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That would be 0.6 to 1.4 micrometers, not millimeters. Near IR is in the micrometer wavelength range. Our printed info shows the micro sign correctly; I'm not sure where you grabbed that text, but it is a common formatting error to replace a mu with an m when text is copied and pasted.
There are several ways to do IR thermometry, as you have probably read on perusing the Omega web site: http://www.omega.com/prodinfo/infraredthermometer.html
The Vernier unit is made by Omega, and I confess to not knowing the details of its operation. I think, but do not know, that it functions with a single detector in a cavity that is brought into IR light equilibrium with the target surface--then knowing the IR radiation and the local temperature, the temp of the remote surface can be inferred. I didn't supervise this project, and so don't have good contacts at Omega to get more information. I'll see what I can do.
The Fresnel lens is useful simply because you can get a short focal length with very little lens material.
--
John Gastineau
Staff Scientist and Partner
Vernier Software & Technology
jgastineau@vernier.com
Bernard Cleyet wrote:
John!
1. A minor nit: you mean nm not mm? And 0.6 => 1.4 nm?
2. A single detector?
3. How does it measure the spectral distrib. w/ a single element and no dispersive element?
"To measure temperature, this sensor gathers infrared radiation in the 6 to 14 mm [1] wavelength range. A Fresnel lens on the front of the sensor focuses the radiation onto the sensing element [2]. The observed spectral distribution is used to determine the object’s temperature assuming standard blackbody radiation with an emissivity of 0.95."
bc, who wonders why a Fresnel instead of an ordinary and the material of the lens, etc.
John Gastineau wrote:
What specifically is your question regarding our description?cut
--
John Gastineau
Staff Scientist and Partner
Vernier Software & Technology
jgastineau@vernier.com
Bernard Cleyet wrote:
A few problems w/ this description from Vernier.
How the Infrared Thermometer Works and Measurement Tips
All objects emit infrared radiation, and the amount emitted is proportional to the
object’s temperature and its ability to emit infrared radiation. This ability called
emissivity is based on the material of the object and its surface finish. Emissivity
values range from 0.10 to 1.00 for a perfect black body. (See the chart below.) This
sensor makes its measurement based on a fixed emissivity of 0.95 which covers most
everyday objects. This sensor and all other infrared thermometers do not accurately
measure the temperature of shiny substances, e.g., polished metals, etc. To measure