微流量智能型电磁流量计及LS旋转流量计超低功耗设计的研究

【作者】 胡俭波；

【导师】 宋开臣；

【作者基本信息】 浙江大学 ， 机械电子工程， 2002， 硕士

【摘要】 从流量计在工业上开始应用到现在，工业生产对流量计提出了两种发展途径：一是向高精准度、高性能仪表发展；另一个是向小型轻量、安装使用简便、性能适中、价格便宜的普及型方向发展。 本文主要由两个部分组成： 第一部分：微流量智能型电磁流量计的研究 本部分就流量计发展的第一个方向设计出高性能、高精确度的智能型微流量电磁流量计。 文中首先分析了用电磁法测量微流量时比较难测量的原因。根据分析结果，在流量计传感部分采用矩形测量导管来代替传统的圆形测量导管产生磁感应电动势。接着对矩形测量导管进行建模，并在流体流经矩形测量导管时产生感应电动势的大小、流体在测量导管中的压力损失和传感器内阻的大小对输出信号的影响等几个方面与圆形测量导管进行比较后得出采用矩形测量导管完全能够有效地完成微流量的测量。这就为在微流量条件下采用电磁法进行测量建立了理论基础。 其次，在电流励磁部分分析了传统的采用50Hz交流电励磁法和方波励磁法的优、缺点，提出了利用微控制器实现频率可调的低频正弦波电流励磁方法。相对于50Hz交流励磁，这种励磁方法可以采用更低的频率来对微流量的磁路进行励磁，一方面可以完全消除工频干扰，另一方面可以极大地减小正交干扰；相对于方波励磁，这种励磁方法相当于多值方波励磁，有利于消除或减少方波法励磁所带来的微分干扰。 紧接着，在微流量电磁流量计转换器部分，通过有效地设计电路消除或极大地减小了同相干扰、正交干扰和50Hz工频干扰等干扰信号，将流量信号恢复并放大到0～2.5V之间。 最后，流量电压信号经过A／D采样后输入到微处理器中。经过微处理器处理后完成各种显示、控制及通信等功能，实现流量计的高度智能化。 第二部分：LS旋转流量计超低功耗设计的研究 此部分就流量计发展的第二个方向来设计出功耗超低、体积小巧、性能较高 的LS旋转式流量计。 功耗问题一直困扰着流量计的单表设计。以前的单表型流量计都无法降低功 耗到足以用干电池供电，最多只是采用蓄电池供电。本课题设计出的LS旋转流 量计真正实现了超低功耗，可以采用干电池长期供电。 文中紧紧抓住功耗问题，分别从传感器等输入通道、单片机的选择及运行方 式、液晶显示等传感器输出通道及电池电源的选择等方面对LS旋转流量计进行 超低功耗分析、设计。最终设计出的整套系统达到了真正的超低功耗。本部分研 究的流量计对流体介质没有特别的要求，因此应用范围广。更为重要的是流量计 系统功耗极低，特别适合于在市用电无法供电的情况下对流量进行测量。 课题研究中所提及的各种超低功耗设计原则和思想可以应用到其他的电路 设计中去。 本文的创新之处在于采用矩形测量导管大大增加微流量条件下的感应电动 势；采用输出频率可调的正弦波电流作为励磁电流达到消除50HZ频干扰和减 少正交干扰的目的；利用单片机等高端现代电子产品实现了电磁流量计的高度智 能化及设计出真正的超低功耗的、可用干电池长期供电的LS旋转流量计。更多还原

【Abstract】 There are two development directions of flowmeter: one is flowmeters with little volume, little weight, low price and convenient to setup and use. Another is flowmeters with high precision and performance.This paper consists of two parts.Part one: Research on the measurement of low-velocity flow with intelligence electromagnetic flowmeter.At first, the paper analyses the difficulty when measuring the low-velocity flow with common electromagnetic flowmeter. According to result, we use the rectangle-shape pipeline instead of circuit-shape pipeline used commonly to measure the flow. Then we set up the model of rectangle-shape pipeline. We compare it to circuit-shape pipeline on sides of the value of induced electromotive force, pressure loss when liquid flow trough the pipeline and resistance’s value of the sensor. We get the result that we can finish the measurement of low-velocity flow by using the rectangle-shape pipeline. This is the theory using to measure the flux of low-velocity flow.Secondly, the paper analyses the virtues and shortcomings of inducing-magnetic mode that use alternating current at 50Hz or rectangle-wave current. Then the paper suggests that the flowmeter should use alternating current to induce the magnetic whose frequency is adjustable. Comparing to inducing-magnetic mode with 50Hz alternating current, we can use lower frequency alternating current to induce the magnetic so that it can eliminate the noise at 50Hz frequency and weaken the noise whose phase lags signal 90?greatly. Comparing to inducing-magnetic mode using rectangle-wave current as the signal, using low frequency to induce magnetic can eliminate (weaken) the differential coefficient noise.Thirdly, it eliminates or weakens all different noise by designing the circuitry effectively in the transforming signal part.At last, the flux signal is inputted to the microprocessor after A/D sampling. Then it finishes all kinds of controlling, displaying and communication function. So, the flowmeter is intelligent.Part two: The research on utra-low power consumption design of LS flowmeter.This part finishes design of LS flowmeter with utra-low power consumption, little volume and high performance according to the second direction of flowmeter development.The problem of consumption puzzles people on the design of single function flowmeter. The flowmeter designed in the past couldn’t decrease the consumption so low that the whole system can be supplied by dry battery. The best one is supplied by accumulator. The flowmeter designed in this paper is true utra-low power consumption, and it can be supplied by dry battery.The paper finishes the analyze and design on utra-low power consumption from sides of the design of sensor, the choice and running of microprocessor display with LCD. At last, the paper finishes the flowmeter with utra-low power consumption. This flowmeter hasn’t extra demand, so its apply area is very wide. And it is specially applied to area where there isn’t industrial electrical source for its utra-low power consumption.The principle used in this paper can be used to other circuit design. The innovation in this paper is list below(1) Use rectangle-shape pipeline so that the inducing electromotive force could be enhanced;(2) Use alternating current whose frequency is adjustable to induce the magnetic;(3) Make the flowmeter intelligent by use the microprocessor;(4) Finish designing the LS flowmeter with utra-low power consumption.更多还原