10 replies to this topic

[rexy]

Hi brains trust,

 

I’ve been playing around with an IR gun measuring some temps and would like to know if anyone has some hard data on what the likely difference is between measured surface temp of a radiator hose and the true temperature of the water/coolant within.

 

I appear to get 80 degrees C surface temp of the upper hose while the gauge reads about 95 degrees. The gauge is a traditional style aftermarket VDO electric.

[claysummers]

Rexy I believe the best value of that tool is to check relative temperatures between top and bottom hoses. I wouldn’t be too confident making outright comparison to other data. Too many variables.


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[Rockoz]

Rubber is an insulator by nature, so the temperature between the inner and outer surfaces will likely be different.

Same theory as using insulation in the roof of your house.

When I was playing with V16 Cat engines, the technicians used infrared temp measurements a lot.

From memory, they only ever pointed it at metal surfaces. 

That gave better readings. And they generally measured other surfaces around the point of interest to get relative values.

 

Cheers

 

Rob

[Heath]

Even with metal surfaces, shiny surfaces are a bit of a drama, also.

[grumpy xu1]

Rubber is an insulator by nature, so the temperature between the inner and outer surfaces will likely be different.
Same theory as using insulation in the roof of your house.
When I was playing with V16 Cat engines, the technicians used infrared temp measurements a lot.
From memory, they only ever pointed it at metal surfaces. 
That gave better readings. And they generally measured other surfaces around the point of interest to get relative values.
 
Cheers
 
Rob

Hi Rob, main thing we ever measured was bearing temperatures on pumps & rollers ect, whilst i was doing that, basically part of the PM schedule, if they where getting bad, obviously we got results. People's lack of concern whilst doing the job was the main problem we had. Some of them really didn't take things seriously.

[RallyRed]

Good question.

I seem to recall from a few years back, that some of those IR guns required that the "emmissivity" be set for different types of surfaces. 

i.e. shiney steel vs. black rubber etc etc etc.

That must have some impact on readings?

[Rockoz]

Hi Rob, main thing we ever measured was bearing temperatures on pumps & rollers ect, whilst i was doing that, basically part of the PM schedule, if they where getting bad, obviously we got results. People's lack of concern whilst doing the job was the main problem we had. Some of them really didn't take things seriously.

 

 

I learned early in the piece that a touch test was pretty good for most bits of gear.

You got to know the rough temp that most things ran normally at.

But that was purely electrical stuff.

Always did a touch test on transformers and all the accessible electrical motors.

Secondly was the sound test. Most things have a particular sound when they are running normally.

Small vibrations from bearings about to go will change the sound.

Even though infrared temp readers were available, they werent allowed to be used without other regimes in place when working in underground coal. Or around the alternators hooked onto the V16 Cats running on coal seam gas.

 

Cheers

 

Rob

[rexy]

Thanks for the replies.

I am aware of the limitations of use and the many various other applications of IR measurement but was after any real world data relevant to my original question.

 

So has anybody done comparative measurements?

[skap]

If you had posted this a few days ago you would have been in luck.

 

I have a temp sensor plumbed in to the top radiator hose of the Valiant.  I also have an infrared heat gun thingy.

 

If she doesn't sell at Lloyds ending on Jan 29, then I will do a direct test for ya

[axistr]

I purchased my IR gun twenty years ago when they first come out. I had to get mine from the U.S as they initially were not available here. I should have waited 18 months because I paid over $800.00 Now you can pick them up from your local Bunnings for $65.00 probably not as good quality but as previously said they are a comparison tool. I use mine for reading exhaust temps at the manifold to give me information on exhaust burn temps between cylinders. It can quickly tell you if a cylinder is out, running rich or lean. Although I use it on petrol engines the main reason for purchase was for large diesel engine diagnostics. But found discovered so many other useful and handy checks around vehicles the house.     

[rexy]

Interestingly when I select intermediate surface reflectivity on mine it gives a temperature very close to the gauge reading.

If I get motivated I might try to do some proper comparative measurements and see how close it really is.