Calibration of an infrared thermometer - is it needed?

Question

Calibration of an infrared thermometer - is it needed?

starflex (Materials)

(OP)

26 Apr 17 01:03

Hi everybdy,

Quick one.

I just purchased an infrared thermometer (Fluke) to check the pre-heat temperatures before welding operations. The thermometer is provided without calibration certificate, but with a declaration (in essence, a quality document).

My question would be:

1. Do I need to do a formal calibration of a new instrument;
2. Is there any sense in calibrating an instrument, when the reading is strictly dependant on the emissivity of the surface?
3. How often would you calibrate it, in case?

Thank you in advance!

P.

IRstuff (Aerospace) · Answer 1 · 2017-04-26 01:36:31

It depends on what you plan on doing with the data. If this is part of a certified process that you will issue certifications for, then I would think that you'd want the instrument calibrated.

You could probably get Fluke to do the calibration. I would guess that it's a yearly thing.

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MikeHalloran (Mechanical) · Answer 2 · 2017-04-26 01:37:49

Some IR thermometers have a dial that provides a built in fudge factor for emissivity.
If yours doesn't, you might do a semi-formal calibration on representative workpieces.
Actually, I'd do that at least once, even if the meter had such a dial.

Mike Halloran
Pembroke Pines, FL, USA

starflex (Materials) · Answer 3 · 2017-04-26 01:39:43

Thanks IRstuff,

Problem I am facing at the moment is that I am in Malaysia, and the time required to do the calibration is 2 weeks (!). My instrument got lost (....) during the travel, so I had to source one locally (it's a Fluke).

I agree with your view.

Thanks,

P.

IRstuff (Aerospace) · Answer 4 · 2017-04-26 01:56:58

Depending on your accuracy requirements, you might be able to calibrate the instrument yourself. Fluke, and presumably others, have guides for performing the calibration: http://us.flukecal.com/literature/articles-and-edu...

http://www.thermoworks.com/learning/infrared_tips_...
http://www.thermoworks.com/learning/infrared_therm...
https://www.omega.com/literature/transactions/volu...
http://support.fluke.com/hart-sales/Download/Asset...
http://www.scigiene.com/TW814-132
http://www.scigiene.com/pdfs/Infrared-Thermometer-...
https://thermometer.co.uk/content/107-how-to-calib...
https://www.tempcon.co.uk/2012/04/17/calibrating-a...

A high-end PRT and a Krylon 1602 ultra-flat black painted copper block can go a long ways.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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MikeHalloran (Mechanical) · Answer 5 · 2017-04-26 02:08:54

I'm used to monitoring the temperature of stainless steel pipework, which may have a mill finish, or may be mirror-polished. A small square of black electrical tape removes enough uncertainty for my purposes, and makes sure that each series of measurements is associated with the same particular locations.
The tape would probably suffer at welding preheat temperatures.

Decades ago, before IR thermometers became available, SOP was a stroke of Tempil(r) crayon, which melted at a specified temperature. Can you still get them?

Mike Halloran
Pembroke Pines, FL, USA

Compositepro (Chemical) · Answer 6 · 2017-04-26 16:39:53

An old traditional way to get a high emissivity surface was to use a candle flame to soot the surface.

MintJulep (Mechanical) · Answer 7 · 2017-04-26 17:56:36

If you have a calibration control system then "New from manufacturer" for date of last calibration is unlikely to upset any auditor.

Regardless.

IR thermometer to check weld preheat is useless.

Emissivity changes as temperature changes.

Recently we had a fabricator try to do use an IR gun. We made them try to establish the E setting using a contact thermocouple on the same joint.

Didn't take long for them to give up and just use the contact thermocouple to measure the preheat.

But the temp-a-sticks work well too. Never have a dead battery, never break, don't need calibration, don't get borrowed.... http://www.markal.com/temperature-indicators/therm...

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Calibration of an infrared thermometer - is it needed?