---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 09/08/08: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:33 AM - Re: Ammeter reading oddly (Robert L. Nuckolls, III) 2. 07:33 AM - What did I do wrong? (Fergus Kyle) 3. 07:34 AM - Re: proper cable for engine instrument (Robert L. Nuckolls, III) 4. 08:04 AM - Re: What did I do wrong? (Ron Quillin) 5. 08:06 AM - Re: Ammeter reading oddly (Hinde, Frank George (Corvallis)) 6. 09:37 AM - What did I do wrong? (Fergus Kyle) 7. 07:32 PM - Re: What did I do wrong? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 07:33:59 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Ammeter reading oddly At 09:56 PM 9/7/2008 +0100, you wrote: > > >You probably don't really want to hear this, but Van's gauges aren't the >best quality items on the planet. I have found that the temperature and >pressure gauges are not that accurate (+/- 15%), so no reason why the >ammeter should be any better! I've always found a voltmeter very >comforting to tell the alternator is still at work. > >Regards, Peter I have a Van's battery ammeter which I've confirmed does have a sensitivity to strong RF fields. I disassembled the gage and was pleasantly surprised at the level of technology used in this particular instrument. I'll direct the reader's attention to the suite of photos at: http://aeroelectric.com/Pictures/Instruments/Vans/ In particular, note the potentiometers (blue) in this view . . . http://aeroelectric.com/Pictures/Instruments/Vans/VAM10_05.JPG I suspect these adjustments are included in all the Vans instruments in this style. In general, I found them well assembled and artfully designed. These use a 4-quadrant, moving-magnet motor to drive a pointer. This is the technology of choice in most mechanical instrumentation used throughout the automotive industry. They're inexpensive, rugged and capable of exemplary accuracy. They DO require some signal conditioning electronics and the electronics are subject to the usual snakes and gremlins. Long term drift (calibration stability) and RF susceptibility are the biggest issues. Indeed, the instrument I have exhibits a characteristic I've never seen before in an instrument. A hand-held transceiver waved around the powered up instrument will drive the pointer either direction depending on position of the antenna. See: http://aeroelectric.com/Pictures/Instruments/Vans/VAM10_09.JPG http://aeroelectric.com/Pictures/Instruments/Vans/VAM10_10.JPG Mechanically, I was surprised that they use thru-hole parts . . . this is NOT the most economical way to assemble a complex device in volumes. The largest disappointment was components that stand up on their lead wires. These instruments might be at risk for loosing a component under qualification vibration. Generally speaking, this series of instrument appear to be of good value . . . particularly if they ALL have calibration pots. I can live with long term changes in calibration as long as I can RECALIBRATE as necessary. I hadn't planned to write about these devices until I've solved the RFI problem . . . but I didn't want this thread to move forward without making folks aware of useful details about how they're built. The two potentiometers probably adjust offset (zero) and scale (calibration). They may be interactive meaning that one has to rock back and forth between zero and full-scale readings so that the pots can be set dead-on. Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:33:59 AM PST US From: "Fergus Kyle" Subject: AeroElectric-List: What did I do wrong? Bob, You said: " It's a study in trade offs. If the electrics of Ferg's jumper are higher loss than 4AWG equivalent, how bad is the temperature rise during a cranking event? Keep in mind that the flat strap sheds heat faster than a round, insulated wire. How bad is the voltage drop during a cranking event? We KNOW that the system total loop resistance is significant. See: http://aeroelectric.com/Pictures/Schematics/Voltage_Drop_Study_2.pdf Gee . . . it may well be that the thin brass strip originally proposed might be okay in the grand scheme of things. I mention all this only because the elegant solution considers ALL the ingredients that go into a recipe for success . . . of which getting the math right for deducing equivalency is but one part." Well, I went there, and behold a neat resistance diagram - good stuff...... Did you do this with a "megger"? I remember my mentor (lo those many years) going over all my work with his megger to confirm - I thought - good connections and no shorts. Is that still the routine? Ferg PS: My main purpose in brass was to establish the shape and size while looking for a copper source. ________________________________ Message 3 _____________________________________ Time: 07:34:20 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: proper cable for engine instrument At 08:54 PM 9/7/2008 -0700, you wrote: > >I need to run the cables for the engine monitor. Which is the better cable >to run I want to have at least 20 leads for a 6 cylinder engine with turbo >and fuel flow. I'm thinking to get the G3 from >http://www.insightavionics.com/g3.htm >any suggestion > >Thanks for the advice In the big iron birds, this kind of instrument would be installed using factory bundles of individual wires . . . ESPECIALLY when part of that installation is thermocouple wire. See what the installation manual calls for first. I suspect it will suggest built-up bundles. Use 22759 for the copper, and the good stuff . . . http://www.omega.com/ppt/pptsc.asp?ref=XC_K_TC_WIRE&Nav=temh06 for thermocouples. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 4 _____________________________________ Time: 08:04:44 AM PST US Subject: Re: AeroElectric-List: What did I do wrong? From: Ron Quillin At 07:26 9/8/2008, you wrote: >PS: My main purpose in brass was to establish the shape and size while >looking for a copper source. Try McMaster-Carr. 8964K271 is a 0.125 x 12" Alloy 110 Electronic-Grade Copper for $7.33. Many other sizes available. http://www.mcmaster.com/ Ron Q. ________________________________ Message 5 _____________________________________ Time: 08:06:30 AM PST US From: "Hinde, Frank George (Corvallis)" Subject: RE: AeroElectric-List: Ammeter reading oddly It's the gauge...The fact the ammeter swings high for a few seconds then returns to normal indicates that everything is working normally. Explanation.... You have a battery that spits out hundreds of amps in 3 to 5 second burst to run the starter...Now think of that energy as a tank of water...You sunddenly opened a big valve at the bottom and let a lot of water out...Now the ballvalve opens and it gradually gets topped up by the small filler pipe until its full then the valve closes and then it stops. Well the alternator is is the small filler pipe and the ammeter is measureing the flowrate back into the tank..I mean battery. That few seconds of +20A is the alternator topping the battery off. Now if the ammeter goes to -10A and stays there in flight you got a problem. Realistically ammeters are a bit of a waste of time, My Dynon has one and I never look at it..But I do have an alarm on battery volts..if it drops to 12.5V I get an audible alarm...Then I look at the amps. Frank RV7a IO360 electric fuel pumps only. Now featuring mogas+ 10% ethanol. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Peter Pengilly Sent: Sunday, September 07, 2008 1:56 PM Subject: RE: AeroElectric-List: Ammeter reading oddly --> You probably don't really want to hear this, but Van's gauges aren't the best quality items on the planet. I have found that the temperature and pressure gauges are not that accurate (+/- 15%), so no reason why the ammeter should be any better! I've always found a voltmeter very comforting to tell the alternator is still at work. Regards, Peter -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Neil Clayton Sent: 06 September 2008 22:50 Subject: AeroElectric-List: Ammeter reading oddly When I first start the engine, and then engage the alternator, the Van's ammeter flips over to +20 for a few seconds. Then it gradually descends to zero and settles a needle's width on the -ve side of zero, where it sits for the duration. If I turn the alternator off, the ammeter goes to -10 so I know it's sensing something, but the slight -ve reading in flight bothers me. Do you think it's just an adjustment issue on the gauge, or is something else going on? Thanks for ideas. Neil ________________________________ Message 6 _____________________________________ Time: 09:37:54 AM PST US From: "Fergus Kyle" Subject: AeroElectric-List: What did I do wrong? Cheers, At the risk of flogging this dog of a topic, I consulted an old friend, "Handbook of Applied Mathematics" in stumbling through several attempts to assimilate Ron's excellent application. I quote: "Wires are often grouped in smaller ropes for ease of use. The group of wires is called a "strand"; the term "wire" being reserved for the individual wires of the strand. Strands are usually built of wires of such a size that the cross-section of the metal in the strand is the same as the cross-section of the solid wire having the same gage (sic) number." This book also gave me a value of 204 mils in diam. Half that, squared, times pi, gave me 32781 square mils. Divide by a thickness of 125 mils gives 261-odd mils or =BC inch. So, .25 by .125 inches seems correct but 1/16 by =BD inch seems easier, in copper. I must remember pie are round, cake are square. Ferg ________________________________ Message 7 _____________________________________ Time: 07:32:10 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: What did I do wrong? At 10:26 AM 9/8/2008 -0400, you wrote: >Bob, > You said: >" It's a study in trade offs. If the electrics of Ferg's jumper > are higher loss than 4AWG equivalent, how bad is the temperature > rise during a cranking event? Keep in mind that the flat strap > sheds heat faster than a round, insulated wire. How bad is > the voltage drop during a cranking event? We KNOW that the > system total loop resistance is significant. See: >http://aeroelectric.com/Pictures/Schematics/Voltage_Drop_Study_2.pdf > Gee . . . it may well be that the thin brass strip originally > proposed might be okay in the grand scheme of things. > I mention all this only because the elegant solution > considers ALL the ingredients that go into a recipe for > success . . . of which getting the math right for deducing > equivalency is but one part." > Well, I went there, and behold a neat resistance diagram - good >stuff...... Did you do this with a "megger"? I remember my mentor (lo >those many years) going over all my work with his megger to confirm - I >thought - good connections and no shorts. Is that still the routine? >Ferg A 'megger' is what the name implies, a meg-ohmmeter usually with a capability of reading thousands of meg ohms. This device would be used to measure insulation resistance while powered up at hundreds if not 1000 volts. The diagram was a hypothetical based on experiences. Although there are micro-ohmmeters that can be used to measure very small resistances directly. The one I have is like this http://www.avtron.com/pdf/ate/t477w.pdf While the 'megger' uses very high voltage to detect and quantify very large resistances the micro-ohmmeter or bonding meter uses high currents to detect and quantify very low resistances. >PS: My main purpose in brass was to establish the shape and size while >looking for a copper source. Did we get you covered? There was a lot of 'stuff' flying around there for awhile. 4awg is 0.2 dia, 0.1 radius. 0.1(squared) x 3.14 or 0.031 square inches cross section. This means that a .032" piece 1" wide copper has the same cross section and conductivity. I may have some .032" or 22 gage (.025") sheet stock in M.L. I'll check tomorrow when I'm there. 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