laser thermometer

[hiram]

http://www.meritline.com/non-contact-infrared-thermometer---p-37669.aspx?strcoup=&dealid=31419


read the reviews

[rexherring]

That's a great price. I paid $75 for the one I use at work.

[para45lda]

You may get faulty readings due to the reflectivity of the melt surface.

YMMV

Wes

[nwellons]

My laser thermometer does not correspond to my dial thermometer readings. The laser numbers bounce all over the place and so it is unusable for lead.

At least that is my experience.

[popper]

For $60 you can make an electronic one. Add $25 to make a PID.

[303Guy]

Could you direct me to the circuit for one, Popper?

[Radkins]

We sell one here at work for 27.00. It does not work well on molten lead, but will work good on anything that is not reflective as Para45lda said.

[shooter93]

I wonder how they would work for checking mold temp? Keeping the lead the same temp isn't bad but they might be nice to keep the mold the same temp. Wpildn't really matter what degree it read as long as it was consistent...any thoughts?

[Mike W1]

I wonder how they would work for checking mold temp? Keeping the lead the same temp isn't bad but they might be nice to keep the mold the same temp. Wpildn't really matter what degree it read as long as it was consistent...any thoughts?

I don't have any way to tell actually but when I used mine on molds that were at casting temperature I expected a higher reading than I got. FWIW my guess is they don't do the job for that either. I've also since found out that they need to be closer to the object than what one would think. The laser you see is apparently just for aiming them and not what is measuring the temperature.

[dragon813gt]

They are infrared thermometers. The laser is also usually not at the point of aim for the temp reading. I use them in the HVAC trade but for very few things. They have to be on the surface to get an accurate reading. Otherwise it senses over a larger area which will drive the temp up or down. And you can forget about reading the temp on any reflective surface. I have to put a piece of tape on a copper pipe if I want a decent reading. Without it I will get wild swings depending on angle and distance. Now the FLIR tool I have is great, but very pricey.


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[uscra112]

I'm going to boilerplate this, I have to repeat it so often.

I had to research non-contact temperature measurement in some depth, just before I retired. The systems I was working on required quick and accurate temperature data to control a high precision dimensional measurement process, which is widely used in auto plants while manufacturing blocks, heads and crankshafts.

Bottom line is: Non-contact temp measurement is both inaccurate and unreliable in the extreme. The industrial vendors could not guarantee us better than +/-5% of displayed reading, and then only if we submitted samples of our work to them so that that each instrument could be calibrated. This has to do with a property of material surfaces called emissivity. Emissivity varies widely with material, the color and roughness of the surface, and surface contaminants. Without surface-specific calibration, the expected error could be +/- 20% of displayed reading! That's what the suppliers said, not my opinion.

The laser, by the way, plays no part whatsoever in the sensing process. It is an aiming aid only. The sensing element is an infra-red photodiode. The manufacturing variance of the sensors is so great that they had to require us to re-submit material samples when a replacement sensor was purchased. And these were thousand-dollar sensors, in $5K systems, not "consumer-grade" gadgets you buy for $30 at Harbor Freight et.al.

Best you could hope for using an affordable non-contact device would be to calibrate it carefully against a known good thermometer, then mount the device so it always looks at the same spot on the pot, making sure that the area it sees is never any cleaner or dirtier over time, recalibrate every casting session, and hope for the best.

[azjohn]

303 the stiky for a PID controller is here.
http://castboolits.gunloads.com/showthread.php?t=115724