Principles of Surface Temperature Measurement

Dr. Bruce Bugbee, president of Apogee Instruments, talks in-depth about the use of research-grade infrared radiometers for conducting high-accuracy, non-contact, surface temperature measurement. In certain applications, using a high-accuracy infrared radiometers is critical for making measurements that are meaningful. In particular, Apogee Instruments IR sensors have been used all over the world for hydrology studies, road-surface monitoring, plant canopy drought stress detection, and several other applications requiring a rugged, highly accurate sensor. To elaborate on one application, Dr. Bugbee, who is also a current professor of crop physiology at Utah State University, discusses their use in crop canopy temperature monitoring in this lecture.
VIDEO CONTENT
00:07 Measuring Surface Temperature-when temperature sensors are used to measure surface temperature only part of the sensor is touching the ground, measuring surface temperature, and the remainder is touching the air, measuring air temperature. This does not give the true surface temperature, which is why we use infrared sensors.
01:55 Applications of Infrared Radiometer - Infrared sensors measure the true radiation coming right from the surface, soil, leaf, or road surface. Apogee infrared radiometers have been used in agriculture for plant canopy stomatal conductance or irrigation scheduling (02:26), to predict snow melt (03:15), and icy road analysis (03:52).
04:15 How Infrared Radiometers Work- Stefan Boltzmann Law Explained: Energy is proportional to temperature, if temperature goes up then energy goes up. This is fundamentally how we tell radiation from a surface, by the energy emitted from it.
06:24 Emissivity - Emissivity ranges from 0 to 1 and is characteristic of the surface.
07:17 Sensor Calibration- To get accuracy we custom calibrate every sensor. The calibration chamber has a blackbody used to calibrate the sensors. It’s a cone shaped cavity that is painted flat black and has an emissivity close to 1.0. The sensor bodies are controlled at one temperature, the targets controlled at another temperature. Apogee’s sensors are specified at plus and minus 0.2 degrees from -20 to 65 C.
12:38 Field of View- It is critical to understand what you are looking at. The field of view (FOV) of your sensor determines the surface area you measure. Apogee sells 4 different FOVs, 3 circular and 1 horizontal aperture. Circular FOVs have half angles of: 22, 18, and 14 degrees. The horizontal FOV has a horizontal half angle of 32 degrees and vertical half angle of 13 degrees. To help determine how to mount your IR sensor and which FOV is needed to properly see your target, Apogee developed the FOV calculator that will show you the surface area the sensor is measuring found at www.apogeeinstruments.com/irr-... (15:32).
16:44 Atmospheric Window - It is important that your sensor does not get interference from the atmosphere and can see right through to the surface. Many lower quality sensors measure atmospheric radiation including water vapor and carbon dioxide. Apogee sensors are calibrated to measure the atmospheric window from 8 to 14 microns, which does not have interference from carbon dioxide or water vapor.
18:11 Measuring Partial Canopy & Stomatal Conductance Example - Covers an example of how to measure a partial plant canopy and angle the sensor to view more of the plant canopy and less background. Conclusion: Canopy temperatures can be used to determine plant canopy water stress and in this example canopy stomatal conductance. There are simple methods to do this, and complex methods are the ones described in the example, where we measure all the parameters and account for all of them. The complex measurements work over a wider range of conditions than the simple measurements.
29:40 Sensor Maintenance - Three things cause problems: 1) Optical path interference. Spiders can make nests inside the window of the sensor. To fix, clean window with a Q-tip. 2) Calcium deposits. Sprinkler irrigation hits the sensor leaving a hard water film on the window. To fix, dip a Q-tip in vinegar and clean the window. 3) Dust and dirt can build up on the window causing errors. To fix, use window cleaning product and a Q-tip. When cleaning the window don’t push too hard because you can scratch the window.
More information at www.apogeeinstruments.com/infr... and www.apogeeinstruments.com/infr....
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More videos on infrared radiometers at • Brief Overview of Infr... .
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[@tomweickmann6414]

Saw this while looking for an owner's manual for my cheap Harbor Freight temp gun. Just a layman here but quite fascinating on the principles. Hats off to you guys who did their math homework years ago!

[@heimannsensor3197]

Great Video to learn the most important things about infrared radiation and non-contact temperature measurements! Absolutely like it!

[@hammadiachour7668]

Great video thank you very much!

[@ADUAquascaping]

Very good video! Thanks

[@bojanab4961]

One of the best presentations ever! Just fix the writing of the letter Sigma, cause it is written differently :) Anyways this video has helped a lot!!! :D Thank you!

[@millejadecabrera4544]

This is a great help, thank you very much!

[@dernhelm]

Brilliant. Thank you.

[@nancyw294]

Great video

[@tuffsensi1196]

Thank you....

[@tuffsensi1196]

Thank you

[@sholagberutaofeeq4393]

Very nice presentation. . .

[@ApogeeInstrumentsInc]

Thanks Sholagberu. We are glad you enjoyed it!

[@nextnext8902]

thank you!

[@maimaganee]

Hello Dr. can one use this experiment on a free-standing wall?. thank you

[@bremlquan]

@Apogee Instruments Inc. So does water on canopy improve transpiration along with stomatal conductance (bottom right @27:31)? And what is described by mol/ms at 27:31, mols of what, any gas particle? Thanks for this information.

[@mariaestrella5337]

Shocks. Thank you lord and thabk you sir. Im doing my thesis related to agriculture and Some of your explanation are so helpful to me. Godbless sir and goodnight. I will play this again tomorrow

[@mikede2331]

What leaf tempreture range is best for cannabis

[@fractalnomics]

Emissivity 6:00

[@akmt123]

Hi, my 2 laser gun, the bottom one has gone off. Any ideas how to check or replace diode? Model HT-817.

[@DasAntiNaziBroetchen]

lmao you people

[@akmt123]

@@DasAntiNaziBroetchen what is IMAO???

[@deven9766]

it means laugh out of my ass bommer

[@smilesmile787]

what wavelength do the sensors emit?

[@DasAntiNaziBroetchen]

See 18:00

[@msakami]

at 12:11, what if we have sun radiation?

[@zhenhuachen6611]

WITH A METAL PART

[@anthonyromano8565]

I had no idea this problem existed.

[@msakami]

at 12:11 of the video, T_measured should be higher than T_surface

[@fractalnomics]

So 'hot' shiny gold, say 400K, radiates giving a temperature of near 0 Kelvin, as it has a e value of near 0. On the other hand high reflective - high albedo - snow has an e value of near 1. Something is either very wrong with emissivity understanding, or quantum mechanics and thermodynamics physics is wrong - where all matter above absolute 0K radiates EM radiation. Physics is right. I have the answer; what is it worth? Radiation theory is incomplete and needs updating.

[@ApogeeInstrumentsInc]

Hi, Blair. Dr Bugbee is at a conference in Amsterdam at the moment. He doesn't actively monitor our KZbin account so I have emailed your comment to him for a reply. I'll post it here when I get it. Thanks.

[@pquic]

@@ApogeeInstrumentsInc any news ?

[@heynando]

effing A