VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 02-20-2016, 04:23 PM
DragonflyAero DragonflyAero is offline
 
Join Date: Jan 2013
Location: Greensboro, NC
Posts: 173
Default Where to measure voltage

Where is the best place to measure voltage, or does it matter?

Thanks!
__________________
Bill Vinson
RV-7 Standard Build
http://www.mykitlog.com/users/index....r&project=2226
Reply With Quote
  #2  
Old 02-20-2016, 07:30 PM
cderk's Avatar
cderk cderk is offline
 
Join Date: Sep 2015
Location: Park Ridge, NJ
Posts: 637
Default

The best place to measure voltage for what???
This is a pretty vague question.
__________________
RV10
http://n688cd.wordpress.com
Reply With Quote
  #3  
Old 02-20-2016, 09:03 PM
Ed_Wischmeyer's Avatar
Ed_Wischmeyer Ed_Wischmeyer is offline
 
Join Date: May 2005
Location: Savannah, GA
Posts: 1,301
Default

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."
Reply With Quote
  #4  
Old 02-21-2016, 06:30 AM
DragonflyAero DragonflyAero is offline
 
Join Date: Jan 2013
Location: Greensboro, NC
Posts: 173
Default

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.
__________________
Bill Vinson
RV-7 Standard Build
http://www.mykitlog.com/users/index....r&project=2226
Reply With Quote
  #5  
Old 02-21-2016, 07:28 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,596
Default

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
Reply With Quote
  #6  
Old 02-21-2016, 07:59 AM
DragonflyAero DragonflyAero is offline
 
Join Date: Jan 2013
Location: Greensboro, NC
Posts: 173
Default

Excellent. Thanks Carl!!!
__________________
Bill Vinson
RV-7 Standard Build
http://www.mykitlog.com/users/index....r&project=2226
Reply With Quote
  #7  
Old 02-21-2016, 12:02 PM
RONSIM's Avatar
RONSIM RONSIM is offline
 
Join Date: Feb 2008
Location: Largo, FL
Posts: 1,029
Default 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
__________________
RV-10 Co-built, maintained, flown (sold)
RV-8A Maintained and flown (Sold)
RV-6A Bought and Flying (N177RV), upgrades $$$
IO360, 180HP/CS, AFS 5600T, D10A, G650, G430, G327, ADS-B, VIZ385 AP
Very Happy Contributor
Comm, SMEL, CFII, A&P
Based at KCLW (Clearwater, FL)
Reply With Quote
  #8  
Old 02-21-2016, 12:33 PM
RV6_flyer's Avatar
RV6_flyer RV6_flyer is offline
 
Join Date: Jan 2005
Location: NC25
Posts: 3,507
Default

Quote:
Originally Posted by RONSIM View Post
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
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.
Reply With Quote
  #9  
Old 02-21-2016, 07:10 PM
erich weaver's Avatar
erich weaver erich weaver is offline
 
Join Date: Aug 2006
Location: santa barbara, CA
Posts: 1,682
Default

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
Reply With Quote
  #10  
Old 02-21-2016, 08:30 PM
airguy's Avatar
airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
Default

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.
__________________
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.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:02 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.