The electronic clinical thermometer is composed of a temperature sensor, a liquid crystal display, a button battery, an application specific integrated circuit and other electronic components. It can measure human body temperature quickly and accurately. Compared with traditional mercury glass thermometers, it has the advantages of convenient reading, short measurement time, high measurement accuracy, memory and buzzer prompts, especially electronic thermometers do not contain mercury, which is harmful to the human body. The surrounding environment is harmless, especially suitable for use in homes, hospitals and other occasions.
Electronic clinical thermometers use certain physical parameters of certain substances, such as resistance, voltage, current, etc., to display the body temperature in digital form by determining the relationship between the physical parameters and the ambient temperature. The disadvantage is that the accuracy of the indication is affected by factors such as electronic components and battery power supply, and is not as good as glass thermometers. Utilizes the characteristics of semiconductor resistance that changes with temperature.
Electronic thermometers use temperature sensors to output electrical signals, directly output digital signals or convert current signals (analog signals) into digital signals that can be recognized by internal integrated circuits, and then pass them through displays (such as liquid crystal, digital tube, LED matrix, etc.) Display the temperature in digital form, can record and read the highest value of the measured temperature.
The core component of the electronic clinical thermometer is the NTC temperature sensor that senses temperature. The resolution of the sensor can reach ±0.01℃, the accuracy can reach ±0.02℃, the response speed is <2.8 seconds, and the annual resistance drift rate is ≤0.1% (equivalent to less than 0.025℃).
Temperature Sensor
1. The phenomenon that the resistivity of the thermal resistance sensor material changes with temperature is called the thermal resistance effect. When the temperature changes, the resistance value of a conductor or semiconductor changes with the temperature. For metals, when the temperature rises, the resistance value of the metal will increase. In this way, within a certain temperature range, we can determine the measured temperature by measuring the resistance of sensitive materials. The sensor made according to the thermal resistance effect is called the thermal resistance sensor. Thermal resistance sensors can be divided into two categories: metal thermal resistance and semiconductor thermal resistance according to the resistance-temperature characteristics. Generally, metal thermal resistance is called thermal resistance, which is usually made of metal materials, such as platinum, copper, nickel, etc.; while semiconductor thermal resistance is called thermistor, it can be a ceramic device made of semiconductor materials, such as manganese and nickel. The oxides of metals, diamonds, etc. and other compounds are sintered in different proportions. The temperature coefficient of thermal resistance is generally positive.
2. The resistance value of the thermistor sensor metal increases with the increase of temperature, but the opposite is true for semiconductors. Its resistance value decreases sharply with the increase of temperature and exhibits nonlinearity. At the same time as the temperature changes, the resistance of the thermistor changes about 10 times that of the platinum thermal resistance. By measuring the change in resistance of the thermistor, the temperature change of the measured medium can be known. Thermistor has the advantages of small size, high sensitivity, fast response speed, and high resolution. The shortcomings of a typical thermistor are low linearity and poor stability.
3. Thermocouple temperature sensor Thermocouple temperature measurement is based on the principle of "thermo-EMF effect". The so-called thermoelectromotive force effect means that two different conductors A and B form a closed loop, which is called a hot spot loop. If the temperature of the two junctions of the two conductors is different, there is a certain current in the loop, indicating that an electromotive force is generated in the loop. A commonly used thermocouple is composed of two different wires, and one section of them is welded together, called the "hot end" (usually the measuring end), and placed in the measured medium. The two free ends that are not connected are called cold ends (usually reference ends). Thermocouples are mainly used for the measurement of gas, steam, liquid and other media. They have the characteristics of simple structure, convenient production, wide measurement range, high accuracy, and small thermal inertia. The disadvantages of thermocouple temperature sensors are low sensitivity and poor linearity, and the cold junction requires temperature compensation.
4. Integrated temperature sensor The integrated temperature sensor is made of silicon semiconductor integrated technology, so it is also called a silicon sensor. The integrated temperature sensor came out in the 1980s. It integrates the temperature sensing part, amplifying circuit, driving circuit, signal processing circuit, etc. on a chip, which can complete temperature measurement and analog signal output functions. Compared with other temperature sensors such as thermistors, the integrated temperature sensor has the characteristics of high sensitivity, good linearity, fast response speed and good linearity and consistency. At the same time, it has the characteristics of single function (only measuring temperature), small temperature measurement error, low price, fast response speed, long transmission distance, small size, and low power consumption. It is suitable for long-distance temperature measurement and temperature control without nonlinearity. Calibration, the peripheral circuit is simple. It is currently the most common integrated sensor used at home and abroad. As the production cost of the integrated temperature sensor decreases, it will be widely used in more fields.
Infrared thermometers use infrared rays to measure body temperature, and are mostly divided into contact and non-contact types. The infrared thermometer measures temperature, which is relatively safe and accurate, suitable for use by the elderly, children, hospitals and families.
Infrared thermometer is a measuring instrument that uses the principle of radiation to measure the body temperature of the human body. The infrared sensor it uses only absorbs the infrared rays radiated by the human body without emitting any rays to the outside world, and senses the body temperature of the human body through a non-contact method.
The infrared heat radiation of the human body is focused on the detector, and the detector converts the radiant power into an electric signal, which can be displayed in the unit of temperature after being compensated for the ambient temperature.
Infrared thermometers are divided into contact infrared thermometers and non-contact infrared thermometers:
Contact infrared thermometer. Take an ear thermometer as an example, which is mainly composed of a housing, a temperature probe, a temperature sensor, a PCB circuit, a liquid crystal display, a buzzer, and a battery.
Non-contact infrared thermometer. Taking the forehead thermometer as an example, it is mainly composed of an infrared probe assembly, a main circuit board assembly, an LCD display assembly and a housing assembly.
Infrared thermometers are mainly divided into contact infrared thermometers and non-contact infrared thermometers.
Contact infrared thermometer. The common ones are ear thermometers, forehead thermometers, and multifunctional clinical thermometers. It only takes one second to get an accurate body temperature from the ear. Gently straighten the ear canal when in use, insert the temperature measuring head into the ear canal, press the upper temperature measurement for one second, and then you can read the accurate body temperature with an accuracy of at least one decimal place from the LCD screen, which is safe and guaranteed. , Replace the protective rubber cover when in use to avoid bacterial infection, and it is safe even if the whole family shares it.
Non-contact infrared thermometer. The most common is the forehead thermometer, which can measure the temperature of the human body far away. Just point the probe at the forehead and press the measurement button, and the measurement data can be obtained in only a few seconds, which is very suitable for use by patients with acute and serious illness, the elderly, infants and young children. However, in the early stage of use, users may get several different measurement data because they are not familiar with this operation mode. Generally speaking, the measured maximum value is the desired data. The user will be more satisfied with this kind of thermometer after being familiar with it.
