The design and development of the front temperature gun
The forehead temperature gun (infrared thermometer) is designed for measuring the human body forehead temperature reference, which is very simple and convenient to use. Accurate temperature measurement in 1 second, no laser spot, avoid potential damage to eyes, no need to contact human skin, avoid cross infection, one-click temperature measurement, and check for flu. It is suitable for home users, hotels, libraries, large enterprises and institutions, and can also be used in hospitals, schools, customs, airports and other comprehensive places, and can also be provided to medical personnel for use in clinics.
1. Use of the front temperature gun
(1) Human body temperature measurement: accurate measurement of human body temperature, replacing the traditional mercury thermometer. Women who want to have a child can use an infrared thermometer (frontal temperature gun) to monitor the basal body temperature at any time, record the body temperature during ovulation, and choose the right time to conceive, and also measure the temperature to judge pregnancy and so on. Of course, the most important thing is to always observe whether your body temperature is abnormal, to avoid flu infection, to prevent swine flu, etc.
(2) Skin temperature measurement: To measure the surface temperature of the human skin, for example, it can be used for amputation and re-implantation.
(3) Object temperature measurement: measuring the surface temperature of an object, for example, it can be used to measure the temperature of the surface of a tea cup.
(4) Liquid temperature measurement: measure the temperature of the liquid, such as the temperature of the baby’s bath water. When the baby takes a bath, measure the water temperature, and no longer worry about being cold or hot; you can also measure the water temperature of the milk bottle to facilitate the preparation of Baby’s milk powder .
(5) Room temperature can be measured.
Second, the working principle of the front temperature gun
Any object above the absolute zero (-273 ℃) will emit infrared rays, and the forehead gun receives infrared rays through the sensor to obtain the temperature data. The principle of the frontal temperature gun is to accurately convert the voltage signal output by the pyroelectric sensor into a temperature value and display it. The key component is the pyroelectric sensor, which has also become the infrared sensor of the human body. Although the measuring principle is not complicated, there are still five technical difficulties in the finished forehead temperature gun.
(1) The amplitude of the sensor output signal is small, and the measured voltage is as low as 2μV. (2) The amplitude of the sensor output signal will be affected by the ambient temperature, and ambient temperature compensation is required. (3) The traditional program of temperature gun is not open to the outside world, and there are few engineers with relevant experience. (4) A comprehensive knowledge of electronics, optics, and heat is required for a good temperature gun. (5) Design and production require precise experimental testing environment (constant temperature environment) and instruments and equipment (constant temperature bath).
2.1 Infrared temperature measurement principle
When the object is above absolute zero, because of the movement of the charged particles inside, it radiates energy in the form of electromagnetic waves of different wavelengths. The wavelength involves the ultraviolet, visible, and infrared regions, but it is mainly in the near infrared of 0.76~3μm, 3~6μm. Mid infrared, 6~15μm far infrared region. The size of the infrared radiation energy of an object and its distribution according to wavelength have a very close relationship with its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, it can accurately determine its surface temperature, which is the objective of infrared radiation temperature measurement.
2.2 Working process of infrared thermometer
Infrared thermometer is composed of optical system, photoelectric detector, signal amplifier, signal processing, display output and other parts. The optical system collects the target infrared radiation energy in its field of view, and the size of the field of view is determined by the optical parts and position of the thermometer. The infrared radiated by the measured object first enters the optical system of the thermometer, and then the incident infrared rays are collected by the optical system to make the energy more concentrated; the collected infrared rays are input into the photoelectric detector. The key component of the detector is the infrared sensor. Its task is to convert the optical signal into an electrical signal; the electrical signal output from the photodetector is converted into the temperature value of the measured target after being corrected by the amplifier and the signal processing circuit according to the internal algorithm of the instrument and the target emissivity.
3. How to use the front temperature gun
Place the temperature probe on the bridge of the nose. The middle part of the two eyes is the radioactive source closest to the normal body temperature relative to the body surface temperature. Place the frontal temperature gun at a distance of 5-6 cm to measure the temperature. The accuracy is ±0.3, it is not recommended for medical use, but it can be used for rapid flu, non-contact safety inspection. The alarm can be diagnosed and promptly diagnosed by the hospital for prevention and treatment.
The normal body temperature of the human body is between 36 and 37°C). If it exceeds 37.1°C, it means fever, 37.3-38°C means low fever, and 38.1-40°C means high fever. There is danger of life at any time above 40℃.
4. What is the normal body temperature of the forehead gun?
The normal value of the frontal temperature is 35.8 to 37.8 degrees Celsius. The forehead temperature gun uses the built-in sensor to measure the infrared energy radiated from the forehead, and can accurately measure the surface temperature of the forehead. The frontal temperature gun has the advantages of simplicity, single speed and no cross-infection, and is more suitable for use in places with large passenger flow such as airports, stations and shopping malls.
In order to ensure the accuracy of the results when measuring body temperature, avoid hair and use alcohol to clean the skin of grease and dirt. Select the middle of the forehead and keep a distance of 3 to 5 cm. It is recommended to measure multiple times and select the highest one as the result. However, because the forehead is exposed skin, it is greatly affected by the outside temperature. You can choose the wrist and neck and other parts, the result will be more true and accurate.
V. Design of the front temperature gun
Body temperature is the most basic physiological parameter of the human body. It is very important for daily care and condition detection. There are many diseases that can be predicted by changes in body temperature. Infrared temperature measurement provides a fast, non-contact measurement method for measuring human body temperature, which solves the problem of contact in traditional temperature measurement. It has the characteristics of fast response speed, high measurement accuracy, wide measurement range, and simultaneous measurement of target temperature and ambient temperature. . Non-contact infrared thermometers are very effective for specific people, such as children or the elderly. Therefore, the design of the front temperature gun has important practical significance.
5.1 The overall plan of the temperature gun
The SPCE061A streamlined development board is the control center of the entire system. It is responsible for starting temperature measurement, receiving measurement data, calculating temperature values, and controlling the playback display process according to the obtained key value. At the same time, the temperature value is played through the audio output channel; the infrared temperature measurement module is responsible for temperature The measurement, collection, and transmission of the collected data to the SPCE061A microcontroller through the data port; the keyboard in the LED keyboard module controls the temperature display and playback, and the digital tube displays the temperature value. SPCE061A judges whether to perform temperature measurement according to the key value input by the LED keyboard module. If temperature measurement is required, the infrared temperature measurement module is started through IOA13 to perform temperature measurement, and the clock of the infrared temperature measurement module is read through IOA14 to determine the negative edge of the clock , Read measurement data through IOA15. The block diagram of the front temperature gun system is shown in Figure 1.
5.2 Software design of front temperature gun system
The main program flow chart is shown in Figure 2. Initialize the infrared temperature measurement module and initialize the keyboard; enter the main program loop, call the keyboard scan program to scan the keyboard, and determine which program branch to execute based on the key value. If the first key (K1) is pressed, call the temperature measurement program to determine whether the target temperature is correctly measured, otherwise continue to measure until the correct data is measured; if yes, play and display the target temperature value. Then call the measurement temperature program to determine whether the ambient temperature is correctly measured, otherwise continue to measure until the correct data is measured; if yes, play and display the ambient temperature value. If the second key (K2) is pressed, the temperature measurement program is called to determine whether the target temperature is correctly measured, otherwise continue to measure until the correct data is measured; if yes, play and display the temperature value. If the third key (K3) is pressed, the temperature measurement program is called to determine whether the ambient temperature is correctly measured, otherwise continue to measure until the correct data is measured; if yes, play and display the temperature value; if no keyboard is pressed, then Return to rescan the keyboard.
5.3 Overall test of the temperature gun system
First confirm that the short-circuit sleeve on S5 has been unplugged, check whether the connection of each part of the circuit is correct, and turn on the power of the battery box after confirming that it is correct. Align the probe of the infrared temperature measurement module to the measurement target, and control the measurement by K1～K3 of the LED keyboard module, where K1 is the measurement and broadcast target temperature and ambient temperature, K2 is the measurement and broadcast target temperature, and K3 is the measurement and broadcast report Ambient temperature. After testing, the measurement accuracy of the temperature gun system can reach two digits after the decimal point, which meets the design requirements, and the voice broadcast function can also work normally. In the measurement distance, since there will be a certain deviation when manually aligning the measurement target during measurement, the accuracy of long-distance measurement will be reduced, but the degree of reduction is within the allowable range.
to sum up
The operation of this system is very simple. Although it is named "forehead gun", it does not mean that it can only measure the temperature from the forehead. It can also measure the surface temperature of any object with infrared emission. Measure the body temperature of the human body and make a vivid analogy. The system uses the SPCE061A streamlined development board as the control center of the entire system. It combines infrared temperature measurement module, keyboard and LED display module to realize non-contact infrared measurement and voice broadcast of temperature. The measurement accuracy can reach two digits after the decimal point. It meets the design requirements and has certain practical value.