IR Thermometer calibration?

Hello all, with the current health crisis going on we’re seeing lots of people having their temperature checked as some sort of indicator of health status. This has also been implemented at my workplace, we get checked before entering the building. First they were using industrial IR thermometers (with visible laser pointers) and checking our foreheads. I said it was a bad idea to point a laser a few centimeters from someones eyes (the instructions say not to do this anyway). These types of thermometers also have a huge (and inaccurate, ± several degrees) range and they were abandoned. They then acquired a medical type designed for specifically checking body temps. So I questioned the management about how the units were calibrated, since they send us home if we’re over a predetermined limit. Upon checking the manual that came with the devices there is no mention of how to calibrate them. The instructions also said for indoor use only with ambient temp of 20-30c, we’re are being checked in the car-park where the ambient temp in the morning is now way below 20c. I was told I’m being “difficult” by asking all these questions of management.

With a bit of Googling I found lots of ways to check (but not calibrate) industrial types but this cannot be transferred to body temp types. As the range is very narrow and needs to be within a 1/10 of a degree.

So my main question is how do hospitals, Dr surgery’s & paramedics and other health professionals calibrate their gear?



Medical grade non contact IR thermometers are supplied pre-calibrated. There is no provision for user calibration.

This source suggests that if there is doubt an IR thermometer reading can be checked against a conventional Thermometer. Note that there the experts advise there are small variations in consistency between devices and method. IE typically small differences in repeatability and actual temperatures measured depending on which method is used.

Any other details concerning accuracy, proper use or limitations on usable lifetime should be included in the product documentation.

It is probably cheaper to dispose of a typical IR body temp thermometer than send it to a NATA certified standards lab for recalibration.


I bought an industrial IR Laser unit from Jaycar but it would only read around 33 to 33.5 degrees on the forehead so I returned it and received a no hassle refund.

However, there was no need to use the laser function which is there for targeting objects some distance away such as a wall whereby it projects two red dots so the operator can see what it is aimed at.

The laser function can be turned on and off as required.


The emissivity of a surface influences the accuracy of any IR thermometer reading. The condition of the material is also a factor. EG molten vs solid at room temperature.

Medical IR thermometers are designed specifically for their one task. In the following example measuring body temperature on the forehead.

The readings provide a quick indication of approximate body temperature. Note units with a TGA approval number may be priced with a premium.

We purchased an in ear digital and a pack of disposable caps, similar to our GP’s use.


Thats right, the sensor range for an industrial one is greater than that for a medical one. Accuracy will be based on the optimum reading/sensor temperature range…which will be vastly different. A medical thermometer will have sensors which measure accurately around that of body temperature…as they aren’t designed to measure say ovens or freezers…unlike the industrial ones.

It is a bit like using a industria clayl kiln to cook a pie for lunch…purposes and function is very different.


Nothing wrong with it, that is a typical skin temperature. I suspect the medical IR thermometers might use a longer wavelength and be more indicative of temperature under the skin, closer to core temperature. Also important, as Mark mentions above, is emissivity. Some units are adjustable, but cheap ones are not, meaning grossly inaccurate temperature readings on some materials with large offsets from the inbuilt assumed emissivity.


Thanks for the link to calibration of that particular model. :+1:

My workplace has a NATA certified testing lab and we calibrate all our temperature measuring gear, but it’s unable to test over a very narrow range with 0.1 deg accuracy.

This is why I was curious as to how health professionals and their workplaces calibrate theirs?

I also raised this question with management, as most of the readings were about 2-3 deg low and they were relying on this data to admit staff to the workplace. Again I was told that I’m being “difficult”

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I think @mark_m covered this in an earlier post. The non-contact thermometers used by doctors etc may have a specific design life where they remain in calibration (such as say 12 months) and after the service life, the thermometer is discarded as it is cheaper to buy a replacement which is calibrated than recalibrate a 12 month old one. The thermometer may not be designed to be recalibrated anyway.

All equipment which requires calibration has a period which after calibration is necessary. For any equipment, one has the choice to recalibrate it or buy a new one from the manufacturer which has been calibrated at the end if its production or tested to ensure it is within the specific testing design parameters on its manufacturer.

I know from days working at a university, some equipment such as bulb thermometers, if they aren’t within spec when tested at the end of manufacturing, they are discarded/destroyed. The same could apply for non-contact thermometers where those outside design spec at end of manufacturing are discarded, while those which are become sellable products. At the end of their usable life, they are discarded. They could also have a long life, say many years, like a bulb thermometer, if the equipment is looked after as use doesn’t deviate from when it was manufacturered.

Not all equipment needs calibration as a result.


The medical IR thermos may simply add “x” to the measured skin temp to give the predicted internal temp.


I’m not a medical professional, hence any comments that follow come with no assurance as to reliability.

The traditional method of using a mercury contact thermometer held under the tongue or inserted unceremoniously elsewhere has been superseded. In ear measurement, as well as electronic sensor based devices attached to the skin or inserted where… are my personal experience of treatment in theatre.

Assuming in your example a medical grade thermometer is being correctly used, are there any other concerns?

It’s worth noting that body temperatures vary between individuals slightly. Also if you just dismounted from your 25km bicycle ride or other when tested the reading will be elevated slightly.

In the instance of a high reading it’s worth asking for a second after a period of resting comfortably out of the sun. Perhaps also asking for a second reading with another device preferably an in ear digital body thermometer. These are not devices costing thousands of dollars. If your place of work has a NATA accredited lab, it would seem reasonable they understand the basic principles we are discussing. ISO accredited?


Thanks for the all the reply’s.

I think they meant difficult because I was asking all these questions that they didn’t have answers for.

My concerns where that all the readings seeded to be to low; some where 30-34deg. So any potential concerns would be missed.

The opposite happened to me, thus raising my suspicions even more. My cycle route to work involves a steady 5min climb (lots of sweating) about 3km from my destination followed by a down hill section. On cool mornings when I arrive at the entry my forehead is very cool (I assume from evaporation during the down hill part). They test me and the device just says LOW as it’s outside of its intended range, and I’m granted access to my workplace. No-one tests me later.

Yes, all the technicians and lab manager do. But the directive came from an overseas HR department for all sites to follow. I understand they are being proactive in trying to stop infections which is great, but the outcome seemed to be “token” at best.

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Perhaps more accurate results would come from using traditional contact-type thermometers. Just drop your pants and bend as you come through the front door. I have worked at places like that, it would be no change in procedure.


From another angle, I was recently refused dental surgery after IR thermometer indicted that I had a fever. I had just traveled to the day surgery in a non-air-conditioned taxi on a very warm day. I took my temperature with a traditional thermometer on arriving home and it showed 35.7 degrees. I realize that IR thermometers are necessary in a pandemic but I always carry my thermometer with me after this experience. I still haven’t had my surgery.