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Two shunts on one amperometer

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gz(at)comgz.com
Guest

Posted: Thu Oct 12, 2006 12:51 am Post subject: Two shunts on one amperometer

Hi all,



As I'm not decided where is the best place to connect the shunt of my

amperometer, I was considering to use two shunts: one on the 

alternator output and the other checking all the electrical loads 

(except starter).

The two shunts would go to the gauge through a a S700-2-3 ON-ON double pole

switch.

The advantage would be to be able to check alt output and, in case of alt

failure, check the battery depletion rate.

Any comment or criticism from the experts?



Gianni Zuliani

Tel/Fax +41 91 9710850

Mobile +41 79 3373439

Long-Ez >> Stag-Ez >> Stag-EzR

http://www.comgz.com/tristar.htm

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nuckollsr(at)cox.net
Guest

Posted: Thu Oct 12, 2006 3:29 am Post subject: Two shunts on one amperometer

At 10:44 AM 10/12/2006 +0200, you wrote:



 	  Quote: 	
		  



Hi all,



As I'm not decided where is the best place to connect the shunt of my

amperometer, I was considering to use two shunts: one on the

alternator output and the other checking all the electrical loads

(except starter).

The two shunts would go to the gauge through a a S700-2-3 ON-ON double pole

switch.

The advantage would be to be able to check alt output and, in case of alt

failure, check the battery depletion rate.

Any comment or criticism from the experts?


	


     Measuring the battery depletion rate for alternator-out

     operations by installing n ammeter suggests that you're

     not planning to control battery life by a combination of



     (1) choosing a battery capacity sufficient to operate

     KNOWN loads for what ever duration you choose as part

     of your design for alternator-out operations (Plan-B).



     (2) maintaining the battery with either periodic

     capacity tests or preventative maintenance by replacement

     so that conditions under Plan-B are satisfied.



     The point is that KNOWING battery loads "right now"

     is useless if you don't know what the battery's capacity

     is. Further, planning to do any kind of mathematical

     gymnastics in flight so as to pick-and-choose from

     electrical items you're not going to turn off is

     poor design . . . it distracts from your duties

     as pilot while you fuss with systems analysis

     under duress while in flight.



     The most useful instrument under battery-only

     operations is the voltmeter, not the ammeter . . .

     and then only to tell you whether your planning

     and maintenance efforts have paid off. If the

     battery drops below 11.0 volts sooner than you've

     predicted, then you know you've blown the design

     goal for achieving and maintaining a PREDICABLE

     level of performance under battery-only operations.

        Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

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klehman(at)albedo.net
Guest

Posted: Thu Oct 12, 2006 4:14 am Post subject: Two shunts on one amperometer

Seems like extra work and expense for little gain Gianni.

With a shunt on the alternator you can quickly become familiar with the 

current draw of various items. After an alternator failure it is very 

unlikely that you can manage the current draw for any specific battery 

life unless you have a brand new, tested, fully charged battery at room 

temperature, and have a second pilot to fly the plane while you fiddle 

with it. Just turn everything off that is not needed and revert to a 

previous plan that probably entails use of an E-bus.

Ken L.



Gianni Zuliani wrote:



 	  Quote: 	
		  



Hi all,



As I'm not decided where is the best place to connect the shunt of my

amperometer, I was considering to use two shunts: one on the 

alternator output and the other checking all the electrical loads 

(except starter).

The two shunts would go to the gauge through a a S700-2-3 ON-ON double pole

switch.

The advantage would be to be able to check alt output and, in case of alt

failure, check the battery depletion rate.

Any comment or criticism from the experts?



Gianni Zuliani

Tel/Fax +41 91 9710850

Mobile +41 79 3373439

Long-Ez >> Stag-Ez >> Stag-EzR

http://www.comgz.com/tristar.htm

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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