Measuring Temperature in Small Silver or Bronze Melts

Check Omega Engineering The provide a broad selection of thermocouples and measurement instruments. One consideration is the compatibility of the thermocouple alloys with the alloys that you are working with.

Thanks for the quick suggestion! I have perused Omega, and chatted with their online reps, but do not find anyting for a small scale 1000C melt.

Maybe a general search on "pyrometry" could help.

Seach for "laser thermometer". You can get one these days for less than fifty quid.

I vote with Crabtree.

Try a hand held laser unit.

They are cheap and close enough for what you are doing unless you are trying to automate the process.

Laser thermometers are actually infrared thermometers. :)

Read more : http://www.ehow.com/how-does_4962575_laser-thermometers-work.html
So, back to square one !

Good catch, so GA! I caught it too. Looks like somebody has oeuf sur son visage.

Yes but they provide a laser dot for focusing the sensor in the correct position to give the most accurate reading.

Hi gk1248,

Some here have mentioned "laser thermometers". I looked it up, and "laser thermometers" are simply infrared thermometers (IR pyrometers) using a laser pointer for, er well pointing.

Based on Ag, your melts are ~ 270 mL in volume, requiring an estimated 500mL vessel, presumably ceramic.

A primary question is "how long between when you sense the temperature until an action must take place?"

I'm thinking a fine-wire Type K thermocouple (TC) housed by an appropriately-sized ceramic tube, acting as the thermowell (TW). This would be placed in the melt from the open top of the crucible. Electronics can be had fairly inexpensively. I have some specific ideas about exactly how to do this, and I'll try to post them later.

Mike

Flir is also not cheap. Simple thermocouple or RTD will do. Search the internet.

Yes, Mike; that is the configuration I thought might work. I hope to discover if there are any members with experience with such a setup on as small a scale as mine. Alternately, I have considered drilling a small hole horozontally halfway through the base of the crucible, below the level of the insde bottom. (The crucible is .7" thick at the bottom.) The thermocouple & it's ceramically insulated wires would slip-fit into the hole; it's wires would run up the metal crucible handle to a small box cotaining either a millivolt meter or a small circuit board with an AD595 Thermocouple amplifier, a Microchip processor, appropriate firmware, and a digital readout. <Ah, dreams of glory!> I would of course not be reading the temp of the melt, but that of the inside of the crucible, which would act as it's own thermowell. I could perhaps find the temp correlation. Has anyone tried something like this? All suggestions are welcome - thnaks all for your comments!

Yes! I have used the AD595. With an output of 10mV/ºC, you could get by with a 10VDC supply for the IC, but I would go with 15VDC so you're not bumping the upper limit. You can output the voltage from the AD595 directly to a standalone voltmeter with an LED display. When I get home, I'll send a schematic and pictures.

By the way, when someone gives you some pertinent help, it's good form to give them a Good Answer. Click on <Rate>.

More later!

I had great success with a Fluke Multimeter using Type K thermocouples.

Try http://www.fluke-direct.com/product/fluke_51_ii_digital_thermometer

The type 51 was the one I used and found them economical. The infrared needs a clean surface and any dross or slag on the surface screws it up.

It's reasonably priced. I used Richardson Thermocouples with mine but some people would use RTD wire and cut off the ends when they got bad and re-twisted the wire for a new end. The thermocouples may be a bit too large for your application.

link

Here is a link to a jewelry tools company with thermocouples for a well in your crucible. page 544 has what you need. You Might enjoy the rest of the catalog too.

Thak you all! I will try the "drill a well into the cricible itself" route with one of the suggested type K thermocouples+readouts that have been suggested. Tnx again!

Now you got me thinking. Given that you are doing investment casting, you may have everything you need at hand to make a miniature thermocouple probe.

What you will need:

2 hole ceramic tube McMaster #87175k83 for 3/16 OD (smaller diameters are available) rated for 3000 F

Type K thermououple wire (from Omega)

An oxy-fuel torch to weld the thermocouple junction

Investment ceramic to coat the thermocouple junction and seal the ceramic tube and a kiln to fire the investment.

Mikerho: I mean to continue persiung the AD595 route. I welcome any schematics you may have on its use. Tnx!