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02-20-2016, 04:23 PM
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Join Date: Jan 2013
Location: Greensboro, NC
Posts: 173
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Where to measure voltage
Where is the best place to measure voltage, or does it matter?
Thanks!
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02-20-2016, 07:30 PM
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Join Date: Sep 2015
Location: Park Ridge, NJ
Posts: 637
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The best place to measure voltage for what???
This is a pretty vague question.
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02-20-2016, 09:03 PM
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Join Date: May 2005
Location: Savannah, GA
Posts: 1,301
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If you measure bus voltage, that may not give you accurate battery voltage before you start. I wish mine was wired to let you measure either.
__________________
RV-9A at KSAV (Savannah, GA; dual G3X Touch with autopilot, GTN650, GTX330ES, GDL52 ADSB-In)
Previously RV-4, RV-8, RV-8A, AirCam, Cessna 175
ATP CFII PhD, so I have no excuses when I screw up
2020 dues slightly overpaid
Retired - "They used to pay me to be good, now I'm good for nothing."
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02-21-2016, 06:30 AM
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Join Date: Jan 2013
Location: Greensboro, NC
Posts: 173
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Sorry for being vague. I am using Dynon Skyview and wanted to know where I should attach the wire that provides the voltmeter reading. I can easily tie into a buss from the VP-X inside the cockpit, or do I need to go back to the engine side of the firewall and connect to the battery or somewhere else? I would think voltage would be the same as long as it is being picked up on the positive side of any device.
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02-21-2016, 07:28 AM
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Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,596
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I offer you may be over thinking this.
Voltage is an excellent measurement for the health of your electrical system. As example, a loss of alternator will immediately be reflected in a signification buss voltage drop.
You will, under some circumstances, get slightly different voltage readings depending on where you measure. The obvious example is the voltage at the battery will be higher than the voltage at the starter when cranking the engine. But - when not cranking the engine the current draw from the battery will not be large enough to make a meaningful difference in voltage between these two points.
Bottom line - connect to a convenient spot on your main buss. This way you are monitoring your panel voltage, and all the elements in play to get the panel that power (battery, alternator, master solenoid, etc.). Whatever small difference in voltage between these elements is not relevant to why you are monitoring system voltage.
Carl
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02-21-2016, 07:59 AM
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Join Date: Jan 2013
Location: Greensboro, NC
Posts: 173
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Excellent. Thanks Carl!!!
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02-21-2016, 12:02 PM
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Join Date: Feb 2008
Location: Largo, FL
Posts: 1,029
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Dynon reads about 0.5 volts low
My Dynon EMS 120 reads the buss voltage about a half volt low, consistently. I have verified this several times with appropriate meters. It is no big deal, and I allow for it in my "tolerance" level.
Ron
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RV-10 Co-built, maintained, flown (sold)
RV-8A Maintained and flown (Sold)
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IO360, 180HP/CS, AFS 5600T, D10A, G650, G430, G327, ADS-B, VIZ385 AP
Very Happy Contributor
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Based at KCLW (Clearwater, FL)
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02-21-2016, 12:33 PM
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Join Date: Jan 2005
Location: NC25
Posts: 3,507
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Quote:
Originally Posted by RONSIM
My Dynon EMS 120 reads the buss voltage about a half volt low, consistently. I have verified this several times with appropriate meters. It is no big deal, and I allow for it in my "tolerance" level.
Ron
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My EMS D10 also is exactly 0.4 Volts low. Dynon replaced the 1st unit I had under warrantee. The 1st unit would read correctly but the replacement is 0.4 Volts low.
If only there were a user calibration adjust point or menu that the user could calibrate and adjust errors out.
__________________
Gary A. Sobek
NC25 RV-6 Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012
To most people, the sky is the limit.
To those who love aviation, the sky is home.
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02-21-2016, 07:10 PM
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Join Date: Aug 2006
Location: santa barbara, CA
Posts: 1,682
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Not a Dynon expert but my understanding on the GRT units is that they read about 1/2 volt low because of an internal diode to stop power from ever flowing backwards out of the unit (from a secondary power input outthrough the primary power input). The diode results in the loss of about 0.5 volts. Maybe same deal in Dynon?
Erich
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02-21-2016, 08:30 PM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
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Most of us with full monitoring want to also check the amps flowing in/out of the battery with a shunt device, which takes two wires (upstream and downstream of the shunt) to measure the amps flowing through the shunt. You can use the battery side of the shunt to also measure your battery voltage. The Dynon EMS does not automatically do this (though I think it really should) so you'll need to split that sampling point to two different pins on the EMS connection.
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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