[Shop-talk] IR temperature meter

[Mark Watson]

Dear All,

    Wow.  Think about  Tony's original statement "which I use around the 
shop checking AC in and out temps, motor temps, etc . ." and look at the 
chart Randall pointed to.

    So when a hot rodder (not me) points his IR thermometer at his polished 
aluminum radiator or polished aluminum thermostat housing he's certainly not 
getting anything like a meaningful measurement is he?  "Aluminum Highly 
Polished" has an emissivity of about .05 versus what Randall claims of 
around .95!

    NOTE: Randall, I'm not doubting on your statement - I have no basis to 
know either way!

    The other thing about IR thermometers is to remember that they don't 
really measure at a fixed size point but see a cone that increases in size 
with distance.  Is there some optimal distance at which to use them?

    And yet another interesting and educational discussion!

Mark Watson
1965 Ford Falcon hopefully short term repair project
1956 Daimler Regency Mk II '104' - in the middle of a slow restoration
plus various other transportation pods

----- Original Message ----- 
From: "Randall" <tr3driver at ca.rr.com>
To: "'Shop Talk List'" <shop-talk at autox.team.net>
Sent: Friday, January 29, 2010 2:08 PM
Subject: Re: [Shop-talk] IR temperature meter


> To put it another way, the accuracy of your meter depends greatly on the
> emissivity of the object it's pointed at.  In theory, to get an accurate
> non-contact measurement, you must know and correct for the emissivity of 
> the
> object of interest.  Some thermometers have an adjustment for this, but 
> most
> inexpensive ones just assume it's around .95 (which is reasonably close 
> for
> most materials).
>
> http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html
>
> But air has a really lousy emissivity and you aren't correcting for it.
>
> -- Randall