---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 09/09/08: 5 ---------------------------------------------------------- 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 _____________________________________ Time: 06:00:10 AM PST US From: Steve Stearns Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 07:48:34 AM PST US Subject: AeroElectric-List: Electronics 101...Advanced. From: "Eric M. Jones" 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 _____________________________________ Time: 11:20:59 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 02:36:28 PM PST US From: "Carlos Trigo" Subject: RE: AeroElectric-List: 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. > > > 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 _____________________________________ Time: 05:20:52 PM PST US Subject: AeroElectric-List: Re: Electronics 101...Advanced. From: "MTBehnke" > 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 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.