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Where to measure voltage

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.
 
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.
 
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
 
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
 
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.
 
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
 
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.
 
Is there a voltage drop across the shunt? I hope NOT! there should not be more than .1 V drop per connection, .2 for battery terminals in any circuit.....
 
Is there a voltage drop across the shunt? I hope NOT! there should not be more than .1 V drop per connection, .2 for battery terminals in any circuit.....

Yes there is - that's the point of the shunt, it's how they measure the amperage flowing across it - but it's a small voltage drop, at one millivolt per amp. If you are flowing 30 amps through the shunt, the voltage drop across it is .03 volts. For our purposes it really wouldn't matter which side of the shunt you used for a system voltage tap, but on mine I used the battery side of the shunt.
 
Yes there is - that's the point of the shunt, it's how they measure the amperage flowing across it - but it's a small voltage drop, at one millivolt per amp. If you are flowing 30 amps through the shunt, the voltage drop across it is .03 volts. For our purposes it really wouldn't matter which side of the shunt you used for a system voltage tap, but on mine I used the battery side of the shunt.

That is good info, I did not even think about that.......now I need to go back and look at my wiring......
 
Starter?

Greg Does your shunt happen to measure the starter current too? Always wanted to know the inrush at initial rotation. Have heard anywhere from 400Amps to 150Amps.. John
 
Dynon says not to put it inline with the starter, but there are three other locations for the install.
 
No, I don't measure the starter current. I have my shunt set to measure the total current in/out of the battery (other than the starter) to measure a true charge/discharge scenario, after alternator corrections. So if I'm consuming 23 amps of power but the alternator is handling all of it, I'll show 0 amps on the shunt.
 
Starter?

Yep, a Dynon might not like the kickback voltage along with if there
was a loose connection on the shunt with full 14 volts applied to input.
John
 
I do have the shunt to measure amps also. For volts I connected to a miscellaneous buss from the VP-X. Seems the main interest in voltage is to know if the voltage regulator has run amuck so you can shut down the alternator before everything gets fried.
 
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