【作者】 任启明；

【导师】 陈荣保；

【作者基本信息】 合肥工业大学 ， 检测技术与自动化装置， 2008， 硕士

【摘要】 作为测量精度较高、压力损失较小的新型流量仪表,涡街流量计已广泛应用于液体、气体和蒸汽的流量测量。近年来对涡街流量计的研究显示,信号频率越高,强度越大,噪声越小,而低频段的信号,噪声干扰较为严重,所以对信号低频段的分析是重要的。而在实际应用中仪表将长期工作在无外界电源的环境下,所以对功耗要求比较高。本论文从这两方面着手,设计了一款低功耗智能涡街流量计。软件算法采用变采样点数的FFT算法,由于单片机计算FFT耗时较多,故对于不同频率的信号作不同点数的FFT运算,以达到精度和实时性的较好结合。所以针对涡街流量信号的特点,在测定的频率范围内采用变换采样点数的FFT运算,并由实时测定和计算出的频率区域确定下次的采样点数。通过数据验证和误差分析,证明了变换采样点数的FFT运算可行,加强了流量计的抑制噪声能力,同时最大限度满足了实时性的要求,从而增加了流量计的性价比。功耗是仪表设计的重要参数,论文采用TI公司生产的超低功耗的16位单片机MSP430F149作为主控制器,单片机对各传感器(涡街传感器、温度传感器、压力传感器)的信号进行采集、分析、计算,并进行补偿。硬件中各部分均采用低功耗设计,各模块的芯片均选用功耗最低的。并且采用EEPROM和日历时钟芯片,将日历时钟和流体的流量结合在一起,便于流量数据的查询。流量计运算结果存入EEPROM,并通过串口输出,也可选择通过液晶显示。更多还原

【Abstract】 The vortex flowmeter has been widely applied in the liquid, gas and steam flow measurement because of high measuring accuracy and small pressure loss. Recently the research for vortex flowmeter demonstrated that if the signal’s frequency is higher, the intensity is larger and noise is less, but the noise disturbance is very serious of the low frequency band’s signal, so the analysis of the low frequency band’s signal is important. As the flowmeter works chronically under the non-power condition, the size of power is an important parameter. This paper introduced a design of low-power intelligent vortex flowmeter in above two aspects.In software algorithm, the sampling points for FFT calculation could be changed. Because FFT caculation of MCU is time-consuming, different points FFT operation was made regard to different frequency’s signal. This algorithm make the flowmeter reached the requirements of the precision and the real-time. So for the characteristic of the vortex signal, the FFT calculated with selected sampling points within the measured frequency ranges, then determined the next sampling points on the result. The arithmetic is feasible by the error analyzing and data validating. And this technique imprvoe the flowmeter’s capability of noise suppress and match real-time request. Thereby it is a high cost-performance.The size of power is an important parameter. 16 bit MCU MSP430F149 producted by TI was used as main-controller in this design. The MCU had carried on the sampling, analysis, culculation to the signals of various sensors, then made compensation for them. Low-power design was applied in hardware parts. EEPROM and real-time chip was choosed in this design, which combined with the flow of liquid,and this design will make inquiring the flow data conveniently. The results of caculation is stored in EEPROM, and it also can be outputted through serial port and display on the LCD if necessary.更多还原