Cheap thermometer calibration technique?



Doesn't 63/37 solder melt at 485° F at sea level?
That would calibrate the thermocouple.
The IR is a bit trickier as the surfaces you examine have differing emissivities.
You likely have a calibrated instrument, but forget to shift for emissivity differences.
For the IR to cal correctly, you need a "black body calibration source, which is typically an Aluminum ingot painted with IR paint.
You can learn a lot here:
http://www.mikroninfrared.com/App_Notes/Principles_of_IR.pdf
These guys are the tops.
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DaveC wrote:

Use a melting ice cube for zero C, and boiling distilled water (in a clean container) for 100 C.
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Actually, the international standard is a bunch ice covered in water a stirred well. The standard clearly says that this must be done in your own coffee cup and the stirring must be done with a plastic coffee stirrer. You have to stir it up while standing in the company kitchen and then measure as soon as you are done stirring. You can't stop to answer the "What the heck are you doing?" question from the cute accountant.
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You really need a set of temperature standards. Temperature standard equipment is expensive.
On a laser temperature reader, there is the EMS "emisivity) factor. You must set the EMS of the reader to be proper for the type of object you are measuring. If the EMS is not adjustable on your reader, then the reference object must be of the correct colour and type of material to be referenced.
If your reader is expensive to replace, I would suggest you send it to a calibration lab that can check these types of units.
A crude way of checking the temperature accuracy is to use ice water with crushed ice, and measure the water. This should read within about 0.5 C under ideal conditions. You can boil some water, but the borametric pressure facture must be considered. This should be able to reference to within about 0.5 C. The water must be purified water. Tap water will have minerals in it, and its boiling point will be effected.
Jerry G ===

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This popped up -- a home-made RTD:
< http://www.sciam.com/article.cfm?articleID 06869F-5263-1C6D- 84A9809EC588EF21&sc=I100322>
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DaveC
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In the first place, the OP was dealing in F, not C. In the second place, this is neither a crude nor inaccurate method of calibration. In the third place, we have data that shows that for crushed ice, water, inside of a decent thermal chamber (like a thermos bottle) it will be within millidegrees of 32 °F.
You can boil some water, but the

That's "barometric" last I looked. The correction factor has already been posted ... 29.92" Hg. is the reference pressure and the correction is approximately 1 °F for each 1" Hg. drop in pressure ... which is one HELL of a drop. Just for reference, 1" Hg. is approximately 1000' of altitude from sea level.
This should be able to

The spelling is "affected" and the requirement for purified water is horsefeathers.
Jim

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"RST Engineering (jw)" wrote:

You're wasting your time trying to correct Jerry. Read some of his posts on news:sci.electronics.repair and you'll see that he just doesn't care. I looked at his business website once, and it was just as bad.
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On Thu, 10 May 2007 08:22:09 -0700, "RST Engineering \(jw\)"
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.
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On Thu, 10 May 2007 08:22:09 -0700, "RST Engineering \(jw\)"

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.
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On Thu, 10 May 2007 08:22:09 -0700, "RST Engineering \(jw\)"

So... what... barely boiling... roiling boil... hearty, full boil?
All three have different temps.
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On Thu, 10 May 2007 08:22:09 -0700, "RST Engineering \(jw\)"

For such a pedantic twit, you sure don't know when what matters and what doesn't.
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There are various temp sensor IC's (LM35 et.al) that can be had in +/-0.5degC accuracy grades. If you can get some samples, then they are FREE.
Of course then you have all the other surface issues that everyone else is talking about.
Dave.
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wrote:

There's that word again...
SURFACE!
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DaveC wrote:

Having suggested in an earlier post that water and ice might not be "friendly" sources in IR pyrometer calibration, it is worth reading the following thermometer calibration guide:
http://www.oznet.ksu.edu/library/fntr2/mf2440.pdf
While the guide provides detailed methods for using water in the calibration of bi-metal, thermocouple, thermistor, and other thermometers, it says the following about IR thermometer calibration:
IR thermometers are calibrated using a “Blackbody,” which emits a given amount of energy at a given temperature. A blackbody calibration instrument is expensive. However most manufacturers of NIST IR thermometers provide a calibration service for a nominal fee for yearly calibration and certification.
On the other hand, AEMC (an instrument manufacturer) offers the following water/ice calibration technique: http://www.aemc.com/techinfo/appnotes/EnvironmentalTesters/CA870_872_876_CalProcedure.pdf
Please note AEMC's concept of acceptable errors using these standards! That should explain why serious calibration requires a cavity-type blackbody source.
One can usually calibrate an instrument using a variety of standards, but it is prudent to understand the errors each introduces.
It's yet another instance of the "good, cheap or fast - choose any two" constraint.
Chuck
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The "experts" in the group would rather simply have you and everyone else believe that I am off my rocker.
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On Thu, 10 May 2007 17:17:19 -0700, The Great Attractor wrote:

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

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

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