外文翻译---基于单片机的多功能温度检测系统的设计(5)

In the traditional analog signal distance temperature measuring system, need good solve lead error compensation, multi-point measurement error and amplifying circuit switching technologies such as zero drift error problem, can achieve high measuring accuracy. Another general monitoring site of the electromagnetic environment is very bad, all kinds of jamming signal is stronger, the simulated temperature signal interference and vulnerable to produce measurement error and measuring precision [5]. Therefore, in temperature measuring system, the strong anti-jamming capability of the new digital temperature sensor is the most effective to solve these problems, compared with other temperature sensor DSl820 has the following features:

(1) the unique singleline interface way. DSl820 in connection with the microprocessor only need one interface to implement line DSl820 microprocessors and two-way communication. (2) more function simplifies distributed temperature detection application. (3) DSl820 in use without any peripheral devices. (4) power, voltage range data available from 3.0 V to 5.5 V. (5) can measure temperature range from - 55 degrees c + + to 125, incremental value 0. 5 ° c, Fahrenheit temperature range from - 67 to + 257, incremental value 0.9. (6) support multi-point network function. Multiple DS1820 can pick on the same bus and, more temperature measurement. (7) 9 temperature resolution. Measuring results in nine serial transmission way the digital quantity. (8) user can set temperature alarm threshold. (9) have super temperature search function.

①.DSl8B20 principle of work

The internal structure of DS18B20 DSl8B20 temperature measurement principle diagram shown in figure 3.2. Low temperature coefficient graph oscillation frequency vibration product temperature is used to produce with fixed frequency, pulse signal to counter l. High temperature coefficient crystals temperature-dependent its oscillation frequency change significantly. The signal generated as the counter 2 input pulses. Counter 1, 2 and temperature registers are counter in - 55 degrees preset corresponding a base value. Counter l to low temperature coefficient of the pulse signal generated crystals, when the counter for subtraction counting the preset value reduced to 1, when the temperature counter O value will add l, counter the preset value will be l man again, to counter the l start low temperature coefficient of crystal oscillator pulse signal, so cycle count until the counter 2, stop counting to O accumulative temperature, temperature of the register for the register is measured values. Figure 3.2 accumulative used for the slope compensation and fixed temperature measurement, the output of the process of nonlinear correction is less than the preset value counter l.

②.AT89S52 interface mode and DS18B20

Chip DS18B20 and the connection has two kinds: namely parasitic power and external power supply mode.

Parasitic power way: in the parasitic power supply mode, the signal from the single chip DS18B20 in line drawing energy during the high level in the DQ energy stored in

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