Forehead thermometer solution development

The forehead temperature gun (infrared thermometer) is designed to measure the human body's forehead temperature and is very simple and convenient to use. It can accurately measure temperature in 1 second, without laser point, which avoids potential damage to the eyes. It does not need to come into contact with human skin to avoid cross-infection. One-click temperature measurement can check for influenza. It is suitable for home users, hotels, libraries, large enterprises and institutions, and can also be used in comprehensive places such as hospitals, schools, customs, airports, etc. It can also be provided to medical personnel for use in clinics.

1. Use of forehead thermometer

(1) Human body temperature measurement: Accurately measure human body temperature, replacing the traditional mercury thermometer. Women who are ready to have children can use an infrared thermometer (forehead thermometer) to monitor basal body temperature at any time, record body temperature during ovulation, choose the right time to conceive, and measure temperature to determine pregnancy, etc. Of course, the most important thing is to observe whether your body temperature is abnormal at any time to avoid influenza infection, swine flu, etc.

(2) Skin temperature measurement: Measure the surface temperature of the human skin. For example, it can be used to measure the surface temperature of the skin during re-implantation surgery of severed limbs.

(3) Object temperature measurement: Measure the surface temperature of an object, such as the surface temperature of a tea cup.

(4) Liquid temperature measurement: Measure the temperature of the liquid, such as the temperature of the baby's bath water. Measure the water temperature when the baby is taking a bath, so you no longer have to worry about it getting cold or burning; 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.

2. Working principle of forehead thermometer

Any object above absolute zero (-273°C) will emit infrared rays outward, and the forehead thermometer receives infrared rays through the sensor to obtain the sensed temperature data. The principle of the forehead temperature gun is to accurately convert the voltage signal output by the pyroelectric sensor into a temperature value and display it. The key device is the pyroelectric sensor, which is also called a human body infrared sensor. Although the measurement principle is not complicated, there are still five major technical difficulties in the finished forehead thermometer.

(1) The output signal amplitude of the sensor is small, and the measured voltage is as low as 2μV. (2) The output signal amplitude of the sensor will be affected by the ambient temperature, and ambient temperature compensation is required. (3) The traditional forehead thermometer solution is not open to the public, and there are few engineers with relevant experience. (4) A good forehead thermometer requires comprehensive knowledge of electronics, optics, and heat. (5) Design and production require sophisticated experimental testing environment (constant temperature environment) and equipment (constant temperature bath).

2.1 Principle of infrared temperature measurement

When an object is above absolute zero, because of the movement of its internal charged particles, it radiates energy in the form of electromagnetic waves of different wavelengths. The wavelengths involve ultraviolet, visible, and infrared light regions, but 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 the wavelength have a very close relationship with its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately determined, which is the objective basis for infrared radiation temperature measurement.

2.2 Working process of infrared thermometer

The 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 ray radiated by the measured object first enters the optical system of the thermometer, and then the optical system converges the incoming infrared rays to make the energy more concentrated; the gathered infrared rays are input into the photodetector, and 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 forehead thermometer

Place the temperature measuring probe on the bridge of the nose, the middle part of the eyes is the radiation source closest to normal body temperature relative to the body surface temperature, and place the forehead temperature gun at a distance of 5-6cm to measure the temperature. The accuracy is ±0.3. It is not recommended for medical use, but it can be used for rapid and non-contact safety investigation of influenza. Those who call the police can be diagnosed in time by the hospital for prevention and treatment.

The normal body temperature of the human body is between 36 and 37°C on average), exceeding 37.1°C is fever, 37.3-38°C is low-grade fever, and 38.1-40°C is high fever. Above 40℃, life is in danger at any time.

4. What is the normal body temperature for a forehead thermometer?

The normal value of forehead temperature is 35.8 to 37.8 degrees Celsius. The forehead thermometer uses a built-in sensor to measure the infrared energy radiated from the forehead, and then it can accurately measure the surface temperature of the forehead. Because the forehead thermometer has the advantages of simplicity, speed and no cross-infection, it is more suitable for use in places with large flow of people such as airports, stations and shopping malls.

To ensure the accuracy of the results when measuring body temperature, avoid hair and use alcohol to clean away oil and dirt from the skin. Select the middle of the forehead and keep a distance of 3 to 5 cm. It is recommended to measure multiple times and choose the highest one as the result. However, because the forehead is exposed skin, it is greatly affected by the outside temperature. You can choose parts such as the wrist and neck, and the results will be more realistic and accurate.

5. Forehead thermometer design

Body temperature is the most basic physiological parameter of the human body. It is very important for daily care and disease detection. Many diseases can be predicted by changes in body temperature. Infrared temperature measurement provides a fast and non-contact measurement method for measuring human body temperature, and solves the problem of contact in traditional temperature measurement. It has the characteristics of fast response, high measurement accuracy, wide measurement range and simultaneous measurement of target temperature and ambient temperature. . Non-contact infrared thermometers work well for specific groups of people, such as children or the elderly. Therefore, the design of the forehead thermometer has important practical significance.

5.1 Overall plan idea of forehead thermometer

As the control center of the entire system, the SPCE061A streamlined development board is responsible for controlling and starting temperature measurement, receiving measurement data, calculating temperature values, controlling the playback and display process according to the obtained key values, and playing temperature values through the audio output channel at the same time; the infrared temperature measurement module is responsible for temperature The measurement, collection, and the collected data are transmitted to the SPCE061A single-chip microcomputer 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, start the infrared temperature measurement module through IOA13 for temperature measurement, read the clock of the infrared temperature measurement module through IOA14, and judge the negative edge of the clock , read the measurement data through IOA15.

5.2 Forehead thermometer system software design

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 scanning program to scan the keyboard, and judge which program branch to execute according to the key value. If the first key (K1) is pressed, call the measurement temperature program to measure, and judge whether the target temperature is measured correctly, otherwise continue to measure until the correct data is measured; if it is, it will play and display the target temperature value. Then call the measurement temperature program to measure and judge whether the ambient temperature is measured correctly, otherwise continue to measure until the correct data is measured; if it is, it will play and display the ambient temperature value. If the second key (K2) is pressed, the temperature measurement program is called to measure, and it is judged whether the target temperature is measured correctly, otherwise, continue to measure until the correct data is measured; if it is, it will play and display the temperature value. If the third key (K3) is pressed, call the measurement temperature program to measure and judge whether the ambient temperature is measured correctly, otherwise continue to measure until the correct data is measured; if it is, it will play and display the temperature value; if no keyboard is pressed, then Go back and rescan the keyboard.

5.3 Overall test of forehead thermometer system

First, confirm that the short-circuit sleeve on the S5 has been unplugged, check whether the connections of various parts of the circuit are correct, and then turn on the power of the battery box after confirming that they are correct. Point the probe of the infrared temperature measurement module at the measurement target, and the measurement is controlled by K1~K3 of the LED keyboard module, where K1 measures and broadcasts the target temperature and ambient temperature, K2 measures and broadcasts the target temperature, and K3 measures and broadcasts ambient temperature. After testing, the measurement accuracy of the forehead 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 terms of measurement distance, due to the deviation of manual alignment of the measurement target during measurement, the accuracy of long-distance measurement will be reduced, but the degree of reduction is within the allowable range.

Summarize

The operation of this system is very simple. Although it is named "forehead temperature gun", it does not mean that the temperature can only be measured from the forehead, but can also measure the surface temperature of any object with infrared emission. Measuring the body temperature is a vivid metaphor. The system uses the SPCE061A simplified development board as the control center of the whole system, combined with the infrared temperature measurement module, keyboard and LED display module, to realize the non-contact infrared measurement and voice broadcast of the temperature, and the measurement accuracy can reach two digits after the decimal point. It meets the design requirements and has certain practical value.

The above are the details of the forehead thermometer solution introduced to you by Shenzhen Zuchuang Microelectronics Co., Ltd. If you have electronic function development needs for ear thermometers, you can rest assured to entrust them to us. We have rich experience in customized development of electronic products, and can evaluate the development cycle and IC price as soon as possible, and can also calculate PCBA quotations. We are a number of chip agents at home and abroad: Songhan, Yingguang, Jieli, Ankai, Quanzhi, realtek, with MCU, voice IC, Bluetooth IC and module, wifi module. Our development capabilities cover PCB design, single-chip microcomputer development, Bluetooth technology development, software customization development, APP customization development, WeChat official account development and other hardware and software design. It can also undertake the research and development of smart electronic products, the design of household appliances, the development of beauty equipment, the development of Internet of Things applications, the design of smart home solutions, the development of TWS earphones, the development of Bluetooth earphone speakers, the development of children's toys, and the development of electronic education products.