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1、华北科技学院毕业设计（论文） 基于AT89S52单片机的风速测量仪的设计综述风，特别是井下安全生产中具有重要参考意义，作为气象环境中最活跃的因素，对战争的胜败，武器性能的发挥有着举足轻重的影响风能的利用，也要求人们对风速资源进行长时间的准确监测。当前，风速测量的仪器主要有热线式、热膜式、以及风杯式三种。这几种原理的风速仪测量精度低、范围小、测量周期长、持续工作时间短，且测量结果易受外部环境因素的影响。因此不能满足高效、快速、准确的现代化军事和长时间工作、智能化数据处理的风场监测的需求。本设计采用压电式超声波换能器，使用AT89S52单片机作为控制器，完成了超声波风速测量仪的软硬件设计。采用汇编
2、语言编程的方法，实现了测量结果的计算和显示。设计完成后能做到，LED数码显示清晰稳定，测量结果稳定可靠，测距仪最大误差不超过0.05m/s。系统硬件电路的设计 硬件电路的设计主要包括单片机系统及显示电路、键盘，温度补偿电路，超声波发射电路和超声波检测接收电路三部分。单片机采用89S52或其兼容系列。采用11.0592MHz高精度的晶振，以获得较稳定时钟频率，减小测量误差。系统采用555定时器产生145kHz的方波信号，利用计数T1口监测超声波接收电路整形滤波后输出的返回信号。显示电路采用简单实用的4位共阴极LED数码管，段码用电阻器驱动，位码用PNP三极管8550驱动。超声波发射电路发射电路主
3、要由555定时器，74LS123构成的单稳态触发电路、放大环节，和超声波发射换能器T构成，LM555多谐振荡器端口3输出的145kHz的方波信号一路经触发电路，放大电路后送到超声波换能器两端，可以提高超声波的发射强度。输出端采用加入耦合电容C4，用以提高发射驱动能力。上位电阻R6一方面可以提高三极管的放大输出能力，另一方面可以增加超声波换能器的阻尼效果，缩短其自由振荡时间。压电式超声波换能器是利用压电晶体的谐振来工作的 。超声波换能器内部结构在下文中有介绍，它有两个压电晶片和一个换能板。当它的两极外加脉冲信号，其频率等于压电晶片的固有振荡频率时，压电晶片会发生共振，并带动共振板振动产生超声波，
4、这时它就是一个超声波发生器；反之，如果两电极间未外加电压，当共振板接收到超声波时，将压迫压电晶片作振动，将机械能转换为电信号，这时它就成为超声波接收换能器了。超声波发射换能器与接收换能器在结构上稍有不同，使用时应分清器件上的标志T和R。超声波检测接收电路压电式超声波换能器S将收到的超声信号转换成电信号，并经R7、R8、R9、C5、C6和1/4 LM324组成的选频放大电路放大后，送检波电路Dl、C7、R10进行包络检波，检出涡街信号。涡街信号在电压比较器和RC滤波电路构成的整形滤波环节中与输入的基准电压1/2Vcc作比较，被整形为与风速成正比的矩形波，信号周期随检波信号变化而变化。超声波风速测
5、量仪的软件设计主要由主程序，超声波接收程序及显示，键盘子程序，温度补偿子程序组成。我们知道汇编语言程序则具有较高的效率且容易精细计算程序运行的时间，而超声波风速测量仪的程序要求精细计算（单位时间内的整形完成的超声波矩形方波个数时），所以控制程序采用汇编语言混合编程。超声波测距仪的算法设计 超声波风速传感器是利用穿过空气的超声波被旋涡调制，从已调波中检出旋涡频率来测定风速的。F、S为一对谐振频率相同的超声波换能器，F为发射换能器，发射145 kHz等幅超声波；S为接收换能器，接收被旋涡调制了的声波。当无旋涡时，接收换能器S接收到等幅波信号；有旋涡时，由于旋涡内部的压力梯度和旋涡的旋转运动，导致了
6、超声波的折射、反射和吸收效应，使接收到的信号幅度减小。旋涡通过声束后，接收到的信号又恢复常态。因此，超声波幅度变化频率与旋涡的频率一致，从接收换能器上检测出超声波束幅度变化次数即可测得风速值。基本计算公式为：f旋涡频率，Hz ；v气流速度，ms ；d旋涡发生体直径，mm；St斯特拉哈尔系数(雷诺数在20050 000范围内，St为常数)。超声波旋涡式风速传感器与其它形式的风速传感器相比具有如下优点：(1)无可动部件，无机械磨损，性能稳定，使用寿命长；(2)输出本身就是与风速成线性关系的脉冲频率信号，没有零点漂移，且敏感元件灵敏度变化不会直接影响输出，测量精度高；(3)输出信号不受流体特性(温度
7、、湿度、压力、成份、密度、粘度、矿尘等)影响。此类传感器在煤矿安全监控系统中有着广泛的应用前景。关键词：风速测量；卡曼涡街；单片机AT89C52；温度补偿IThe Design of Ultrasonic Wind Meter Based on SCMSummary: Wind, especially mine safety has important reference value, as the meteorological environment, the most active factor, the victory of the war, weapons performance to
8、 play a decisive effect on the use of wind energy, wind resources also requires that there be lengthyaccurate monitoring.At present, the wind speed measurement apparatus main hot wire, hot-film, and the wind cup of three.This principle of wind speed measured several low precision, range of small, me
9、asuring cycle is long, continuous working hours, and the measurement results vulnerable to external environmental factors.Can not meet the efficient, rapid and accurate modern military and long working hours, intelligent data processing, the demand for wind monitoring. This design uses piezoelectric
10、 ultrasonic transducer, using AT89S52 MCU as controller to complete the ultrasonic velocity meter hardware and software design.Assembly language programming method used to achieve the measurement results of the calculation and display.Design can be completed, LED digital display clear and stable, re
11、liable measurements, range finder error is less than 0.05m / s. System hardware design The hardware design includes single chip systems and display circuit, keyboard, temperature compensation circuit, ultrasonic transmitter and ultrasonic receiver circuit of three parts.Microcontroller 89S52 or comp
12、atible with Series.11.0592MHz crystal with high precision in order to obtain a stable clock frequency, reducing measurement error.System uses the 555 timer 145kHz square wave signal generated using the count of T1 port monitoring ultrasonic receiver circuit to return plastic filtered output signal.D
13、isplay circuit using a simple and practical four common cathode LED digital tubes, with 74HC244 driver code segment, bit code with the PNP transistor 8550 drives. Ultrasonic transmitter Transmitter mainly by the 555 timer, 74LS123 monostable trigger circuit formed, enlarged links, and ultrasonic emi
14、ssion transducer T form, LM555 Multivibrator Port 3 output 145kHz square wave signal all the way through trigger circuit, amplifier circuitultrasonic transducer is sent to both ends, can increase the emission intensity ultrasound.By adding the output coupling capacitor C4, launching drives to increa
15、se capacity.Upper resistor R6 on the one hand can increase the output capacity of the amplification transistor, on the other hand can increase the ultrasonic transducer damping effect, shorten the time of its free oscillations.Piezoelectric ultrasonic transducers is the use of piezoelectric crystal
16、resonance to the work.The internal structure of ultrasonic transducers are introduced below, it has two chips, and a piezoelectric transducer plate.When its poles plus pulse signal, the frequency is equal to the natural oscillation frequency of the piezoelectric chip, the piezoelectric resonance occurs, and promote the vibration of ultrasonic resonance board, then it is an ultrasonic generator; the
