Today's Message Index:
----------------------
1. 06:00 AM - Re: proper cable for engine instrument (Steve Stearns)
2. 07:48 AM - Electronics 101...Advanced. (Eric M. Jones)
3. 11:20 AM - Re: proper cable for engine instrument (Robert L. Nuckolls, III)
4. 02:36 PM - Re: Electronics 101...Advanced. (Carlos Trigo)
5. 05:20 PM - Re: Electronics 101...Advanced. (MTBehnke)
Message 1
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Subject: | Re: proper cable for engine instrument |
Bob,
Recently, you have made a couple references to solid thermocouple grade
wire (via Omega website links), rather than the stranded thermocouple
extension grade wire I was planning on using, for long runs from
thermocouple to the instrument. What is the advantages/disadvantages of
one over the other for these long runs? I based my thinking on an
understanding that stranded is more durable than equal sized solid in
aircraft applications.
Thanks,
Steve Stearns
Boulder/Longmont, Colorado
CSA,EAA,IAC,AOPA,PE,ARRL,BARC (but ignorant none-the-less)
Restoring (since 1/07): N45FC O235 Longeze Cothern/Friling CF1 (~1000 Hrs)
Flying (since 9/86): N43732 A65 Taylorcraft BC12D
Message 2
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Subject: | Electronics 101...Advanced. |
Occasionally I get an inquiry from a customer who is checking out his electrical
system and finds what they view as an error--They test solid state components
that are supposed to be OFF, or diodes that are supposed to not conduct, and
they measure a voltage on the output. This they think must indicate a failure.
Usually, I can't figure this out from the description until some emails or calls
have been exchanged, but it always boils down to the following--
The existence of an "output voltage", even a very substantial voltage, does not
mean much. If there was a load connected from the output, there would be no measured
voltage (on a standard voltmeter).
Voltmeters always possess a load. Digital types are usually 10 MegOhms, which is
small enough to interfere very little with the circuit being measured, but for
many applications can lead to incorrect or puzzling results--for example measuring
dry cell batteries, or the output of solid state switches or diodes--In
these tasks, output load is important. (It is trivial to make a voltmeter with
GigaOhms or greater resistance but they find little use except in the rare
experiment.)
"The problem with the world is that only the intelligent people want to be
smarter, and only the good people want to improve."
- Eolake Stobblehouse
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 3378#203378
Message 3
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Subject: | Re: proper cable for engine instrument |
At 05:55 AM 9/9/2008 -0600, you wrote:
>
>Bob,
>
>Recently, you have made a couple references to solid thermocouple grade
>wire (via Omega website links), rather than the stranded thermocouple
>extension grade wire I was planning on using, for long runs from
>thermocouple to the instrument. What is the advantages/disadvantages of
>one over the other for these long runs? I based my thinking on an
>understanding that stranded is more durable than equal sized solid in
>aircraft applications.
Either is fine. I have both on the shelves. I prefer stranded
20AWG wire for crimping into d-sub pins but the preference
is subtle . . . I perceive a tiny advantage in smaller strands
yielding to a gas-tight crush within the pin.
If you have access to solid, don't go buy stranded to
replace it. But if you're ordering from scratch, the
stranded is a bit more attractive.
Bob . . .
Message 4
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Subject: | Electronics 101...Advanced. |
Eric
Now that you initiated a pedagogic thread, you should go to the bottom
of
it.
For us, non-EE and electronically-challenged (should I say ignorant?)
guys,
that is a real situation! For me, it=92s a =93Been-there-done-that=94
case =85 :-)
I did measure, with my digital voltmeter, one used AA battery and one
just
off the blister, and both readings were 1.5V
Can you enlighten us?
Carlos
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-
> server@matronics.com] On Behalf Of Eric M. Jones
> Sent: ter=E7a-feira, 9 de Setembro de 2008 15:47
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Electronics 101...Advanced.
>
<emjones@charter.net>
>
> Occasionally I get an inquiry from a customer who is checking out his
electrical
> system and finds what they view as an error--They test solid state
components that
> are supposed to be OFF, or diodes that are supposed to not conduct,
and
they
> measure a voltage on the output. This they think must indicate a
failure.
>
> Usually, I can't figure this out from the description until some
emails or
calls have
> been exchanged, but it always boils down to the following--
>
> The existence of an "output voltage", even a very substantial voltage,
does not
> mean much. If there was a load connected from the output, there would
be
no
> measured voltage (on a standard voltmeter).
>
> Voltmeters always possess a load. Digital types are usually 10
MegOhms,
which is
> small enough to interfere very little with the circuit being measured,
but
for many
> applications can lead to incorrect or puzzling results--for example
measuring dry
> cell batteries, or the output of solid state switches or diodes--In
these
tasks, output
> load is important. (It is trivial to make a voltmeter with GigaOhms or
greater
> resistance but they find little use except in the rare experiment.)
>
> "The problem with the world is that only the intelligent people want
to be
> smarter, and only the good people want to improve."
> - Eolake Stobblehouse
>
> --------
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge, MA 01550
> (508) 764-2072
> emjones@charter.net
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p 3378#203378
>
>
>
>
>
>
>
>
>
>
>
>
>
Message 5
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Subject: | Re: Electronics 101...Advanced. |
> Occasionally I get an inquiry from a customer who is checking out his electrical
system and finds what they view as an error--They test solid state components
that are supposed to be OFF, or diodes that are supposed to not conduct, and
they measure a voltage on the output. This they think must indicate a failure.
>
So a real life example might be someone checking to see if their essential bus
diode is working by measuring voltage using their multimeter. One might find
12-14V at the main bus when the e-bus alternate feed is on and the battery contactor
is off and therefore assume the diode isn't working. Further tests might
reveal that while you might measure a non-zero voltage at the main bus, there
is no current available if one was to try to power a device, such as a light.
Anyone ever have this happen?
--------
Mike Behnke
RV-9A Finish/FFwd
Andover, MN
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 3466#203466
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