In short: the principle of operation. In a mercury thermometer, readings run up due to expansion W. Chen. Thermometry and interpretation of body temperature / Biomedical Engineering Letters substances inside a glass flask, and its digital counterpart receives Thermometers: Understand the options / Mayo Clinic information from a thermistor — a metal tip with a special coating. Therefore, the first one shows the maximum temperature during the measurement, and the second one shows the average. But this does not mean that the electronic thermometer is less accurate. Let's say you hold it under your arm for 10 minutes. For the first 6 minutes, your temperature was 37.3 °C, and then dropped to 37.1 °C. The device is likely to show 37.2 °C. An error of 0.1 degrees is generally acceptable.
In addition, a comparative meta-examination of the accuracy of different medical devices did not reveal V. Pecoraro, D. Petri, G. Costantino, et al. The diagnostic accuracy of digital, infrared and mercury-in-glass thermometers in measuring body temperature: A systematic review and network meta-analysis / Internal and Emergency Medicine there is no significant difference in the readings of mercury and electronic thermometers. However, it also called the ear infrared thermometer the most effective of all devices. This is because the temperature of the eardrum is considered N. B. Ciuraru, R. Braunstein, et al. The influence of mucositis on oral thermometry: When fever may not reflect infection / Clinical Infectious Diseases most accurately corresponds to the temperature of the whole body.
Sometimes people are faced with the fact that the readings of the electronic thermometer do not rise even to 36.6 °C, not to mention higher values. There may be several reasons for this.
When it comes to technology, you always need to remember about such a risk — a non-working battery can stand even in a brand new device. There are almost no factory malfunctions in mercury thermometers: if there are no cracks on the bulb, then the liquid inside will "work" almost forever. There are slightly more variables in the digital thermometer device, which means that a manufacturing defect cannot be excluded. For example, the readings may be affected by weak contacts of the thermistor with the display: the metal tip will correctly read the temperature, but the data will not reach the screen.
Unlikely, but not impossible. The fact is that in different countries, the usual place for temperature measurement differs. For example, in the USA and Europe, the oral method is more often used. Therefore, when buying foreign-made devices, you need to keep this in mind. Technically, the basic thermometer is able to measure the temperature on any part of the body, but the method of application will be different, and the instructions may be written by default for oral use. Let's say you read that you need to hold a thermometer for a minute. This is enough when you put it under your tongue, but 60 seconds is definitely not enough to measure under your arm.
This is possible with non-contact infrared thermometers. These are the ones that look like a gun with a red beam. They can be used for household purposes, for example, for use during cooking. Such devices do not undergo a special calibration procedure, so they can be mistaken by several degrees. Most likely, in pharmacies you will not stumble upon a household appliance, but if you buy in a supermarket or order online, then it is real to miss. In addition, medical devices must have a registration certificate — you can check a specific manufacturer in the Roszdravnadzor registry.
The main rule before using any gadget is to read the instructions. In the case of a thermometer, this is also important. You cannot work with the digital version in the same way as with mercury, focusing only on an old habit. There are some tips that are worth considering.
If you still think that the thermometer is lying, then try switching to an oral measurement method. First of all, it is considered Fever temperatures: Accuracy and comparison / PeaceHealth is more accurate, and secondly, it takes less time. You need to:
At the same time, remember that the temperature in the oral cavity is higher Fever temperatures: Accuracy and comparison / PeaceHealth than under the arm, by about 0.3–0.6 °C. Therefore, when you see "37" on the display, you should not be afraid. Most likely, you have 36.6 °C.