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双发双收声波测井仪地面部分的主要功能是:按一定的时序产生一系列控制信号,控制下井仪发射探头的交替发射;接收井下传输来的信号,经处理后得到声波时差。指令发生电路的主要功能是对ΔT计数和缓存、刻度计数、跟踪延迟、时差比较等电路作出时序上的控制。本设计根据已有的指令时序图来设计电路原理。整个时序由一个时钟信号同步,时钟信号由555定时器及外围电路构成的多谐振荡器组成,输出分三级频率可调的方波(地面同步信号)。将时钟信号接入74LS74双D触发器进行二分频来产生上控方波(上升沿触发)。地面同步信号经三路CD4538集成电路构成的单稳态电路(下降沿触发)输出脉宽均为5 ms的脉冲信号。用仿真软件multisim 10.0进行仿真,得到电路参数与波形,与时序要求波形一致,最后连接电路并进行了调试。
The main functions of the ground part of the dual-transmit and receive acoustic logging instrument are: generating a series of control signals according to a certain timing to control the alternate transmission of the transmitting probe of the downhole instrument; receiving the signal transmitted from the downhole and processing to obtain the acoustic time difference. The main function of the instruction generating circuit is to make the timing control on the circuits such as ΔT counting and buffering, scale counting, tracking delay and time difference comparison. The design according to the existing instruction timing diagram to design the circuit principle. The whole sequence is synchronized by a clock signal. The clock signal consists of a multivibrator composed of a 555 timer and a peripheral circuit, and the output is divided into three levels of square wave (ground synchronous signal) with adjustable frequency. The clock signal access 74LS74 double D flip-flop to generate a square wave on the control (rising edge trigger). The ground synchronization signal is composed of three CD4538 integrated circuit monostable (falling edge trigger) output pulse width of 5 ms pulse signal. Simulation with multisim 10.0 software to get the circuit parameters and waveforms, waveform and timing requirements consistent, and finally connected to the circuit and debug.