| masraum |
07-22-2020 03:23 PM |
I found this online and I suspect it touches on what I'm thinking.
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Yes and no, the body measure thermometers use a bolometer that is selected to have a good response at around 35-45C, and is calibrated to be accurate with a black body radiator ( the human skin in the ear and mouth is a pretty good black body approximation) to within 0.05C. the industrial sensors are only going to have 0.5C resolution and up to 2C of error at that point.
Using them to measure also requires knowing ( or taking a guess) at emissivity of the surface, you only get an accurate temperature with a surface that is the same or similar emissivity as the one it was calibrated to. Some you can set the emissivity, but your accuracy is poorer then, and the fixed units can have a very large error.
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Another quote from the 'Net.
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Yes, you can. I am an architect, not medical, but did a lot of work on actual vs perceived temperature.
Set the emissivity to 0.85, this is good for a range of skin types. For individuals, say, your family, calibrate the IR thermometer. Get them to breathe through the nose for one minute, then take a reading on the back of the throat. While doing the nose breathing, take the temperature under the tongue with a mercury or digital thermometer. Write down the readings, this will give you an indication of how they might differ in the future for this particular person. If the readings are the same, great! no calculations next time. If they are not, do it three times to get an idea of how the temperatures typically diverge. You are only looking for a fever indication; it doesn’t have to be accurate. Next time, just shoot them down the back of their throat and add their typical difference.
If you just want a general, fast indication that somebody has a fever, say, as people line up to enter a workplace, aim it at the forehead not the back of the throat. This will not be so accurate but will give a good indication. Skin colours will not have a significant effect on emissivity, actually, we are all just shades of coffee. Pull any anomalies off line, retest them on the forehead then confirm with a thermometer under the tongue or refer them to medical. Take into account the weather, how much exertion was involved in joining the line, and anything they were wearing on their faces, such as a balaclava. Expect everybody’s foreheads to be reading slightly lower than under the tongue, all you are looking for are the anomalies that warrant further scrutiny.
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Then there's this chart that says that skin is .95-.98
https://www.thermoworks.com/emissivity-table
This link seems to cover things pretty well too.
https://www.thermoworks.com/covid-19-screening
Quote:
ThermoWorks other infrared thermometer products are intended for food service, food processing, industrial, scientific and general home use. They are not FDA Cleared for clinical use. However, in the current pandemic environment, there is a worldwide shortage of infrared sensors and medical infrared thermometers. With proper technique, general-purpose infrared thermometers might be used as a substitute scanning tool for detecting elevated body temperatures. We offer the following information and cautions:
Forehead temperature is several degrees lower than core body temperature of 98.6 F (37 C). Clinical forehead thermometers make a mathematical adjustment to display an equivalent oral temperature. When using general-purpose infrared thermometers to read forehead temperatures, the readings will likely be lower than 98.6 F, even if a fever is present. Normal forehead skin temperature can vary several degrees depending on your environment (indoors or out), exercise, perspiration, direct heat or air conditioning, etc. It would be normal to read an actual forehead skin surface temperature between 91F and 94F if using a general-purpose infrared thermometer.
Some infrared thermometers have an “adjustable emissivity feature”. Some are factory set for emissivity of 0.95, or in the case of our IRFS, 0.97. Human skin temperature is in this range. If using a fixed emissivity infrared thermometer, one could measure temperature in the center of the forehead, and then add 5 degrees Fahrenheit to estimate the oral equivalent.
Or, to simplify things for the operator, one could measure each subject and look for a “normal” temperature of 91F to 94F without making any adjustments or offsets. A higher reading might indicate a fever. Still, such a scan could not be regarded as a reliable absolute measurement of core body temperature, only a scanning or screening indication.
Users should be aware of the “spot size” of the infrared thermometer’s measurement area. They should also consider the distance-to-target recommendations of the instrument. The angle of the sensor to the subject is also important.
If the general-purpose IR thermometer has a laser-pointing feature, it is best to turn the laser off if possible (or cover it with tape) and always use great care to avoid pointing it at someone’s eyes. The laser is not part of the measurement technology and is only used to assist in aiming.
Some industrial IR thermometers allow the adjustment of the emissivity setting. In medical literature human skin is noted to have an emissivity between 0.95 and 0.99 regardless of color. By setting an adjustable emissivity to 0.78, the instrument will give a forehead temperature reading that approximates the normal oral temperature. This approximates an “offset” to the reading that will render a measurement near 98.6 F on the forehead of a healthy individual.
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