Shunt and ammeter?

Mark P.

Visit my builders log at www.ZenithOwner.com
Joined
Apr 21, 2017
Messages
40
Location
Horizon Lakes Airpark, MI
Installing an HDX with UL Power 350iS engine:

Dynon includes a 60 shunt. I know where in the system to wire in the shunt, but where do the two wires coming from the shunt (to the ammeter) connect to the Dynon? I can't find any mention of this in the diagram.

Also, the Aircraft Wiring Handbook (p. 31) indicates that a shunt is not required to "tell if the alternator is working". It says that I can simply look at the voltage.

So, should I install the shunt or just use the voltage? If I can look at the voltage and see if the alternator is working, what's the advantage of installing the shunt?

Thank you!
 

Mark P.

Visit my builders log at www.ZenithOwner.com
Joined
Apr 21, 2017
Messages
40
Location
Horizon Lakes Airpark, MI
Oops I just found the answer to my first question! The ammeter is in the EMS 220 wiring diagram. I was trying to find it in the wrong diagram. :-?
 

dynonsupport

Dynon Technical Support
Staff member
Joined
Mar 23, 2005
Messages
13,226
The use of an ammeter is up to you. Dynon's engine monitoring systems have amps monitoring because it's traditional and expected in aircraft monitoring systems, not because we have a strong defense for their use.

With modern, high accuracy voltmeters, I don't personally see the advantage given all you generally use the ammeter for is understanding if the alternator is working, and the voltmeter is just as good if not better at that. Additionally, you can set alerts on the voltmeter pretty easily, while getting thresholds on an ammeter that are helpful is pretty hard.

I assume amps was more traditionally measured in light GA planes because it was easier to make a +/- 60A ammeter with hardly any accuracy than it was to make a voltmeter that could tell the difference between 12.2V and 12.8V.

Maybe someone else can make a case for where an ammeter is useful (assuming you have voltage monitoring of course)
 

Raymo

I love aviation!
Joined
Apr 25, 2016
Messages
1,043
Location
Richmond Hill, GA
I like having the ammeter because it tells me the load on the system. If the alternator does go down, I know from experience what each switch will add or subtract from the load on the battery.

Those with an essential bus have already done the math and factored the decision into the bus design.
 

mmarien

Murray M.
Joined
Dec 26, 2009
Messages
1,206
Location
Saskatoon SK CAN
I agree with RayInGA. The load tells me something about the system. I developed an intermittent problem with my alternator. I'll have to admit that a voltage drop caused my ECU to issue a warning that Skyview relayed with an audio warning that scared the beegeezes out of me. But it was the drop in AMPS that got my attention when I viewed the logs.

Capture.PNG


The loss of AMPS caused the voltage to drop to battery level which caused the ECU to issue a warning. The drop in voltage would tell me that the alternator is not working but the graph of the AMPs is undeniable. The other blips in the AMPS near the end of the flight are probably radio calls and flap movement. Those would be difficult to detect with just voltage.
 

Robski

Hang on! I've got an idea!
Joined
Nov 29, 2015
Messages
97
I'll have to admit that a voltage drop caused my ECU to issue a warning that Skyview relayed with an audio warning that scared the beegeezes out of me
Why?

No backup battery?

Over-voltage on the other hand...
Don't ask me how I know!
 

mmarien

Murray M.
Joined
Dec 26, 2009
Messages
1,206
Location
Saskatoon SK CAN
Losing the ECU would mean losing the engine so when it gives a warning I perk up. Turns out it was a fried wire (lose connection) between the ANL fuse and the shunt. All fixed now.

FriedConnection.jpg


FriedWire.jpg
 
Top