How reliable is a thermometer?

To measure the temperature of the body you use a thermometer† Then you also know exactly whether someone has a fever and is therefore ill. A thermometer can measure body temperature quite accurately. It is important to get as deep as possible into the body. That is where the core temperature is.


Thermometers come in different types

There are 3 different types of thermometers. Each thermometer measures the Body temperature.

The forehead thermometer is the least reliable thermometer. The forehead thermometer measures the temperature outside the body through the forehead. To take a measurement, the forehead thermometer should be held about a ½ to 1 centimeter from the forehead. The temperature it displays varies between 0.2 and a maximum of 0.3 degrees from the actual body temperature. Because of the distance, there is a small airflow which makes for a lower temperature.

The ear thermometeris a more reliable body thermometer. But also with this one, it should come as close as possible to the body. The temperature can be measured by the eardrum. The eardrum has the same temperature as the body. To measure a correct temperature, the ear thermometerbe held well in the ear. The ear canal must be free so that the infrared signal has a clear view of the eardrum. In most cases, the thermometer should be held in the correct direction. Sometimes pulling on the earlobe can make it easier to pass through. Earwax causes the signal to be distorted. So make sure your ears are clean when measuring. That is also the reason that most ear thermometers use special ones lens filters. This keeps the ear thermometer clean. An ear thermometer can have a deviation of up to 0.1 - 0.2 degree.

The fever thermometer is the most reliable thermometer. It must be used properly though. A fever thermometer can be used in 3 different ways:

  • Axillary (under the armpit): this is the least reliable way. The temperature under the armpit deviates +/- 0,2 degrees from the actual body temperature;
  • Oral (in the mouth): although the thermometer is in the body, the temperature is still off. This is because there is air in the mouth which lowers the temperature. Orally, the temperature deviates +/- 0,1 degree;
  • Rectal (in the anus): this is the most reliable way to measure the temperature. The thermometer is in the body. This is the only way to measure temperature completely accurately.

As you can read, a thermometer can measure temperature quite accurately. That's why it is important to choose the right thermometer.

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