Cheap thermometer calibration technique?

You're kidding, right?

I am quite sure that the OP knows all about scale conversions, and even likely has a good grasp on direct "off the top of one's head conversions.

Pedantic idiocy, is what that remark is.

It has errors for IR instrument calibration.

Which is fine and dandy, HOWEVER, for IR, there ARE issues to consider.

For someone so pedantic, one would think you would care about such issues.

A black body CAVITY is the better source.

So... what... barely boiling... roiling boil... hearty, full boil?

All three have different temps.

For such a pedantic twit, you sure don't know when what matters and what doesn't.

Said the slanderous, retarded f****ng bastard of aed, aee, aem, aee, etc.

Nah you're just a drunk and that's forgivable.

Not drinking, and you're just a goddamned retard.

Both ice and water have IR emissivities of about 0.98... they are already as 'black' as things get. So crushed ice in water, freshly stirred, is a near-perfect 0 degree C IR target in any vessel. A thermos is ideal to keep it very close to 0 C.

John

One stove and one bucket of ice. Put thermometer in Boiling water. tha's 212F (100C) (at sea level).

Put thermometer ic ice bucket that has water up to just cover the ice. that;s 32F (0C). (We did this often in physics lab in high school and college!)

Angelo campanella

Angelo-

I've used this technique for standard thermometers.

However, the IR gun is a different animal. Its reading is dependent on the "emissivity" of the surface being measured. If DaveC looks at the specs of his, he will probably see an emissivity factor mentioned along with the accuracy data.

Fred

I would put money on the therocouple thermometer, for what it's worth.

Melting ice and condensing steam. For both you are going to need a small copper or aluminium block painted matte black for the IR temp gun to read and a hole drilled in the block thats a close fit for the thermocouple with a little dab of heat transfer grease. Implementation is your problem, although it can be advantageous to insulate the sides of the block with expanded polystyrene.

Water and ice have thermal IR emissivity of around 98%, about as black as things get. So mix crushed ice into cold water in a glass or cup, preferably a thermos, stir, and aim your IR thermometer straignt down into that. Or swish a thermocouple around in it. Even yukky tap water, well stirred with ice, will be within 15 mK of 0C.

The high end, boiling, is a little trickier.

John

ratman wrote in news: snipped-for-privacy@4ax.com:

How do you know the basic DMM is accurate? gotta use the RIGHT thermocouple,too.

Ice water bath in styrofoam cup and boiling water in pot. 32F and 212F. Can't get any simpler. (unless you are at some unusual altitude,like Denver)

But you could find corrections online,I'm sure,DAGS.

take a heavy gauge aluminum strip,paint exposed part flat black,and stick in cup/pot,for IR thermometer reading.

Simply apply a millivoltage equivalent to the thermocouple thermometer and see if it reads right (use a known-good DMM with a 200mV range). You'll need to know the ambient temperature accurately. When you short the input it should read the temperature at the jack. When you apply the mV (calculate from desired reading and ambient, given the type-- usually "K" = Chromel-Alumel) it should read that temperature.

The thermocouple itself will either work well enough or not at all, barring the most extreme circumstances.

Best regards, Spehro Pefhany

Each to their own, but i do not use thermocouples very often due to the "cold" junction compensation needed. It is just too easy to calibrate a thermistor instead.

The aluminum block is quite unnecessary, though an aquarium pump or lab stirrer is useful.

Deionized, distilled (chem lab high purity) water really helps in both cases.

Freezing and boiling water (compensated for altitude) is probably more accurate than the fancy IR thermometer, and a damn sight less expensive.