Distributed temperature sensor.
1.Sensor introduction
1.1 Temperature sensor background
In the human living environment, temperature playing an extremely important role。No matter where you live, engaged in any work, ever-present dealt with temperature under. Since the 18th century, industry since the industrial revolution to whether can master send exhibition has the absolute temperature touch. In metallurgy, steel, petrochemical, cement, glass, medicine industry and so on, can say almost eighty percent of industrial departments have to consider the factors with temperature. Temperature for industrial so important, thus promoting the development of the temperature sensor.
1.2 Temperature sensor development
Major general through three sensor development phase: analog integrated temperature sensor. The sensor is taken with silicon semiconductor integrated workmanship, therefore also called silicon sensor or monolithic integrated temperature sensor. Such sensing instruments have single function (only measuring temperature), temperature measurement error is smaller, price low, fast response, the transmission distance, small volume, micro-consumption electronic etc, suitable for long distance measurement temperature, temperature control, do not need to undertake nonlinear calibration, peripheral circuit is simple. It is currently the most common application at home and abroad anintegratedsensor Typical products have AD590 AD592, TMP17, LM135, etc.jAnalog integrated temperature controller. Analog integrated temperature controller mainly include temperature control switch, programmable temperature controller, a typical product have LM56, AD22105 and MAX6509. Some increase strength type integrated temperature controller (for example TC652/653) also contains the A/D converter and cure good sequence, this process with the intelligent temperature sensor some similarities. But it is not its system, work by micro processing device control, this is the main difference between. Intelligent temperature sensor. intelligent temperature sensor (also called digital temperature degrees sensor) is in the mid 1990s launch. It is microelectronics technology, computer technology and the dynamic testing technology (ATE) crystallization. Intelligent temperature sensor internal contain temperature sensor, A/D converter, signal processormemory (or registers) and interface circuit. Some products still take multiplexer, central control system device (CPU), random access memory (RAM) and read only memory (ROM). Intelligent temperature sensor is characteristic of temperature data and relevant can output the temperature control of the quantity, adaptation various micro controller (MCU);
1.3 Single point and more temperature sensor
The development trend of the temperature sensor. In the 21st century, the temperature sensor is headed in high precision, multi-function, bus, standardization, high reliability and safety, development of virtual sensor and network sensor, research monolithic temperature measuring system and other high-tech direction develop rapidly. Sensors in the application temperature controlling system. Current market exists mainly single point and more two temperature measurement. For single point temperature foundment instrument, mainly adopts the traditional analog integrated temperature sensor, which heat resistance, thermocouple sensors measuring accuracy, high measurement range, and got the general application. This product is temperature measuring range ℃ ~ 200 mostly between 800 ℃, resolution 12th, and least distinguishable temperature in 0.001 ~ 0.01 between. Cabin LED display module, shows ranging from 4 to 16. Some instruments also has memory function, can store several hundred to a few thousand sets of data. This instrument can be very good meet a single user single-point measurement needs. More temperature measurement, relative and single point measurement precision has certain gap, although realized the multi-channel temperature measurement and control, but the price is expensive. In view of the present market situation, proposed this topic can satisfy requirements, scalable and cost-effective single-chip multi-channel temperature measuring system. Through the first temperature sensor DS18B20 acquisition, and then through the C51 SCM processing and displayed on the digital tube, can be collected indoor or a greenhouse around in different locations of the temperature, with four digital tube to display. The first digital pipe display acquisition is which way, which channel. Three digital pipe display after the acquisition channel by temperature, accurate to 0.1 degrees.
2. The system realized and related technologies
2.1.The system is realized
By the whole control system for core AT89C51, using four ways of temperature sensor DS18B20 in production site for distribution area of four different temperature measurement result with the chip checking, collation store and display, and through the button control, temperature will process after theLED digital display to come out, and the software assurance systemanti-interference capacity four DS1820 connected to MCU respectively, this scheme four IO mouth occupy MCU four IO though, but the microcontroller IO mouth under the condition of mouth not shortage by this scheme greatly simplify programming difficulty, shorten the design cycle, also can guarantee the stability of the system. A multipoint connection as shown“1-1”
2.2 .AT89C51 Chip introduction
AT89C51 is a 4K bytes FLASH Memory (Erasable Programmable and FPEROM - FLASH for the campaigns with) low voltage, high-performance CMOS eight microprocessors, commonly known as the microcontroller. AT89C2051 is a 2K bytes with flash memory can be erased programmable read-only memory , SCM can erase read-only memory can be repeated erased 10
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