Taking infrared temps

[aussie460mag]

Hi,

Has anyone had experience using a temp gun to measure molten lead? It seems to reflect off the surface and reads about 250 deg, maybe a dark steel button to aim at would work?

[XWrench3]

no, i have not tried that. i do not know why, i have a ray-tech thermometer. i am busy today, and the weekend is here, it will probably be monday at the earliest before i can try anything. have you tried putting a layer of saw dust on top of the silver puddle to see if that works? give it enough time to get "used up" (finished baking might be better wording) before you take a reading.

[altheating]

I use a infrared thermometer in my heating business and have tried it on lead. No good! Get your self a Brownells lead casting thermometer. $20 or so, well worth it. The infrared thermo will work for mould temps, just make sure you shoot for the same spot every time you test.

[rays308]

heat sensing thermometer will give outside reading of hot pot which is hotter than the lead.
Hot gases from flame type setup can interfere with readings also.

As suggested above you really should use a thermometer that submurses into the metal. Stir a little while taking the reading.

If you use thermal sensing on your molds, test with it off the hotplate, away from the pot or other heat sources. They tend to give readings of whatever is the hottest.

[303Guy]

Infrared doesn't work with a reflective surface. It will indeed pick up reflected heat from the surrounds. A black metallic button floating on the lead might work. Any dross will alter the reading by either being hotter than the metal underneath or cooler. A big problem is that skin temperature can cary quite a bit - just a gentle breeze can cause a momentary drop and that's the part being measured.

[uscra112]

I've posted on this before. Even under ideal conditions, NO non-contact temperature device is accurate unless the device is specifically calibrated to the emissivity of the object being measured. I learned a lot about these devices during an engineering study I did while I was supporting precision measurement systems for GM and Ford. There were some non-contact systems that would do fairly well, but the cost of calibrating them was in the tens of thousands of $$, and it had to be re-done whenever you replaced a sensor. Out of the question for our projects. Inexpensive hand-held gadgets may read out to +/- five degrees, but they could easily be over a hundred degrees off the real temperature.

[Jim Flinchbaugh]

I've tried my Rateck and came to the conclusion that it is just reflected off, So I bought a real ion from NOE :D

[rintinglen]

toss an Iron screw--nice and dark--on top of the melt and let it set for a few minutes then read that temp. Trying to read the lead temp directly will read way low, the reflectivity of that shiny metal interferes with the measurement.

[uscra112]

Reflectivity has nothing to do with it. That little red laser is just an aiming assist. It has nothing to do with the actual measurement. It's the emissivity of the surface you are looking at that matters. Yes, shiny surfaces have lower emissivity. Reading a piece of blackened iron floating on the melt will give you a different reading, but unless you calibrate your instrument against a known-accurate contact thermometer, you still may be way off.

[KYCaster]

...Reading a piece of blackened iron floating on the melt will give you a different reading, but unless you calibrate your instrument against a known-accurate contact thermometer, you still may be way off.



That's true.......not only for temperature measurement, but for size, weight, hardness...whatever.

But, very few of us have the means or the knowledge to calibrate the measuring instruments we use for our hobbies. The best we can do is standardize our methods so our measurements are repeatable.

If I can get my infrared thermometer to show the same temp time after time and detect the change in temp as the pot cycles on and off, then that's all I really need. By trial and error I can find the temp that works for me and with consistent and repeatable methods I can reproduce that temp on demand. It doesn't matter if my thermometer reads 50 deg off...as long as it's consistent, I can repeat the condition that works.

Too many people get hung up on absolute values when, in reality, it's impossible to duplicate someone else's results without a detailed description of their measurement methods, calibration procedures and range of precision...AND the ability to duplicate those same conditions.

After all, "It aint rocket science!"

Wellllll.........maybe it is....a little bit.......kinda, sorta. :confused:

Jerry