Best place to install the Skyview Amp Shunt

[Elmer]

I'm getting ready to install the Amp Shunt. I'm thinking the best place is on the engine side of the firewall, to the 12 volt wire. Then send the EMS wires in to the 37 pin connector. It looks to me that I need to just cut the 12 volt wire that is away from the starter. Place the wire closest the the battery as + and the other cut end as - mounted to the shunt. I'm not sure I have it right so any help will be appreciated.
Thanks

 

[jakej]

On the firewall is what I do, just choose position A,B or C as per install manual.

Jake J

 

[Elmer]

Thanks for the help Jake. I plan to use position C. The way I see it in the manual, I cut the wire and put one end on the shunt and the other end on the other end of the shunt. That will be + on shunt facing battery and - on the other end. Am I seeing this right?
Elmer in Missouri 

 

[jakej]

You are, happy building
Jake J

 

[Elmer]

Thanks again.
Elmer

 

[preacoupe]

If I'm remembering correctly, the "C" position is the preferred setup by a few memebers. Because of my electronic ignorance, is C the common, "standard" location? I don't know enough to know why A or B would be more desirable.

 

[Dynon]

Here are what each method gets you, respectively. I'll let other people speak to why they've chosen their particular install:

A is the classic cessna 172 style ammeter - shows negative while the battery is discharging and positive while it's charging (right after start)

B tells you what you're getting out of alternator to both the battery and loads

C tells you aircraft loads only (no battery)

 

[jakej]

If I'm remembering correctly, the "C" position is the preferred setup by a few memebers.  Because of my electronic ignorance, is C the common, "standard" location?  I don't know enough to know why A or B would be more desirable.

If you want the Alt output I'd use B & if you have the VP-X then it will show the same result as C as well.

HTH

Jake J

 

[mmarien]

As Jake notes, VP-X with the B method shows where the draws are.

In the display below, the battery is drawing 5.3A and the rest of the devices are drawing 17.2A for a total of 23 (22.5) which is what is displayed on the ENGINE page (Method B). Method A would show 5A on the ENGINE page. Method C would show 17A on the ENGINE page.

In the display below without the engine running. Method A would show -4A on the ENGINE page. Method B (shown) and C would show 0A on the ENGINE page.

 

[Elmer]

Thanks for all the help. More questions to come!

 

[vlittle]

Melted Shunt Base

Today, I found my Shunt free-floating under my cowling. The plastic base had melted and the shunt attachment screws had pulled through. It was located more than 10 inches from any exhaust pipe, so I concluded that the plastic base is not the proper material for this application.

I fabricated a new base out of phenolic, and problem solved.

So, my recommendation is that anyone with this shunt.... DO NOT install it firewall forward, especially in tightly cowled environments. Better yet, use the hall-effect sensor.

 

[RVDan]

Some thoughts on the choices.   In my opinion, the most valuable piece of information you need from the amps indication is how much power the alternator is producing (method B). The reason is that the alternator has output limits (rating) and managing load to be less than the rated output is something that enables you to ensure that you are not overloading this important piece of equipment and in fact you can extend the life by keeping the load at less than 60% or so of the rating.  All airplanes with complex electrical systems are set up this way.  The pilot manages electrical loads to keep them within limits. 

If you choose the Cessna method (A) you know whether the alternator is providing an output to match the load (ammeter reads 0), but nothing about how much load you actually have.  It also tells you when the battery is recharging and by how much (+ amps) It will tell you when the alternator fails (- amps), but so will the voltmeter.  If the total electrical loads on the aircraft are well below the alternator limits this method is OK but provides less information.  Aircraft manufacturers often use this method so they don't have to provide a voltmeter to detect alternator failure. 

Method C tells you load without battery recharge so is pretty much useless for anything that I can think of.

I use method B.  The ammeter tells you if you are nearing or exceeding alternator ratings.  When you get to know what the aircraft systems normally draw, tells toy the battery recharge current, and the voltmeter is the primary instrument that tells you if the alternator failed or is failing. 

Hope that helps with some understanding of the advantages of the different methods.

Dan