thermocouple wire?
Second, if that is not the case, would it make sense to order some stranded
thermocouple wire from Omega for the final run to the 37 pin d-sub? I need
to extend the wires anyway, and the stranded wire should take the flexing
better than the solid that I have.
How should this be spliced to the existing solid core wire? Do I need to
silver solder it?
Thanks Bob. I really appreciate your help.
Terry
RV-8A
Seattle
Message 9
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--> AeroElectric-List message posted by: "Wayne Berg" <wfberg@msn.com>
I have the same setup in my RV-8. I will be interested in Bob's reply.
Wayne Berg
----- Original Message -----
From: Ernest Kells
Subject: Re: AeroElectric-List: Question!
--> AeroElectric-List message posted by: "Ernest Kells" <ernest.kells@sympatico.ca>
Bob and/or Others:
I am using the two battery/one alternator approach for a basic VFR RV-9A. I
have an Oddyssey PC680 battery (14.4 lbs). Instead of using a "little"
battery as the second power supply what do you think of using TWO PC680s.
The two batteries would have a minor weight penalty over Vans recommeded
Concorde RG-25. However, I could then cycle the two batteries - replacing
the "main" battery up to twice as often - or twice as long. I wouldn't
have to worry about sourcing the main PC680 while on extended X/C trips
(winter getaways, etc). I don't see any problems - other than the 4-5 lbs
of weight ( I can tolerate more upfront weight ).
Ernest Kells - RV-9A O235-N2C, Wood Prop
90% Complete - instruments
Message 10
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 07:09 PM 1/26/2004 -0800, you wrote:
>--> AeroElectric-List message posted by: "Wayne Berg" <wfberg@msn.com>
>
>I have the same setup in my RV-8. I will be interested in Bob's reply.
>Wayne Berg
>
>----- Original Message -----
>From: Ernest Kells
>To: aeroelectric-list@matronics.com
>Subject: Re: AeroElectric-List: Question!
>
>--> AeroElectric-List message posted by: "Ernest Kells"
><ernest.kells@sympatico.ca>
>
>Bob and/or Others:
>I am using the two battery/one alternator approach for a basic VFR RV-9A. I
>have an Oddyssey PC680 battery (14.4 lbs). Instead of using a "little"
>battery as the second power supply what do you think of using TWO PC680s.
>The two batteries would have a minor weight penalty over Vans recommeded
>Concorde RG-25. However, I could then cycle the two batteries - replacing
>the "main" battery up to twice as often - or twice as long. I wouldn't
>have to worry about sourcing the main PC680 while on extended X/C trips
>(winter getaways, etc). I don't see any problems - other than the 4-5 lbs
>of weight ( I can tolerate more upfront weight ).
>Ernest Kells - RV-9A O235-N2C, Wood Prop
>90% Complete - instruments
My favorite combination is a pair of 17 a.h. RG
batteries that weigh about 15 pounds each. You can
save some money by using the Panasonic batteries
instead of PC680 . . . more economical for the
yearly change-out style of preventative maintenance.
The batteries don't have to be indentical. Run a
Panasonic in conjunction with the 680 for a year
and put a second Panasonic in at next annual.
Bob . . .
Message 11
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| Subject: | Re: Fuse Block Design Debate |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:26 AM 1/26/2004 -0600, you wrote:
>--> AeroElectric-List message posted by: "Mark Neubauer"
><mark.neubauer@genmar.com>
>
>Bob, et.al.
>
>I love a good debate, and you took me to task on some of my points made
>last week, so let me respond.....
>
>Bob said: The fast-on plows a groove in the tab . . . forces
> greater than the tab material can resist have bared
> fresh, sub-surface material. Further, as the joint
> ages, pressures do not materially change (unless you
> have funky fast-ons of poor material) so ANY motion
> tends to dig the terminal's magic-points-of-contact
> in deeper.
>
>Can't argue with much here except the phrase "forces greater than the tab
>material" - not sure what that means.
poor semantics . . . "forces beyond that which the tab material can
resist . . . the fast-on makes sharp edged contact with the tab and
upsets the metal at the surface".
> I agree, any motion will dig deeper into the tab, but in the process
> scrapes off any (tin) plating and promotes oxidation of the substrate
> (usually copper)
except where pressure of the contact area precludes
corrosion. Granted, this is not without limits. Fastons
are not appropriate for severe environments. I'd
think twice about salt-water marine applications.
But airplanes are really rather benign.
>Bob said: if "better" means higher contact pressure over the lifetime
> of the joint, then the fast-on has it hands down.
> If you have some other definition of better, we
> need to know what it is and examine its physics.
>
>With any joint, whether thermal or electrical, two physical factors come
>into play - area and pressure. The Fast-On tab wins hands down on pressure
>but looses on contact area. In measuring one of my connectors for 20 ga.
>wire, the high pressure contact ridges (the end of the rolled edges)
>measure .015" thick and .3" long. This is an area of .015" x .3" x 2, or
>.009 in
Current carrying ability is a function of area and gas
tightness is a function of pressure.
>2. Using your logic about contact pressure, I would think that the back
>side of the connector, where the large contact area does exist, cannot
>achieve pressures as high as a screwed joint, so your arguments above do
>not apply here.
They do not. The back side of a fast on is there to keep
the two sides together. While it contributes to conductivity
while new, it's not critical to the future due to it's
large area, low pressure contact which is not resistant
to environmental effects.
> Conversely, a ring terminal has a contact area of about .08 in
>2, or about 10 times the Fast-On's area. I'm not interested in getting
>into the mechanics of screw-torque vs. pressure on a screwed connection
>with 32 threads/turn, with a certain surface friction and class of thread.
>My only point is that I think we're splitting hairs on one connection
>method being demonstrably better than the other.
No, it's apples and oranges. Ring terminals get their
gas-tight qualities from a process that is user controlled.
Fast-ons are designed to be independent of process effects.
Both are just fine if their respective limits are recognized
and considered in the design.
> Screwed posts have been around since Edison's days, and if it wasn't
> reliable, then why do we use it on battery terminals, contactor
> terminals, alternator B posts, starter motors, and feed lines to the
> Fast-On style fuse block? The advantage of Fast-On tabs is just that -
> they are faster to put on.
"reliable" is comparative. Never said threaded terminals
are "bad" . . . just that fast-on are have features that
make them preferred. It's like crimp versus solder. Both
technologies are fine within their respective limits.
>Bob said: Why is this a good deal? I thought the super low price
> and availably of fuse-holder slots versus acres-of-breakers
> offered us a way to have EVERY accessory enjoy its OWN
> independently protected source.
>
>Bob, even in your book on page 10-2 you allow for some items to share a
>single fuse or breaker. My GlaStar will have three fuse blocks, with a
>total of 28 fused circuits, so I would not say I have economized from this
>standpoint. I'm only saying that a ring terminal would be a convenient
>point for feeding two lines with the same purpose, like feeding two
>lighting dimmers for two separate controllable lighting circuits.
Point well taken. But you can also crimp multiple wires
into a single fast-on terminal. See
http://www.aeroelectric.com/articles/multiplewires/multiplewires.html
>Bob said: But you'll never see a chrome plated terminal or connector
> product offered by AMP, Molex, Cannon, Ampehnol, etc. etc.
> Wonder why . . . .
>
>What are you talking about?!? Just about every RF and audio connector I
>have ever seen is chrome plated, unless you go to the expensive
>gold-plated models. I can't think of one family of connector (for RF
>transmission) where inconsistent contact resistance could be more
>problematic. Chrome plating is not used on certain connectors because it
>cannot be soldered, is very hard, and it cannot withstand severe flexing
>(chrome is brittle). It's difficult to economically beat chrome plating
>for surface hardness and corrosion resistance. (Besides, it also looks
>nice on my Buick's bumper)
Don't think chrome is used in electrical contact surfaces.
The HOUSINGS of connectors can be chromed. There are a number of
'bright' finishes with much better electrical characteristics
than chrome that are often mistaken for chrome.
Bob . . .
Message 12
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| Subject: | Re: KT-76A Pinout Clarification |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>
>Bob, thanks for the feedback on this. Everything is wired up fine and
>checks out with your comments above, and when the AK350 encoder arrived
>Saturday that made everything clear on the encoder to transponder
>connections.
great . . .
>As far as the availability of the KT-76A PDF on your site, the existing link
>for the KT-76 printed out 3 pages and (unless I'm hallucinating) had KT-76A
>specific details on page 2 and 3. The new link above looks to be the same
>as pages 2 and 3 of the old one, at least from memory as I sit here in the
>office.
I'm mystified. When I checked the server directory, I didn't
see the A series drawings. I went to the archives and re-created
them for posting just before I replied last night. Must be
server gremlins again . . . pesky critters . . .
>Anyway, looks like I'm good to go. The AK350 encoder and ICOM A200
>transceiver just arrived, so with a little more work I should be ready to
>test everything out. Thanks again for your ongoing assistance - can't
>imagine how OBAM birds got built before the internet came along! :-)
Oh, they made it . . . but in fewer numbers and with more
expensive educational experiences. The 'net is the backbone
of GA future in small aircraft.
Bob . . .
Message 13
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| Subject: | Shielded sensor wires |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 05:32 PM 1/26/2004 -0500, you wrote:
>--> AeroElectric-List message posted by: "Trampas" <tstern@nc.rr.com>
>
>I figured I would put in my $0.02...
>
>First a little thermocouple theory, thermocouples measure a temperature
>difference. That is a thermocouple measures the difference between the
>temperature at your EGT or CHT probe point and the point where the
>connection changes back to some other metal, aka copper. So for example the
>Westach EGT and CHT gauges assumes that the temperature where the junction
>returns to copper is always 68 degrees. Therefore if your thermocouple wires
>return to copper in the cockpit and where it is 90 degrees you have 22
>degrees error in your measurement. That is where the thermocouple wires
>change to the same wire type permanently this is the reference junction
>temperature point.
reference junctions are either tied down to some known temperature
like an ice bath (0 degrees C) See figure 14-10 in:
http://www.aeroelectric.com/articles/excerpt.pdf
or they are ambient compensated like the example shown in figure
14-12 view B. It's a poor design that "assumes" a remote reference
junction will reside at 68 degrees or any other temperature unless
pains are taken to make sure they stay at that temperature.
>Now one of the sticking points is connectors. That is if I have a
>thermocouple extension wire which is connected to the probe wiring using
>copper connectors, then what happens. Well basically if both of the
>thermocouple wires have the same connectors and are at the same temperature
>then there is no error. Think of it as one connector, on positive wire,
>creates a voltage and the other, on the negative wire, subtracts the same
>voltage since they are at the same temperature, thus no error.
>
>So basically to answer your question, ask the Blue Mountain folks how they
>did there reference junction temperature measurement. Most likely they used
>a constant 68 degrees, thus going to copper wires inside the cockpit will
>not be a problem. If they did use a constant 68 degrees as reference
>temperature and you ran the thermocouple wires all the way back to unit you
>will have about the same error. If they actually measure the D-sub connector
>temperature then I would run thermocouple wire all the way to the D-sub for
>most accurate measurement.
>
I would be very disappointed in Blue Mountain if their system
is so constructed. It's almost a sure bet that their thermocouple
amplifiers are commercial devices like this Analog Devices part:
http://www.analog.com/UploadedFiles/Data_Sheets/421725987AD594_5_c.pdf
In this case, the designer intends that you bring thermocouple
wire all the way to the connector at their signal conditioning
box. This should be apparent from simple examination of their
wiring diagrams. What do they tell you to do with thermocouple
sensors?
>Personally I use Omega's 20 gauge stranded thermocouple wire, with Teflon
>insulation, for extension wire. I can give part numbers if you like. Also on
>my engine monitor I have it measuring the reference junction temperature
>such that I have only a few degrees error from the NIST measurement standard
>across the entire range of the thermocouples.
>
>Also one of your questions was about shielding the thermocouple wires. The
>probes for the EGTs and CHTs usually have metal shielding more for heat and
>abrasion than for electrical shielding. The thermocouple wires are very low
>impedance sensors, which means it is hard to generate noise on the wiring.
>Therefore electrical shielding is not needed. Now I say this but I have
>heard stories about instruments which have some ground loop problems which
>is different than the shielding.
>
>The ground loop problem is rather simple. On an air cooled engine each head
>is connected to the main block using steel bolts and the heads are aluminum
>therefore each head acts as a thermocouple it's self. Therefore there can be
>a small voltage difference from the head for cly #1 to #2. Thermocouples
>operate on a small voltage, under .050 Volts, thus small ground potential
>differences between heads have been known to cause a lot of problems on some
>engine monitors. Therefore one of the things I have made sure of on my
>engine monitor is that the unit can handle ground noise up to +/2 Volts on
>the thermocouple inputs. This ground noise problem was so bad I heard of one
>company actually making probes which are isolated from the cylinder head
>grounds.
Isolated probes are preferred. My designs usually expect them. If isolated
probes are not supplied/specified, then it's REALLY important to have
the firewall mounted single point ground for stuff on the panel . . . which
is attached to the crankcase with a really fat ground strap. Blue Mountain's
installation instructions should touch on this if it's important. If they're
using the Analog Devices chips, the signal conditioner is relatively immune
to common mode voltages of the magnitude suggested by Trampas. See page 4
of the AD594 data sheet, second paragraph.
Bob . . .
Message 14
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| Subject: | Searching-Fast on's / Terminal Blocks |
--> AeroElectric-List message posted by: Don Boardman <dboardm3@twcny.rr.com>
Hi All,
B & C has been my electrical supplier for my Moose project. I have been very
pleased with their products and service. Two things they do not have in
their inventory.
1. A short strip of male quick connect fast on's to go on the engine side of
the firewall to complement the 24 terminal ground block from B & C.
Another 24 block is $26 a little steep for just a few engine side grounds.
I have done a bunch of Google searches and found a manufacturer but no
retail.
Any Leads?
2. I have been looking for some quality terminal blocks. The installation of
out Aerocet Amphib Floats calls for terminal blocks to make the wire
transitions from fuselage to floats (a bunch of wires for all that gear up
and down stuff). I finally found a style that I though would work well
manufactured by Marco. A mill spec MS27212 screw post block. Just the
ticket! Great! Then found them for sale at Chief Aircraft ...
20 terminal block (which can be cut) with # 6 screw posts ONLY $69.95. ARE
THEY OUT OF THEIR MINDS. Also a 16 terminal #10 screw (could really torque
those babies) a bargin at $31.95.
Maybe I will use D-sub connectors.
Help!
Comments,
Don B
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