Just for grins and curiosity, I got out my IR temperature probe and ran an experiment to see how useful these devices might be for measuring the operating temperature of a Fiat engine. I heated up a stainless steel tea kettle on the stove until the water was vigorously boiling (by definition somewhere around 212 oF), turned off the burner and placed the kettle on an unlit burner, and quickly measured the temperature of the outside of the kettle. The IR probe is a Fluke 65 max+ model. I also stuck a mercury thermometer in the water, and it registered around 210 oF.
Result: The exterior of the kettle registered between 140 and 190 oF, and it bounced around a lot depending on angle, location, distance, etc.
Conclusion: At least for this probe and this experiment, the IR probe doesn't give a very reliable (accurate??) reading of the water temperature. I can't say how this might relate to measuring coolant temperature of a Fiat engine by measuring the block or cylinder head external temperatures, but there you have it.
I suppose the more accurate experiment might be to warm up my Fiat until the temp gauge stabilizes at 190 oF (where it mostly sits) and then use the IR probe to see what the engine measures. An experiment for another day. But, given that you can place your hand on most metal surfaces of the engine (except the exhaust manifold) without getting burned, my guess is that the exterior would read quite a bit less than the actual temperature of the coolant.
Your mileage may vary.
-Bryan
IR temperature measurements
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18Fiatsandcounting
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SteinOnkel
- Posts: 1000
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- Your car is a: 1978 124 Spider 1800
Re: IR temperature measurements
A friend of mine works as a fault analyst for a world leader in electric automobiles. One time I grabbed the IR meter to diagnose something on my car and all he said was "put that thing away, they are wildly inaccurate on metal".
The main issue is the different reflective properties of surfaces in an engine bay. You're really comparing apples to oranges with these things.
Cheers
Steiny
The main issue is the different reflective properties of surfaces in an engine bay. You're really comparing apples to oranges with these things.
Cheers
Steiny
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18Fiatsandcounting
- Posts: 3799
- Joined: Fri Mar 15, 2019 11:23 pm
- Your car is a: 1969 and 1971 124 spiders
- Location: San Francisco Bay Area
Re: IR temperature measurements
Steiny, I think you're right. My understanding of these IR temperature probes is that they measure the light emissivity of the surface being measured, at infrared wavelengths. However, my guess is that wool vs. shiny stainless steel vs. PEEK plastic might all be at the same temperature, but their emissivity in the IR region would be totally different. So, the IR probes give a very inaccurate reading for many surfaces.
As for my tea kettle experiment? I'm thinking that the shiny reflective surface of the tea kettle confused things, so it's not really a good experiment. I should strive to do better next time around.
Sorry for the TMI, but my background was as a physical chemist so this stuff kinda hits home for me...
-Bryan
As for my tea kettle experiment? I'm thinking that the shiny reflective surface of the tea kettle confused things, so it's not really a good experiment. I should strive to do better next time around.
Sorry for the TMI, but my background was as a physical chemist so this stuff kinda hits home for me...
-Bryan
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SteinOnkel
- Posts: 1000
- Joined: Tue Feb 19, 2019 9:31 pm
- Your car is a: 1978 124 Spider 1800
Re: IR temperature measurements
It's always good to deep dive into diagnostics tool.18Fiatsandcounting wrote:Steiny, I think you're right. My understanding of these IR temperature probes is that they measure the light emissivity of the surface being measured, at infrared wavelengths. However, my guess is that wool vs. shiny stainless steel vs. PEEK plastic might all be at the same temperature, but their emissivity in the IR region would be totally different. So, the IR probes give a very inaccurate reading for many surfaces.
As for my tea kettle experiment? I'm thinking that the shiny reflective surface of the tea kettle confused things, so it's not really a good experiment. I should strive to do better next time around.
Sorry for the TMI, but my background was as a physical chemist so this stuff kinda hits home for me...
-Bryan
It would be great to accurately measure the temperature of an exhaust header runner, especially when dealing with multiple throttle bodies. Alas, my ir reads different temps to the tune of +/-80C when pointed at a stainless steal header. Even though the vacuum gauges all the read the same, the AFR is steady at stochiometric and the plugs are all the same color.
They are okay for finding a plugged radiator for example, or determining if you want to touch a certain piece with your hand. Not for much else though I'm afraid.
My new multimeter has an actual, physical probe. I have yet to play around with that. Supposedly it can handle 1500C which not even a header reaches...
Cheers
Steiny