Contactless thermometers – efficient measurement for medical environments
Skin temperature is a mixture of core body temperature and ambient temperature. That’s why you need to measure at a location that will give a value related to the core body temperature. There are several standard ways of taking a person’s temperature. Rectal is most accurate and reliable to determine the core temperature. Oral and axillary are also good methods, which are more convenient. However, these traditional approaches can easily take a minute. In medical applications where time is of the essence, contactless thermometers are significantly more practical.
How does contactless thermometers work?
Contactless thermometers are equipped with optical sensors that detect radiation emitted by an object from a distance. Light from the object is picked up by a ‘thermopile’ – an electronic device that converts thermal energy into electrical energy. This electricity is measured within seconds. Temperature is generally taken in the ear or on the forehead. As nothing is inserted, this is quick and comfortable and results are available almost instantly.
Accuracy contactless thermometers
Accurate measurements can be provided in less than 1 second by scanning the forehead. During a manual scan, the instrument records hundreds or even thousands of data points and picks the hottest spot to calculate the core body temperature. Accurate measurements do require the user to choose the best measurement position on the forehead. Readings are also affected by ambient temperatures.
Contactless thermometers are also often used to take temperature in the ear. Because the sensor is close to the in-ear canal, the reading isn’t strongly affected by ambient temperature. As in-ear temperature is directly related to core body temperature, which can be derived from in-ear temperature. This makes the in-ear thermometer the most reliable IR thermometer. However, users no need to measure specific areas in the auditory channel, and this method is less convenient than forehead thermometer measurements. The sensor also has to be clean to get the correct temperature value.
Readings can be obtained in a matter of seconds without touching, making contactless thermometers more convenient than conventional devices. There is no need to worry about sterilizing the thermometer before each use, or worry about contamination or transmission of infections.
Thermopile arrays are frequently used for contactless thermometers. These turn infrared radiation to heat, which is turned into electricity, and then measured. This is done without any shutter or external cooling, which means the devices require little power and maintenance and are cost-effective, unlike temperature measurement devices using a ‘micro bolometer as a detector in a thermal camera. These have a high pixel resolution and good signal to noise ratio but require frequent recalibration.
For clinical application, the measurement range should be from 35.5°C to 42.0°C with an accuracy of ±0.2°C or better. Peak infrared skin emission wavelength is approx. 9.4 µm -9.2 µm. Thermopiles optimized for highest detectivity in this range are the best choice for this application.
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Do you want to learn more about our contactless thermometers and other IR solutions? Get in touch with one of our specialists.