IR thermometer saves the day! (story)

[Mr RB]

Bryan, that's the problem Scaedwian was talking about. It's to do with the reflectivity/emissivity of the thing you are measuring. I bet your coupling was shiny metal? Then the temp would read a lot lower than it was. If you has painted it with some UHT exahust paint you would have read the correct temp.

If you point the IR therm at some shiny metal it's like a mirror and it reads the room temperature that was reflected. One of the first things I did with mine was point it at the chromed parts of a hot Harley engine and it was reading room temp, because the room temp reflects in the chrome! Also if you point it in the oven to read the temperature of something in the oven it reads the temperature of the glass in the door, it can't read the temp THROUGH the glass door which is a pain.

You can fix the problem reading temps of shiny metal by painting some white-out or use a sticker or any colour matte paint. But I don't know any way to fix the problem of reading through the glass oven door.

 

[bryan1]

Ah and who said 'ya can't teach an ol' dog nu tricks' Thanks for that well explained post Mr.RB, I definitely try that out at work and I'll take along my good dmm and thermocouple and do a few tests. In the manual it's says nothing about reflectivity or anything similar so that is very handy knowledge to have

 

[Sceadwian]

bryan1, one trick I've learned looking up emissivity charts that would apply in your case. Soot is pretty close to matching the default 95% emissivity general IR meters are calibrated for. I think a quick blast of nearly pure Acetylene should put enough soot on the shaft you're reading to get a decent direct reading, just not so thick as the soot insulates the heat. You're lucky the coupling was moderately oxidized, cause if it was shiny metal and you heated it up to the 'proper' reading it would nearly be glowing white hot =O The heat forms a basic oxide though on pretty much everything so with ambient air I think worst case is gonna be close to 70% or so so you're only reading 25% high. From the numbers you gave you're only off 10%, but my off the cuff math is pretty bad =P

In my case with the chip heat sinks aluminum is nearly a worse case scenario, the oxide layer isn't very thick and the heat isn't even close to what you were dealing with. Although it suddenly dawned on me I could use a candle to put a soot mark on a fin =P

For a quick general refrences
https://www.electro-tech-online.com/custompdfs/2010/01/TableofEmissivity.pdf

 

[mbarazeen]

the meter only measures from whats radiated from the surface, a black body radiates perfectly. but shiny surfaces are poor in radiating power from it. that is the reason the meter cant measure it correctly some times.
i dont think its required to be mentioned on the manual about the surface property.

 

[Sceadwian]

It most certainly should be required in the manul The basic concept of emissivity is critical in understanding how to use an IR non contact thermometer... For a polished metal surface vs an otherwise highly emissive one we're talking about a reading variation of over 90% of what's on the screen! At the VERY least on the cheapest IR thermometer you buy you should find the fixed emissivity listed in the manual (almost always 95%) simple research on what that means should explain the rest. And it's not the shininess that is important, I have mirrors in my house that read perfectly normal, it's the base material itself and it's condition which are important.

 

[scarygood536]

good catch! #1 cause of electrical fires is poor termination! Having said that make sure you twist your wires together before you put the wirenut on. I know my house is scary now it was built in the 70's and we have been experiancing outlets that are getting warm. I dont know why but the electrician that wired my house used all stab in connectors. The stab ins weren't ment for 12 gauge wire. Dumb stab in connectors

 

[Sceadwian]

I lived in a lot of duplex apartments in my area that were over 100 years old, many without updated electrical... Scarrrrrry stuff 100 year old Aluminum mains wiring =O

Building owners tried to ignore problems from tenants as much as possible because a basic light dimming problem could discover massively out of code electrical for the entire building and cost 10s of thousands of dollars to bring up to code.