毕设英文文献部分

Advanced Materials Research Vols. 760-762 (2013) pp 1348-1353 Online available since 2013/Sep/18 at www.scientific.net ? (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.760-762.1348

Study on the preparation and implementation of a new

type digital electronic thermometer1

Pingjun Tao1, Shengzhou Yang2, Yuanzheng Yang1,

Xianchao Chen1and Yeqiu Yu1

1

Faculty of Materials and Energy, Guangdong University of Technology,

Guangzhou 510006, China

2

Shenzhen Yongmen Electronics Technology Co., Ltd., Shenzhen

518031, China pjtao@gdut.edu.cn

Keywords: Quick electronic thermometer; intelligent control; temperature sensor;

quick reaction.

Abstract. Human body temperature, as a manifestation of life activity, is an important physiological parameter of the new supersedes the old. The body temperature not only has physiological significance, but also has important clinical significance, which can be considered as an important index for clinical diagnosis. Based on the NTC temperature sensor as the core, through the whole system framework construction and the software control system design, a quick and accurate intelligent digital electronic thermometer was prepared. Under software control, intelligent temperature measurement is realized. The thermometer not only can accurately register the temperature, also has many functions such as broadcast and logic judgment on temperature, in which, the display module will judge and display the measurement results.

Introduction

The normal body temperature is controlled by the body temperature regulation center, from which heat and cooling process maintain a dynamic balance via neural and body fluid factors, holding body temperature at a relatively constant range. Normal body temperature is a necessary condition for the new supersedes the old of a body and life activities. Body temperature is not only a result of the new supersedes the old of a body, but also one of those objective syndromes of diseases [1]. When pathogenic bacteria invade the body, the body would change in a local area. The neuroendocrine regulation can cause stress reaction, leading to apparently change in body temperature. Through the observation of body temperature, the activities of the important organs as well as the dynamics of the disease can be understood. The accuracy of temperature measurement directly affects the diagnosis, treatment and nursing of diseases [2].

Body temperature is one of the most important objective indexes for disease history collection and data process from clinical medical staff, meanwhile temperature is important physiological parameters acquired relative easily. Accuracy and timeliness of temperature measurement directly affect the diagnosis and treatment of diseases [3].

For conventional glass mercury thermometer, because longer time is required to achieve the thermal equilibrium during temperature measurement, the measurement speed is relatively slow. In addition, the mercury thermometer adopts the refraction

principle, resulting in difficulty of reading data. As the same time, the last number needs to be estimated, and the accuracy is low [4]. The mercury resetting is very inconvenient, and the thermometers are easily broken. The application of mercury thermometers is easy to cause cross infection. At the same time, mercury thermometers contain mercury, easily causing serious pollution to the environment, to which people have payed more attention for a long time [5]. Therefore, the research and development of new type high precision temperature measuring instruments are very urgent. The present paper introduces the design and preparation of an electronic clinical thermometer, which has a positive effect to achieve reliable continuous high precision temperature monitoring and prevent the pollution of the environment.

Working principle

Intelligent electronic thermometers are kinds of typical intelligent instruments, among which the MCUs serve as the core and are combined with other hardware circuit under the control of the software to realize intelligent body temperature measurement [6]. The system hardware consists of six aspects, i.e., temperature sensor, amplifying circuit, A/D conversion circuit, SCM system, liquid crystal display module and the voice chip. The software part includes A/D conversion, digital filter, intelligent function and display program. The working principle is that, via the temperature sensor, the temperature signals are converted into electric signals, then they are put into the amplifier to meet the requirements of A/D converter. And then through the A/D converter, the enlarged electronic signals are converted into the digital signal under the control of A/D converter program.

This signal would be sent to MCU, within which through the software function of microcontroller, digital filtering, linearization processing, data storage, logic judgment are achieved, so as to realize the corresponding intelligent function. The final body temperature measurement results will be sent into the liquid crystal display module. Under the control of display program, the display module displays the temperature results measured, including the temperature data and Chinese characters. At the same time the voice chip starts to broadcast under the program control. So the various temperature measurement operations tend to be more intelligent and humanized [6].

Choice of temperature sensor

According to the relationship between temperature and a certain macroscopic physical parameter, as well as their calibrations, temperature measurement can be achieved. As for the conventional temperature measurement method, thermocouple, thermal resistance or platinum resistance temperature sensor is commonly used as a temperature sensing device. Through the potential difference between either ends of the sensor, temperature value can be obtained indirectly [7,8]. Linear NTC temperature sensor is a temperature voltage conversion device. With the good linearity, NTC temperature sensor overcomes the problem of nonlinear in traditional temperature sensor, which has plagued instrument design personnel for a long time. The NTC temperature sensor adopted in present paper was produced by Shenzhen Yongmen Electronics Technology Co., Ltd., of which, the variation range of thermal resistor: 102~107 ?, the temperature coefficient:-2%~-6.5%, linearity: ± 0.5%, stability: ≤ ± 0.05 ℃/year, temperature coefficient S: -2.4mV/ ℃. The functional block diagram of temperature sensor is shown in Fig.1.

Working principle

Intelligent electronic thermometers are kinds of typical intelligent instruments, among which the MCUs serve as the core and are combined with other hardware circuit under the control of the software to realize intelligent body temperature measurement [6]. The system hardware consists of six aspects, i.e., temperature sensor, amplifying circuit, A/D conversion circuit, SCM system, liquid crystal display module and the voice chip. The software part includes A/D conversion, digital filter, intelligent function and display program. The working principle is that, via the temperature sensor, the temperature signals are converted into electric signals, then they are put into the amplifier to meet the requirements of A/D converter. And then through the A/D converter, the enlarged electronic signals are converted into the digital signal under the control of A/D converter program. This signal would be sent to MCU, within which through the software function of microcontroller, digital filtering, linearization processing, data storage, logic judgment are achieved, so as to realize the corresponding intelligent function. The final body temperature measurement results will be sent into the liquid crystal display module. Under the control of display program, the display module displays the temperature results measured, including the temperature data and Chinese characters. At the same time thev oice chip starts to broadcast under the program control. So the various temperature measurement operations tend to be more intelligent and humanized [6].

Choice of temperature sensor

According to the relationship between temperature and a certain macroscopic physical par- ameter, as well as their calibrations, temperature measurement can be achieved. As for the conventional temperature measurement method, thermocouple, thermal resistance or plat- inum resistance temperature sensor is commonly used as a temperature sensing device. Th- rough the potential

difference between either ends of the sensor, temperature value can be obtained indirectly [7,8]. Linear NTC temperature sensor is a temperature voltage convers- ion device. With the good linearity, NTC temperature sensor overcomes the problem of no- nlinear in traditional temperature sensor, which has plagued instrument design personnel for a long time. The NTC temperature sensor adopted in present paper was produced by Shenzhen Yongmen Electronics Technology Co., Ltd., of which, the variation range of thermal resistor: 102~107 ?, the temperature coefficient: -2%~-6.5%, linearity: ± 0.5%, stability: ≤ ± 0.05 ℃/year, temperature coefficient S: -2.4mV/ ℃. The functional block di- agram of temperature sensor is shown in Fig.1.

Design of digital thermometer

The hardware system structure of the thermometer mainly includes SCM core system, oscillation circuit module, display module, communication module and power supply module [9]. Micro controller has adopted a new generation strengthened-type SCM.EEPROM, 16 digit iner- valometer/counter and programmable watchdog circuit are embedded in SCM, which has greatly simplified the system design, meanwhile improved the system’s reliability and stability [10]. In order to achieve the temperature and frequency conversion, the NTC thermistor and intervalometer are used to form a multiple harmonic oscillation circuit The intervalometer is a versatile digital