nuckolls.bob(at)aeroelect
Guest
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 Posted: Mon Jun 22, 2009 6:57 am Post subject: EGT instrument test |
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| Quote: | | 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.
[img]cid:7.1.0.9.0.20090622095230.01220538(at)aeroelectric.com.0[/img]
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 994588
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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