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Shunt insulation

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stuart(at)stuarthutchison
Guest

Posted: Sat Apr 28, 2012 7:55 pm Post subject: Shunt insulation

G'day  Bob,

  

 My shunt is mounted  in the 'hot' wire between the live post of the starter contactor (not measuring  start currents) and the main and avionics busses.  The B-lead is  upstream (so to speak - depends whether we're talking electrons or holes  !), so I can read the current into and out of the battery.   I've already 1A fused the signal leads (which go to my EFIS), but I wanted  additional insulation around the shunt to protect from shorts should anything  metalic fall between it and the fuselage during aerobatics.  I don't  really understand how a shunt is calibrated, so I'm wondering if clear  heatshrink and having the shunt on the back of the firewall will alter the  temperature environment of the shunt enough to affect it's calibration?   You may be able to see the heatshrink in the photo ... which has holes punched  for the terminals to screw down.

  

  

Kind regards,  Stu<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office"  /> 

  

F1 Rocket    VH-FLY        http://www.mykitlog.com/RockFLY      [url=about:www.teamrocketaircraft.com]www.teamrocketaircraft.com[/url]

14581m_-_D300_SHUP.jpg

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john.maccallum(at)bigpond
Guest

Posted: Sat Apr 28, 2012 11:26 pm Post subject: Shunt insulation

G’day Stu,

No it won’t be affected by temperature enough to be a problem. A shunt is a low value resistor in series with the circuit you want to measure the current in.

An ammeter is a sensitive volt meter that measure the voltage being dropped across the shunt (resistor).

 

The calibration of the shunt will the depend on the Full scale deflection current required by the Ammeter. 

Needless to say just use the shunt supplied with the engine monitor package and you will be ok.

 

Cheers

 

John MacCallum

VH-DUU

RV10 #41016

 

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Stuart Hutchison

Sent: Sunday, 29 April 2012 1:54 PM

To: aeroelectric-list(at)matronics.com

Subject: Shunt insulation

 

G'day Bob,



 



My shunt is mounted in the 'hot' wire between the live post of the starter contactor (not measuring start currents) and the main and avionics busses.  The B-lead is upstream (so to speak - depends whether we're talking electrons or holes !), so I can read the current into and out of the battery.  I've already 1A fused the signal leads (which go to my EFIS), but I wanted additional insulation around the shunt to protect from shorts should anything metalic fall between it and the fuselage during aerobatics.  I don't really understand how a shunt is calibrated, so I'm wondering if clear heatshrink and having the shunt on the back of the firewall will alter the temperature environment of the shunt enough to affect it's calibration?  You may be able to see the heatshrink in the photo ... which has holes punched for the terminals to screw down.



 



Kind regards, Stu

 

F1 Rocket    VH-FLY       http://www.mykitlog.com/RockFLY      [url=about:www.teamrocketaircraft.com]www.teamrocketaircraft.com[/url]

  [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 29, 2012 4:36 am Post subject: Shunt insulation

At 02:22 AM 4/29/2012, you wrote:

 G’day Stu,



 No it won’t be affected by temperature enough to be a problem. A shunt is a low value resistor in series with the circuit you want to measure the current in. An ammeter is a sensitive volt meter that measure the voltage being dropped across the shunt (resistor).

  

 The calibration of the shunt will the depend on the Full scale deflection current required by the Ammeter. 

 Needless to say just use the shunt supplied with the engine monitor package and you will be ok.

  

 Cheers

  

 John MacCallum

 VH-DUU

 RV10 #41016



  I will expand on John's righteous answer to add that GOOD shunts are made of a strange metal called manganin. This is an alloy of multiple metals designed to give the shunt a zero, or near-zero coefficient of resistance versus temperature. Obviously, a shunt carries current through a resistance which heats it up. Further, shunts may be situated in environmental extremes of temperature.

  It's desirable to have a very low temperature coefficient for resistance so that the instrument reads correctly under all operating extremes.

  Hence, any additional heating that might be attributed to the added insulation is of no consequence.

  I will add also that concerns for loose pieces of metal getting into things electric are probably not well founded. TC aircraft have had many, many examples of exposed, high current conductors go out the production line door. The design goals are better served by making sure things are well bolted down as opposed to insulating the bus bars (etc) from the effects things flying around unrestrained.

  Bob . . .

 

 

 



 

    Bob . . .     [quote][b]

stuart(at)stuarthutchison
Guest

Posted: Sun Apr 29, 2012 5:44 am Post subject: Shunt insulation

Thanks Bob & John.

  

 Excellent ... good news, thank you.

  

 I think my 20 mintues to mitigate the low risk to next  to zero was worth it.  I have seen some incredible collections of  spare washers, swarf and lockwire offcuts etc in the bellies of TC aircraft  .. probably a good thing they're not rolled inverted as often as my Rocket will  be 

  

  

Kind regards,  Stu<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office"  />

  



   From:  owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert  L. Nuckolls, III

Sent: Sunday, April 29, 2012 10:34 PM

To:  aeroelectric-list(at)matronics.com

Subject: RE: Shunt  insulation

 

At 02:22 AM 4/29/2012, you wrote:

Gï¿½day Stu,



No it wonï¿½t be  affected by temperature enough to be a problem. A shunt is a low value resistor  in series with the circuit you want to measure the current in. An ammeter is a  sensitive volt meter that measure the voltage being dropped across the shunt  (resistor).

 

The calibration of the shunt will the depend on the  Full scale deflection current required by the Ammeter. 

Needless to say just  use the shunt supplied with the engine monitor package and you will be  ok.

 

Cheers

 

John MacCallum

VH-DUU

RV10  #41016



    I will expand on John's righteous answer to add that GOOD shunts    are made of a strange metal called manganin. This is an alloy of    multiple metals designed to give the shunt a zero, or near-zero    coefficient of resistance versus temperature. Obviously, a shunt    carries current through a resistance which heats it up. Further,    shunts may be situated in environmental extremes of temperature.

   It's desirable to have a very low temperature coefficient    for resistance so that the instrument reads correctly under all    operating extremes.

   Hence, any additional heating that might be attributed to    the added insulation is of no consequence.

   I will add also that concerns for loose pieces of metal    getting into things electric are probably not well founded.    TC aircraft have had many, many examples of exposed, high    current conductors go out the production line door. The    design goals are better served by making sure things are    well bolted down as opposed to insulating the bus bars    (etc) from the effects things flying around unrestrained.

   Bob . . .





   

     Bob . . . [quote]



href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List

href="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/c

[b]

email(at)jaredyates.com
Guest

Posted: Sun Apr 29, 2012 6:40 am Post subject: Shunt insulation

I shorted mine the other day while trying to install a prop oil line. Note to self, don't forget to disconnect the negative battery lead when waving long metal bits around under the cowl. 



On Apr 29, 2012, at 8:34, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:



[quote]  At 02:22 AM 4/29/2012, you wrote:

 Gï¿½day Stu,



 No it wonï¿½t be affected by temperature enough to be a problem. A shunt is a low value resistor in series with the circuit you want to measure the current in. An ammeter is a sensitive volt meter that measure the voltage being dropped across the shunt (resistor).

  

 The calibration of the shunt will the depend on the Full scale deflection current required by the Ammeter. 

 Needless to say just use the shunt supplied with the engine monitor package and you will be ok.

  

 Cheers

  

 John MacCallum

 VH-DUU

 RV10 #41016



  I will expand on John's righteous answer to add that GOOD shunts are made of a strange metal called manganin. This is an alloy of multiple metals designed to give the shunt a zero, or near-zero coefficient of resistance versus temperature. Obviously, a shunt carries current through a resistance which heats it up. Further, shunts may be situated in environmental extremes of temperature.

  It's desirable to have a very low temperature coefficient for resistance so that the instrument reads correctly under all operating extremes.

  Hence, any additional heating that might be attributed to the added insulation is of no consequence.

  I will add also that concerns for loose pieces of metal getting into things electric are probably not well founded. TC aircraft have had many, many examples of exposed, high current conductors go out the production line door. The design goals are better served by making sure things are well bolted down as opposed to insulating the bus bars (etc) from the effects things flying around unrestrained.

  Bob . . .

 

 

 



 

    Bob . . .      	  Quote: 	
		  



===================================

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

===================================

cs.com

===================================

matronics.com/contribution

===================================



	


[b]

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 29, 2012 8:31 am Post subject: Shunt insulation

At 09:40 AM 4/29/2012, you wrote:

 	  Quote: 	
		  I shorted mine the other day while trying to install a prop oil 

line. Note to self, don't forget to disconnect the negative battery 

lead when waving long metal bits around under the cowl.


	


   How did you have a 'hot' shunt with the battery

   contactor OFF?

   Bob . . .

email(at)jaredyates.com
Guest

Posted: Sun Apr 29, 2012 10:19 am Post subject: Shunt insulation

Thanks for asking Bob, your question inspired me to pull out z13/8

again to make sure I hadn't hooked it up wrong!  If I understand

correctly though, it looks like the shunt for the SD8 goes from the

always-hot side of the battery contactor via a 20AWG fuse link.  Is

that not correct?  It's been a little while since I hooked all of

those wires up.



On Sun, Apr 29, 2012 at 12:28 PM, Robert L. Nuckolls, III

<nuckolls.bob(at)aeroelectric.com> wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>

 At 09:40 AM 4/29/2012, you wrote:

>

> I shorted mine the other day while trying to install a prop oil line. Note

> to self, don't forget to disconnect the negative battery lead when waving

> long metal bits around under the cowl.

  How did you have a 'hot' shunt with the battery

  contactor OFF?



  Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 29, 2012 4:14 pm Post subject: Shunt insulation

At 01:17 PM 4/29/2012, you wrote:

 --> AeroElectric-List message posted by: Jared Yates <email(at)jaredyates.com>



 Thanks for asking Bob, your question inspired me to pull out z13/8

 again to make sure I hadn't hooked it up wrong!  If I understand

 correctly though, it looks like the shunt for the SD8 goes from the

 always-hot side of the battery contactor via a 20AWG fuse link.  Is

 that not correct?  It's been a little while since I hooked all of

 those wires up.



  Oh . . . THAT shunt. Yes, Z-13/8Q does show that sequence of connection which was shuffled around in Revision R when we deleted the "self excitation" feature for the SD-8 and replaced the 20AWG fusible link with a 30A fuse thusly:



 [img]cid:.0[/img]



  But I understand how it came to be on your airplane and it's no really big deal. I wouldn't change it now. But it did strike me strangely and I had to ask. I should probably add a note to Z-13/8 to elaborate on the 30A in-line fuse. The picture I had in my head at the time suggested that leads supplied on the COTS fuse-holder would place the SD-8 control relay close to the battery contactor. The note would speak to this design goal and suggest that the leads not be spliced. In fact, I did mark the upstream lead as being in the 6-inch-or-less category.

  I've just discovered an rather slick, in-line holder for the plastic fuses. It's offered by marine electrical suppliers (among others). It's not only waterproof by virtue of the now ubiquitous bellows gasket but the snap-on cover features a mounting tab. Pretty cool. 

 



  [img]cid:.1[/img]

 

  Is the system still working since the "shorting" event?  It must have been a really short duration event not to take out the fuse. In any case, I'd replace the fuse. "Teasing" events on fuses can be cumulative and your present fuse might have been re-calibrated downward.

 

  If the fuse IS still intact, I'd like to have it. I'm working an accident case where a sequence of fuse-teasing events accumulated over some 15-20 hours of flight before the fuse gave up. It would be interesting to look at your fuse under a microscope to see if it shows signs of teasing. If the fuse is not intact, well . . . that's what fuses do when they are doing what they do best.

    Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 29, 2012 5:10 pm Post subject: Shunt insulation

At 07:55 PM 4/29/2012, you wrote:

In my installation I have a 20AWG fuse link instead of an inline 

fuse.  I haven't had any reason to turn the master on recently so I 

haven't reconnected the battery to see if things are still working.



  Okay, fusible links are VERY robust fuses. They'll take a

  pretty heavy hit without breathing hard.



The battery is a mostly dead PC680 that I've used just for testing 

purposes, so that might have also limited the amount of current 

available.  I got the usual pop and a little spark or two but the 

fuse link didn't seem to smoke.  It's in a bit of that fiberglass 

insulating stuff so perhaps I should pull that back and make sure 

it's all still good.  Should I replace it with a fuse?  That nifty 

inline holder looks a lot like a weatherpack connector.



   You got it. Yeah, if it were my airplane, I'd go

   for the fuse. Simple, fast, inexpensive and continuing

   to evolve . . . sort of like the elegant hammer . . .



   I'll do some poking around to see if I can find a bulk

   source for those fuse-holders. Either B&C or AeroElectric

   should stock that one.



   Bob . . .

gregmchugh

Joined: 03 Apr 2012
Posts: 42

Posted: Mon Apr 30, 2012 8:33 am Post subject: Re: Shunt insulation

Bob,



They sure look like Weather Pack fuse holders maybe from



http://www.whiteproducts.com/



and the Blue Sea version is on Amazon for $9



http://tinyurl.com/7tzcmc2



Greg

nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 01, 2012 5:49 am Post subject: Shunt insulation

At 11:33 AM 4/30/2012, you wrote:

 	  Quote: 	
		  



Bob,



They sure look like Weather Pack fuse holders maybe from



http://www.whiteproducts.com/



and the Blue Sea version is on Amazon for $9



http://tinyurl.com/7tzcmc2


	


   Yes. I've located a bulk distributor and

   will set up and purchasing account with

   them as soon as I can get to it. Thanks!

   Bob . . .

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