Opinions? IR laser temperature gauges in the ~ $10-$20 range

Got one. It looks tgtbt, but for $3 bucks I'll try anything.
I wanted two of them, one for the shop and one for the house, but I got the last one. Returns are accepted, shipped from California

I like the specs
Low battery indicator: Warns you when the batteries are dying
Auto shut-off: Turns device off after 10-seconds of inactivity
Backlight display: Makes it easy to use during the day or at night.
Measures in Fahrenheit and Celsius: From -58℉ - 716℉ (-32℃ - 380℃)
Emissivity: Adjustable from 0.1 - 0.99 (Emissivity table included in instruction manual)
Temperature Range: -50 to 380℃ (-58 to 716F)
Accuracy: ±1.5% or ±1.5℃
Resolution: 0.1℃ or 0.1F
Repeatability: 1% of reading or 1℃
Response Time: 500mSec, 95% response
Spectral Response: 8-14 um
Emissivity: 0.95 preset
Distance to Spot Size: 12 : 1
Operating Temperature: 0 ~ 40℃ (32 ~ 104F)
Operating humidity: 10 ~ 95 % R.H.
Storage Temperature: -20 ~ 60℃ (-4 ~ 140F)
Power Supply: 1.5V AAA*2PCS Batteries ( Not included)

Effective for _RELATIVE_ temperature, less effective if the actual number is precisely required. The thermometer is affected by the environment temperature, and the entire device needs to equalize to the temperature of where it is used. If the environment is a different temperature the reading will be different even if the temperature measured is carefully controlled, such as measuring melting ice in water (32F) or a gently boiling pot of water(212F)

All said, handy effective tools as long as you understand the limitations. I have and use one from this pricepoint.

The biggest thing I see with the more expensive ones is larger range of temperature. I understand there are similar limitations due to having a "room" or environment temperature reference node.

Phil

Bare metal surfaces are tricky for thermal imaging, as they emit less infrared and on the other hand reflect the surrounding IR radiation quite effectively. I have played with IR cameras at work, and even took a class a few years ago about it. These laser temp devices are sort of like ”one-pixel” IR cameras

I don’t remember the exact theory of the emissivity so well that I could explain it, but the rule of thumb was that bare metal is difficult. The instructor had a container made of copper pipe, part of it was polished, another part ”natural” and the rest was painted. He filled the container with boiling water and we aimed our cameras at it. Both unpainted parts showed something like 100F (barely warm, safe to grab), but the painted part showed the correct 212F (ow ow OW).

There are tables for the emissivity values of various materials, and the spec above indicates that the device can be adjusted accordingly. But still there will be reflections of sun or lights, or even your own body temperature can mess with the temperature reading of a reflective surface. It is all manageable as long as you know it, and as Phil said when you don’t need the absolute temperature.

At work we measured things like the cooling package (engine water, intercooler and hydraulic fluid cooler) of heavy machinery, or the temperature distribution of the exhaust system. With bare metal we got pretty confusing images but after we spray-painted the coolers, it worked well and we got nice videos and time-lapses on how the thermostats opened and how the cooling fan kicked in etc. Or how the intercooler and the exhaust system of a 9 litre JD diesel heated up when loaded 100% and cooled back down when the load was dropped. We intuitively used flat black paint because we had it on hand and it seemed most obvious but later learned that the colour does not matter. The paint is essentially plastic, and that is what matters, not the ”visible” colour.

On a model engine, maybe some water-soluble paint would make it easier to detect temperatures?

Some additional things to remember when inspecting small objects:
1. The measurement area gets bigger when the distance is increased, and the number you see on the display is some kind of an approximate average of that area.
2. This may be even more important, and not always very obvious. The laser dot is just a pointer and it has nothing to do with the measurement itself.
3. Also, the laser pointer and the measurement’s ”line of sight” are not on the same axis but off-set somewhat. Hence the laser dot is exactly in the middle of the measurement area only at one specific distance. On every other distance it is off the center. Or it may be even out of the measurement area on some distances.

The above points don’t matter a lot if you are measuring large objects, like radiators or walls, or if you are looking for hot spots in, say, a bunch of cables etc. But they do matter when checking out tiny stuff like our beloved little engines.

There are tons of stuff to read and videos too in the internet. Here is a short article about emissivity:

http://cambridgecarbonfootprint.org/emissivity/

Sorry to be so long-winded but this is an interesting topic

Would recommend this brand:

https://www.thermoworks.com/Infrareds

These devices fascinate me; as does the "emissivity" equation/quotient... but math/science was never my forte'.. so I remain stupid to such things..

RknRusty wrote:Got one. It looks tgtbt, but for $3 bucks I'll try anything.
Power Supply: 1.5V AAA*2PCS Batteries ( Not included)

I "can" surmise.. that a pair of quality AAA size alkaline batteries may very-well cost more than the device you purchased.. Rusty..

roddie wrote:These devices fascinate me; as does the "emissivity" equation/quotient... but math/science was never my forte'.. so I remain stupid to such things..

Theory is important but practical experience is importanter

For this emissivity thing, it is most important to know that it exists and to consider the accuracy of your readings accordingly.

And, "If in doubt, paint it black"

KariFS wrote:

roddie wrote:These devices fascinate me; as does the "emissivity" equation/quotient... but math/science was never my forte'.. so I remain stupid to such things..

Theory is important but practical experience is importanter

For this emissivity thing, it is most important to know that it exists and to consider the accuracy of your readings accordingly.

And, "If in doubt, paint it black"

I just couldn't resist, Kari..

https://www.youtube.com/watch?v=flSmiIne-4k