---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 09/10/15: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:44 AM - Re: Re: Pitot Heat Ground (Robert L. Nuckolls, III) 2. 06:05 AM - Re: Pitot Heat Ground (Robert L. Nuckolls, III) 3. 06:59 AM - Re: Pitot Heat Ground (Gerry Van Dyk) 4. 08:37 AM - Re: Pitot Heat Ground (Robert L. Nuckolls, III) 5. 08:44 AM - Re: Pitot Heat Ground (Robert L. Nuckolls, III) 6. 02:04 PM - Re: Pitot Heat Ground (Robert L. Nuckolls, III) 7. 04:52 PM - Re: Pitot Heat Ground (Gerald Champagne) ________________________________ Message 1 _____________________________________ Time: 05:44:43 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Pitot Heat Ground > >But I'd hope someone at Dynon could give you the real answer. Agreed. I've had some conversation with Dynon in years past . . . conversations that gave the impression of solid technical competence. Given their successes in this market, your expectations for the quality of their support is not unwarranted. >If the magnetometer is built into the ADAHRS, >you could just prepare for having to remote it >(a few extra wires), and just try it before purchasing the extra magnetometer. > >On Tue, Sep 8, 2015 at 5:37 PM, JDA_BTR ><dudley@jdatkinson.net> wrote: >"JDA_BTR" <dudley@jdatkinson.net> > >It's a good thought.=C2 The ADAHRS location in >the wing is very convenient to the pitot for >AOA.=C2 The magnetometer can be had as a remote unit and put elsewhere. > >Nonetheless I would like to know about the >situation as presented, because I'm curious - >why would the controller box be grounded if it >is so important to carry a ground wire all the >way back to the battery; and when the faqs here >say the ground can be local and simple.=C2 Would >running that wire reduce magnetometer interference even if I ran it? Exactly, that "ground wire directly to the battery" phrase has popped up over the years in several OBAM aviation installation manuals . . . were anyone at King Radio, Collins, Narco or ARC to make such an assertion, the writer should be tasked with a "lunchtime learning session" for colleagues and instructed to "bring us up to date on the physics of your assertion." I would LOVE to be in the audience for THAT one! I'm not clear as to where the all the components are located on the airplane with respect to each other . . . pitot tubes are generally on the wing, the AHRS is out there too? Help me understand . . . Bob . . . ________________________________ Message 2 _____________________________________ Time: 06:05:54 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Pitot Heat Ground At 01:50 PM 9/9/2015, you wrote: >I don't see anything in the dynon installation manual about >connecting directly to the battery. >http://dynonavionics.com/downloads/Install_Guides/Heated_Unheated_AOA_Pitot_Probe_Installation_Guide_-_Rev_C.pdf` >It says: > >Do not connect the Black (Ground) wire to the airframe as a Ground >connection. Doing so will introduce high currents (10A) into the >airframe. This can introduce a significant voltage drop, and >potentially cause engine instrumentation, avionics, and audio system >electrical problems. Good find . . . the author of these words demonstrates a poor understanding of grounding for the purposes of achieving (1) reliable power to the device and (2) minimizing risk of noise propagation to other systems. >Also it says the ground wire should be: >Constant connection to ground (not routed through a switch or fuse / >circuit breaker). Must be sized to conduct 10A with minimal voltage >drop. Ground connection must be constant FOR PITOT HEAT STATUS LINE >(White wire) to operate when the controller is powered Off or not functioning. Just why anyone would run a ground wire through a switch is a mystery . . . It's sad to discover these kinds of muddy thought in the manuals for what should be a no-brainer installation. Those kinds of statement inject what I have dubbed a "divide by zero" factor into the document. Emacs! Whether you're a politician, engineer, philosopher, CEO . . . what ever. Validity of many hours/pages of ideas become suspect when you include the "divide by zero" assertion into your 'formula for success'. Such assertions will at best make the rest of your ideas suspect . . . if not nullify them entirely. It's sort like spending an hour on the phone with tech support before somebody notices that the thing isn't even plugged in . . . I used to have a contact in Dynon management . . . haven't talked in years. I'll see if he's even still there . . . Bob . . . ________________________________ Message 3 _____________________________________ Time: 06:59:04 AM PST US From: Gerry Van Dyk Subject: Re: AeroElectric-List: Pitot Heat Ground Bob=2C perhaps I=27m misunderstanding this thread=2E You said=3A =3E =3E =3E =3E Just why anyone would run a ground wire through a =3E switch is a mystery =2E =2E =2E- =3E =3E It=27s sad to discover these kinds of muddy thoughts =3E in the manuals for what should be a no-brainer =3E installation=2E =3E =3E =3E The quote from the installation manual is=3A =3E =3E =3E =3E =3E =3E Constant connection to ground (NOT routed through a switch or fu se / circuit breaker)=2E =3E =3E =3E =3E Isn=27t the manual telling the installer to bring the ground wire back t o the main ground block=2C presumably the forest-of-tabs on the firewall =3F Why would this manual be cause for concern=3F Gerry ________________________________ Message 4 _____________________________________ Time: 08:37:15 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Pitot Heat Ground >>>Constant connection to ground (NOT routed through a switch or fuse >>>/ circuit breaker). >Isn't the manual telling the installer to bring the ground wire back >to the main ground block, presumably the forest-of-tabs on the >firewall? Why would this manual be cause for concern? Why would such a statement even be necessary? Are there cases in the wild where someone's on-purpose design did take ground through a fuse or switch? The mere mention this would probably bring smiles to the system integrators at Textron but it plant's seeds of an exceedingly poor idea in the minds of their target market . . . the neophyte builder/installer. "Gee, are there instances where ground paths SHOULD go through switches or breakers?" This is why I have always encouraged folks to supply lucid wiring schematics with their products. No pictograms. Schematics are to electronics as numbers and operator symbols to mathematicians. The universal language understanding of how best to assemble something is the annotated schematic . . . like those you see in Appendix Z of the book, diagrams at the back of a Cesnna Service Manual, or the EXCELLENT diagrams published for KIA cars. Those diagrams offer a path for understanding between designers and users. I once spent a couple weeks in CA giving Japanese technicians an overview of a television time base corrector that my company built . . . and I wrote the manual for. Their English was poor, my Japanese nil, but they understood television, waveforms and SCHEMATICS. If an idea can be easily depicted on the wiring diagram, then do it. This completely negates the need for words. If words ARE offered, they should re-enforce the schematic with very low risk for doubt. Words are 'icing' on a an underlying 'cake' that should stand alone on the language of universal symbology and mathematical expression. I would hope the author of the ground wire statement was simply trying to compensate for the lack of lucid illustrations. As we've seen in this thread, vagaries in the use and understanding of language have generated a whole lot of conversation trying to figure out what COULD have been described in a few lines on a page. Unfortunately, other words in the document do not suggest that the author has a good handle on how the various appliances on an airplane can be encouraged to happily co-exist. This may well be an example of a condition common to many tech manufacturers. Marketing hands down goals, engineering designs to the goals, production experts package and manufacture the thing and 'tech writers' put out the books. It's the Silo-Syndrome where good stuff can get blown to the winds as a task is pitched from one silo to the next. Bob . . . ________________________________ Message 5 _____________________________________ Time: 08:44:53 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Pitot Heat Ground At 04:55 PM 9/8/2015, you wrote: >Subject: AeroElectric-List: Pitot Heat Ground >From: "JDA_BTR" >To: aeroelectric-list@matronics.com > > >I read the faqs, and know the recommendation to just take the pitot >ground to the chassis. Let's see if we can zero in on the physics. Is The pitot heat controller in conductive enclosure? Does its ground wire make electrical connection to the enclosure? If the above are both 'yes' then run the power ground to a point on the airframe separate from but in the vicinity of where the controller lives in the airplane. Adding a 'ground wire' off to some other portion of the airplane is of no value. It will simply be a conductor of much higher resistance than the airframe and carry a exceedingly small proportion of pitot heater current. Bob . . . ________________________________ Message 6 _____________________________________ Time: 02:04:04 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Pitot Heat Ground Another 'point of physics' that goes to your question. I just went to the workbench, laid my handy military surplus compass on the bench then held a wire over the needle at the optimal angle to antagonize the readings. With 3A flowing in the wire, I had to lower it to within about 5 inches to detect any movement of the needle. 10A would probably produce noticed motion at 14 inches or so. The interference I noted was 1 degree or less. The most rigorous certification of hardware under DO160 for magnetic effects is 'category Z' which may produce 1 degree of deflection while located 0.3 meters away from the compass . . . or about 12 inches. My 'shade tree' magnetic effects experiment suggests that 12' of separation for a 10A conductor will produce no observable deflections from real magnetic heading. Bob . . . ________________________________ Message 7 _____________________________________ Time: 04:52:32 PM PST US From: Gerald Champagne Subject: Re: AeroElectric-List: Pitot Heat Ground On Thu, Sep 10, 2015 at 4:02 PM, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > > With 3A flowing in the wire, I had to lower > it to within about 5 inches to detect any > movement of the needle. 10A would probably > produce noticed motion at 14 inches or so. > That doesn't sound right. The strength of a magnetic field should increase linearly with current, but should fall off as a function of distance cubed. A 3A current at 5 inches should show the same deflection as a 10A current at about 7.5 inches, not 14 inches. Did I miss something? Gerald ------------------------------------------------------------------------------------- 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.