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Reverse flow in Shunt and Hall Effect

 
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Speedy11(at)aol.com
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PostPosted: Wed Jun 10, 2009 9:22 am    Post subject: Reverse flow in Shunt and Hall Effect Reply with quote

I have a HE device on the B lead from the Alternator to the main battery. It is oriented so that current is measured from the alternator to the main battery thus indicating the load imposed on the alternator.

I have a shunt on the standby battery to measure current being used from the battery.

If current flows in the opposite direction from the planned flow, does one get a negative amperage indication?

Stan Sutterfield
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nuckolls.bob(at)aeroelect
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PostPosted: Wed Jun 10, 2009 6:51 pm    Post subject: Reverse flow in Shunt and Hall Effect Reply with quote

At 12:15 PM 6/10/2009, you wrote:
Quote:
I have a HE device on the B lead from the Alternator to the main battery. It is oriented so that current is measured from the alternator to the main battery thus indicating the load imposed on the alternator.

I have a shunt on the standby battery to measure current being used from the battery.

If current flows in the opposite direction from the planned flow, does one get a negative amperage indication?

Stan Sutterfield

Probably. But it's dependent upon the display
software. I've never encountered a system that
wouldn't show both +/- indications accurately but that
doesn't mean they don't exist. Chances are your
indicator will show a value for both charge
and discharge currents just fine.


Bob . . .

---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------

[quote][b]


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mprather(at)spro.net
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PostPosted: Wed Jun 10, 2009 7:22 pm    Post subject: Reverse flow in Shunt and Hall Effect Reply with quote

Yes.. Current going the opposite direction through the shunt will
generate a negative voltage. The sensor connected to the shunt should
interpret/display that as a negative current.

One other thought is that a large discharge current is created by
operating the engine starter which will generate a significant negative
voltage across the shunt. If using a mechanical display it will slap the
needle around pretty hard. Maybe not a big deal, but something to
consider. One might install a normally-closed relay in the lead to the
shunt which. Connect the controlling coil to the starter switch so that
when the starter is engaged, the meter is disabled. I wouldn't think a
digital display input would have any problems.

If the shunt drops 50mV at full scale alternator output (not an unusual
scheme). Alternator output might be 50A, and starter current might be
250A, so the shunt might drop 500mV (-0.5V) when operating the starter.
Round numbers.
Regards,

Matt-

Quote:
I have a HE device on the B lead from the Alternator to the main battery.
It is oriented so that current is measured from the alternator to the
main
battery thus indicating the load imposed on the alternator.

I have a shunt on the standby battery to measure current being used from
the battery.

If current flows in the opposite direction from the planned flow, does one
get a negative amperage indication?

Stan Sutterfield
**************Dell Inspiron 15 Laptop: Now in 6 vibrant colors! Shop
Dell’s
full line of laptops.
=http:%2F%2Fad.doubleclick.net%2Fclk%3B215566094%3B3786435
8%3Bv)



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Speedy11(at)aol.com
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PostPosted: Thu Jun 11, 2009 6:11 am    Post subject: Reverse flow in Shunt and Hall Effect Reply with quote

Matt and Bob,
Thanks for your responses. You've confirmed my understanding of shunt and HE functions.
I'm using an Advanced Flt Systems AF-3400 and it reads both devices.  I've had external power (regulated power supply) connected to one battery and I was getting negative amp indications. So, with the power supply connected to the battery and electrical consumers turned on, the shunt/HE will show a negative amperage.
I'll be running the engine again in a few days and I'll check to make sure amps are positive with normal alternator operation.
Stan

Quote:
Yes.. Current going the opposite direction through the shunt will
generate a negative voltage. The sensor connected to the shunt should
interpret/display that as a negative current.



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JohnInReno



Joined: 08 Sep 2007
Posts: 150

PostPosted: Thu Jun 11, 2009 8:25 am    Post subject: Reverse flow in Shunt and Hall Effect Reply with quote

Speedy11(at)aol.com (Speedy11(at)aol.com) wrote:
Quote:
I'm using an Advanced Flt Systems AF-3400 and it reads both devices. I've had external power (regulated power supply) connected to one battery and I was getting negative amp indications. So, with the power supply connected to the battery and electrical consumers turned on, the shunt/HE will show a negative amperage.

I am just starting the wiring on my AFS 3500 so I am probably confused, but I thought the shunt and Hall Effect were mutually exclusive. I plan to run both alternators (Z13/Cool through the HE as shown on page 42 of the AF3500 System Manual V5.3. Am I missing something?

John Morgensen
RV9A - wiring
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RV-9A - Born on July 3, 2013
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Bret Smith



Joined: 09 Jan 2006
Posts: 178
Location: Mineral Bluff, GA

PostPosted: Thu Jun 11, 2009 9:17 am    Post subject: Reverse flow in Shunt and Hall Effect Reply with quote

I'm wired for 13/8 and use the AFS3500's. I went with two shunts; one FWF for the main alt and another cabin-side for the SD-8. I had the main alt shunt reading negatively at first and only had to reverse the wires to the AFS unit.

HTH

Bret Smith
RV-9A N16BL
Blue Ridge, GA
www.FlightInnovations.com
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andrewbutler(at)ireland.c
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PostPosted: Fri Jun 12, 2009 8:54 am    Post subject: Reverse flow in Shunt and Hall Effect Reply with quote

Hi John,

When I received my 3500, I received only the Hall Effect sensor that I ordered extra. I have two power supplies and looking at the manual I figured that the both must go through the HE sensor (there are two wires in the photograph and there was no shunt in the box). Just to make sure I contacted AFS. They said that each power supply should be measured separately, and that the shunt was left out by mistake. They shipped it the same day.

I installed the shunt for the main alt firewall forward (Z13/Cool, with the HE sensor for my SD-8 placed behind the panel just in front of the firewall. Haven't fired up the engine yet though.

Andrew
RV7, EI-EEO
Galway, Ireland.

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