[Vwdiesel] OT: remote diagnosis

[Val Christian]

Black paint works on lots of things, but it will raise the emmisivity
above 0.95, which is the default for the consumer devices.  Most of 
the time, it's just not a factor.  

I could do the calculations, but I suspect that the measured temp
of an Al cylinder head would not be more than just a couple of
degrees off from the measurement of a black coolant hose.  Therefore
for most applications having a fixed e is just fine. 

Where absolute temps make a difference, like phase change points, then
getting all the parameters aligned so that you get good measurements 
helps.  For example, checking for freezing lines, liquids boiling, etc.
There are also some measurements where phase change temps are offset, 
like ice rink temperature (hockey needs one temp, figure skating
another) (different skate geometry, and therefore, different pressures;
also different ice performance expectations).

These thermometers are very useful.  I've even used them to measure
cloud temps prior to flight.  On a layered day, it gives you an idea as
to where the freezing levels are.

Someday the devices will be small enough to be a key FOB, and then 
I'll have to buy another.

Val

ps: no need for the Rust-o-leum gas grill paint on the neighborhood
kid..his skin is close to 0.95.  But the skin will be cooler.  Shoot
him in the back of the throat, and add a degree or so, for an approximation.


> 
> 
> I always wanted to find the one which melted Limburger cheese the
> slowest.
> 
> Val
> 
> __________
> LOL!!!
> 
> You aren't far off Val.  Old mechanic's trick on diesel engines is to put a
> gob of lubriplate engine assembly grease on each exhaust runner.  The one
> that wouldn't melt the grease and trickle away was the bad hole.
> 
> Nice to hear of the accuracy of the IR thermometers.  I use mine primarily
> for tire temps on the race car, but there are a myriad of tasks from setting
> the infloor heat loop flow rate in our house, to diagnosing glow plug
> function.   So would it be correct to assume that the correct emissivity
> could be attained by painting everything before you take a reading?  You
> know, shiny metal surface give it a whoosh of black spray paint, then test
> when dry; seems like the neighbor's kid has a fever when over at the shop,
> little diagnostic whoosh of some skin tone spray bomb, and you get an
> accurate reading?  that sort of thing?
> -james
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