IR thermometer calibration source

[mookins]

Hi,

I currently have a black body calibration source which I use for work.
It works great, I can calibrate all the IR thermometers just fine, however it isn't a simple quick "check". The IR thermometers are the ratio type in that they measure two wavelengths and using the ratio it can work out the temperature.

I was wondering if it would be possible to use something like two lasers at the detector wavelengths to simulate this for day to day checking purposes? This would be to pick up on damage that may have occurred to the optical fibre leads or lenses from the harsh industrial environment they operate in. Accuracy would not be critical, just stability as they would be checked against a laboratory IR thermometer which would not be exposed to this environment.

LEDs or any other light source would be fine, I was thinking even incandescent light bulb, provided I could get a filament large enough.

On the topic of incandescent light, since the filament is so small and hard to "aim" at, what mechanisms are possible for getting a relatively even spot of light to aim at?

 

[Andy Resnick]

What is the temperature range, and what accuracy do you need for onsite calibrations?

 

[mookins]

725°C to 1200°C is the range that we calibrate the devices against the black body.
With regard to accuracy, the in-situ check will be cross checked, that is, we have a "laboratory" unit which we will take to the pyrometers in-situ, measure the "check" source then compare that to the in-situ unit. If there are any abnormal deviations it may indicate a problem with the lens, fibre optic lead or something else.
In essence, I was hoping not for a quantitative report but merely a means to see if the unit is operating correctly (with good confidence), within its operating limits.

By doing it daily it will give us early warning and we may choose not to release products that may not conform to specifications. We will still do our usual 3 month calibration against the black body source for every unit.

As for the pyrometer units, they have an average of about 10°C uncertainty in the 700-1200°C range. The main pyrometers we use, Raytek (Fluke) do not have any information about their detector wavelengths. We do however have a Lumasense (Mikron) and that operates at 0.9 µm and 1.05 µm.
I do know the Raytek calls the two channels in it's software, 1W and 1N for wide and narrow respectively. Perhaps they use a different technique that the standard ratio method I am unsure; maybe ratio of areas of spectrum, one with a wideband sensor and one with a narrow band sensor?