Today's Message Index:
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1. 07:57 AM - EGT instrument test (Robert L. Nuckolls, III)
2. 09:20 AM - Re: Burning Vans Engine Gauges - Part 3 (JakeTheBosun)
3. 11:49 AM - Re: Re: Burning Vans Engine Gauges - Part 3 (Robert L. Nuckolls, III)
Message 1
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| Subject: | EGT instrument test |
>Comments/Questions: Pete at Westach tells me that if I can apply a
>3.5mv current to the EGT, that it should read 1500f on the
>meter. Do you know where to get something that I can apply such an
>electric voltage. They have a chart for all the different voltages
>and resulting readings, on their web site.
3.5 mV is a bit low for 1500F . . . I think
it's more like 35.0 mV. See:
http://www.omega.com/temperature/Z/pdf/z218-220.pdf
"Applying voltage" to a thermocouple readout is
but a gross test of functionality. Significant
errors can be introduced unless the voltage
is applied with consideration for "parasitic thermocouple
junctions". See:
http://www.aeroelectric.com/articles/excerpt.pdf
Assuming that you're interested in doing a
gross functionality test at 34mV, then you can
craft this little test rig.
Emacs!
A couple of easily acquired resistors from
Radio Shack and a AA battery holder.
http://www.radioshack.com/product/index.jsp?productId 62247
http://www.radioshack.com/product/index.jsp?productId 62338
http://www.radioshack.com/product/index.jsp?productId=2994588
wired as shown will get you a voltage in the
right ball park. If all the errors are accounted
for, your instrument will read 1504F, but if it's
off by as much as 50 degrees, I wouldn't worry
about it.
An accurate calibration test of the instrument
will require more attention to details.
Bob . . .
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( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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Message 2
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| Subject: | Re: Burning Vans Engine Gauges - Part 3 |
Well I spent some time with the ammeter, with and without engine running. There
appeared to be no overheating. There is less than an amp at the instrument buss.
There is less than 4 amps overall at the alternator once it recovers from
start. I even tried banging on the alternator while it was running. All the
grounds and connections have been checked.
....all I am left with is the assumption that the alternator ran away....cooked
the resistors in the gauges, and they finished melting when it was producing
within limits. Also I think that the "starting" draw down is not good.
I plan to change the alternator and instruments. I wonder if anyone has suggestion
about isloating instruments during start cycle?
Thanks!
--------
Jake
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=249534#249534
Message 3
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| Subject: | Re: Burning Vans Engine Gauges - Part 3 |
At 11:19 AM 6/22/2009, you wrote:
><george@yukonflying.com>
>
>Well I spent some time with the ammeter, with and without engine
>running. There appeared to be no overheating. There is less than an
>amp at the instrument buss. There is less than 4 amps overall at
>the alternator once it recovers from start. I even tried banging on
>the alternator while it was running. All the grounds and connections
>have been checked.
>
>....all I am left with is the assumption that the alternator ran
>away....cooked the resistors in the gauges, and they finished
>melting when it was producing within limits. Also I think that the
>"starting" draw down is not good.
>
>I plan to change the alternator and instruments. I wonder if anyone
>has suggestion about isloating instruments during start cycle?
What alternator/regulator combination are you using?
Do you have any form of OV protection? Any OV
event that is even slightly hazardous to aircraft
electro-whizzies is easily managed by appropriate
protection.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
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