Today's Message Index:
----------------------
1. 09:18 AM - Shunt Questions (Valovich, Paul)
2. 09:45 AM - Re: Shunt Questions (Daniel Hooper)
3. 10:11 AM - Re: Shunt Questions (Jeff Luckey)
4. 12:33 PM - Re: Shunt Questions (Robert L. Nuckolls, III)
5. 04:08 PM - Re: Shunt Questions (Vern Little)
Message 1
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RV-8A, 420 total hours. Electrical design based on Z13/8 architecture. AFS
4500 EFIS taking ammeter current readings from 50 MV / 60 amp shunt.
Ammeter reading suddenly became very intermittent - mostly inop. Replaced w
ires, D-sub pins, connectors. Extensive troubleshooting with Advanced Fligh
t Systems has led to questions about whether shunt is working properly.
How does one troubleshoot a shunt? No moving parts; no visible damage; All
other electrical systems operating normally.
Paul Valovich
Ridgecrest, CA
N192NM
Message 2
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| Subject: | Re: Shunt Questions |
Could you hook it up temporarily to a good quality volt meter (at the remote
end)?
That could help eliminate some things.
Daniel Hooper
> On Aug 9, 2014, at 11:16 AM, "Valovich, Paul" <pvalovich@dcscorp.com> wrot
e:
>
> RV-8A, 420 total hours. Electrical design based on Z13/8 architecture. AFS
4500 EFIS taking ammeter current readings from 50 MV / 60 amp shunt.
>
> Ammeter reading suddenly became very intermittent =93 mostly inop. R
eplaced wires, D-sub pins, connectors. Extensive troubleshooting with Advanc
ed Flight Systems has led to questions about whether shunt is working proper
ly.
>
> How does one troubleshoot a shunt? No moving parts; no visible damage; All
other electrical systems operating normally.
> Paul Valovich
> Ridgecrest, CA
> N192NM
>
>
>
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=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
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D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3
D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>
Message 3
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| Subject: | Re: Shunt Questions |
=0AHow does one troubleshoot a shunt? =0A=0A=0AGreat question - shunts are
about as "solid-state" as they come.=0A=0ABased on you conversations w/ Adv
anced, we assume that it's not =0Asomething in their system.=C2- Have you
tried swapping-in a known-good =0Ashunt?=0A=0AAs you may already know, a s
hunt is really just a highly-calibrated, very low-resistance resistor.=C2
- On many shunts the main element is soldered between the connection post
s.=C2- I'm wondering if there is some kind of mechanical problem in there
somewhere.=C2- I assume there are no visible cracks or other damage.=0A
=0A=0ATo test a shunt you could:=0A=0A1.=C2- hook-up a test circuit (on t
he bench) with a battery and some small load - maybe a couple of automotive
brake lights (or equivalent).=C2- You want a load of around 5 amps for t
his test.=0A=0A2. Hook-up a DVM to the shunt on the mili-volt scale.=C2-
Your shunt you should be reading just about 1 mV per Amp of current in the
circuit. (technically that's 5/6 mV per Amp, but that's really splitting ha
irs)=0A=0A3. While the circuit is on, agitate the shunt: bang in on the ben
ch top or hit it w/ a plastic mallet and see if the reading remains steady.
=C2- Perhaps some part of the shunt is damaged/cracked and it is having i
ntermittent connection problems. (you will want to have good solid connecti
ons on the shunt terminals for this test - alligator clips probably won't d
o it)=0A=0A4. It would be fun to test w/ high load, something like 40-50 am
ps, but I can't think of an easy way to create a load like that - maybe oth
er Listers have some ideas...=0A=0A=0AGood Luck & keep us posted,=0A=0A-Jef
f=0A=0A=0A=0A=0A=0A=0AOn Saturday, August 9, 2014 9:28 AM, "Valovich, Paul"
<pvalovich@dcscorp.com> wrote:=0A =0A=0A=0A =0ARV-8A, 420 total hours. Ele
ctrical design based on Z13/8 architecture. AFS 4500 EFIS taking ammeter cu
rrent readings from 50 MV / 60 amp shunt.=0A=C2-=0AAmmeter reading sudden
ly became very intermittent =93 mostly inop. Replaced wires, D-sub pi
ns, connectors. Extensive troubleshooting with Advanced Flight Systems has
led to questions about whether shunt is working properly.=0A=C2-=0AHow do
es one troubleshoot a shunt? No moving parts; no visible damage; All other
electrical systems operating normally. =0APaul Valovich=0ARidgecrest, CA=0A
======================
Message 4
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| Subject: | Re: Shunt Questions |
At 12:10 PM 8/9/2014, you wrote:
>How does one troubleshoot a shunt?
>
>Great question - shunts are about as "solid-state" as they come.
>
>Based on you conversations w/ Advanced, we assume that it's not
>something in their system. Have you tried swapping-in a known-good shunt?
>
>As you may already know, a shunt is really just a highly-calibrated,
>very low-resistance resistor. On many shunts the main element is
>soldered between the connection posts. I'm wondering if there is
>some kind of mechanical problem in there somewhere. I assume there
>are no visible cracks or other damage.
The only shunts I've seen 'fail' were
destroyed by gross over-current. If the thing
is not discolored and the screws are tight,
it's good.
Bob . . .
Message 5
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| Subject: | Re: Shunt Questions |
I destroyed a Dynon supplied shunt because the plastic base melted. It was located
FWF.
The fix was to fabricate a new base out of Bakelite. I remember the day when they
were all made that way...
Vern
===================================================
Sent from my iThing. It is responsible for all gramma and typo terrors.
> On Aug 9, 2014, at 12:32 PM, "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
wrote:
>
>
> At 12:10 PM 8/9/2014, you wrote:
>
>> How does one troubleshoot a shunt?
>>
>> Great question - shunts are about as "solid-state" as they come.
>>
>> Based on you conversations w/ Advanced, we assume that it's not something in
their system. Have you tried swapping-in a known-good shunt?
>>
>> As you may already know, a shunt is really just a highly-calibrated, very low-resistance
resistor. On many shunts the main element is soldered between the
connection posts. I'm wondering if there is some kind of mechanical problem
in there somewhere. I assume there are no visible cracks or other damage.
>
> The only shunts I've seen 'fail' were
> destroyed by gross over-current. If the thing
> is not discolored and the screws are tight,
> it's good.
>
>
>
> Bob . . .
>
>
>
>
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