Measuring lava fountain with IR thermometer

[Gary350z]

Scott from Apau Hawaii Tours in Hawaii uses an IR thermometer to measure the temperature of a lava fountain from a distance of about 1300 feet. The IR thermometer measures about 1500 degrees Fahrenheit. The USGS says the temperature of the lava is about 2,280 degrees Fahrenheit (1,250 degrees Celsius).

https://youtu.be/QfniIwtMuvo?t=433

He has very interesting videos of the volcano eruption in Hawaii:

https://www.youtube.com/channel/UCTemxd6hzdW5Kt3_5jN7IFg

[Brumby]

My limited experience with IR thermometers has shown me that you need to have a full field of view of the radiant surface across the sensor for more accurate readings.  A partially illuminated sensor will read low because (I believe) it will average across the sensor.  To measure something accurately, it would need a peak detect.

Then there is also the question as to whether you would be reading the temperature of the exterior crust or the glowing magma.  The red lava is also going to be cooler than the yellow.


Those with more knowledge please correct me if I'm wrong.

[Brumby]

Impressive viewing, though.

[apis]

I think that is correct Brumby. The IR-thermometer has a lens that focuses light onto a "single pixel" sensor. On my unit, which looks suspiciously similar to the one in the video, the measure area diameter is 1/12 times the distance.

You also need to know the emissivity which depends on both material composition and wavelength. The termometer assumes a black body and a constant value emissivity for the entire spectra which is rarely the case, so you have to calibrate your thermometer for whatever it is you are measuring if you want accurate results.

[Yansi]

Seems I'm not the only one watching what's going on on Hawaii.  Pretty insane and impressive at the same time. We (luckily!) do not get any lava in the central EU. So I am gladly watching from a saaaafe distance through youtube.

[dmills]

The Italians may beg to differ about no lava in the EU, for all that it has not happened recently.....

Regards, Dan.

[apis]

The spanish and portuguese might as well, although I suppose it depends on what you mean by central EU.

[Brumby]

You also need to know the emissivity ...

Doh!   

That is something I did know and left out.

[Yansi]

The Italians may beg to differ about no lava in the EU, for all that it has not happened recently.....

Regards, Dan.

Certainly not as that active as on Hawaii...

[GerryBags]

The Italians may beg to differ about no lava in the EU, for all that it has not happened recently.....

Regards, Dan.

Certainly not as that active as on Hawaii...

Yes, but NOWHERE is as active as Hawaii... and you also have the Vulcan Eifel on the German/Czech R border. 

[Yansi]

There much more of these "so called active" areas in our region. We do even get one spring here nearby where I live with high contents of sulfur, but I'd not make a drama of that, that lava will start pouring from it next week instead of stinky water.

Under the term "volcanically active" I understand a cone that spits or have spit ash/lava in the last decades, not  that it releases just some gasses and splashed lava thousands years ago. 

[Kleinstein]

.......
Yes, but NOWHERE is as active as Hawaii... and you also have the Vulcan Eifel on the German/Czech R border. 

The Vulcan Eifel is in the western part of Germany and not really active anymore - last time was more than 10000 year ago. The area near the /Czech R border is also only marginally active with some gases and hot springs, though its getting more active the last decades.

However hot springs can be there even very long past the last eruption. When I lived in the US, I lived at the edge of an old volcano. There where still a few hot springs, despite the last eruption was some 1.2 million years ago though that was a big one. The same with the Yellowstone area - lots of hot springs but some 700.000 years since last real activity, though the hot springs could be the start of the next one slowly building up.

The lava temperature is not the same everywhere. In the > 1000 C range there is not need for an extra IR thermometer. Just the color of glow is a good indication. Emissivity is rather high in the near IR range. So this is usually not a big deal unless you have clean metallic surfaces.  Over a long range there can be an issue with the air absorbing some of the IR.