论文总字数：40484字

目录

1.引言 1

1.1 设计背景及相关技术介绍 1

1.1.1 密度法 1

1.1.2射线法 1

1.1.3 短波法 2

1.1.4 射频法 3

1.1.5电容法 4

1.2设计概述 4

2.硬件系统设计 1

2.1检测电容探头设计及制造方法 1

2.1.1检测电容探头结构 1

2.1.2检测电容探头原理 3

2.1.3检测电容探头仿真测试 6

2.1.4检测电容探头PCB制作及参数测量 8

2.1.5检测电容探头小结 12

2.2测量系统设计 12

2.2.1总体硬件设计 12

2.2.2主控系统 13

2.2.3探头电容检测电路 16

2.2.4外置存储 17

2.2.5用户交互 19

2.2.6外部通信 22

2.2.7电源系统 23

3.软件系统设计 25

3.1嵌入式软件系统 25

3.1.1 uCOSIII嵌入式操作系统 25

3.1.2水含量测量系统 25

3.2外设模块驱动层 26

3.2.1探头电容检测电路驱动 26

3.2.2存储驱动 28

3.2.3用户交互设备驱动 28

3.2.4外部通信驱动 28

3.3系统运行服务层 28

3.3.1内存管理系统 28

3.3.2 FATs文件系统 29

3.3.3 EMWIN图形系统 30

3.4系统应用层 30

4.系统测试及分析 32

4.1系统外设测试 32

4.1.1外部SRAM和SD卡数据读写测试 32

4.1.2测量芯片读写测试 33

4.2系统油中水含量数据测量及分析 34

5. 小结及创新性 42

参考文献 44

本科期间科研成果 46

致谢 48

基于电场边缘效应和PCB技术的油中水含量测量系统设计

阮玮琪

, China

Abstract: Given the shortcomings of current market-applied methods and instruments in oil-water measurement, a measurement system based on capacitive fringing field effect and PCB technology was designed, consisting of self-designed detection probe, capacitance detection circuit, embedded processor, external SRAM, SD card memory, RS485 communication module, LCD touch screen, keyboard, power supply module and other components. Different oil water content affects the dielectric constant. And the design of oil-water capacitance detection probe was optimized by finite element analysis software COMSOL and capacitive fringing field effect of the capacitor plate amp; PCB technology. Capacitance detection circuit was designed in using the up to 28-bit accuracy capacitance detection chip FDC2212 and the side stick SMA shielding head, which could improve the anti-jamming performance of the circuit. The system control hardware utilized embedded processor STM32F407ZGT6 based on ARM-M4 kernel and ran uCOSIII real-time embedded multi-tasking operating system. External SRAM and SD card memory provided the system operation and storage space. RS485 communication module could be extended to other handheld communication devices. LCD touch screen and keyboard for users provided good interaction experience. Experimental data showed that the oil-water measurement system was a successful implementation of the prototype, which detection error was less than 1% and sensitivity could be achieved in 3.3PF/%, given the oil-water ranged from 0 to 80%. The follow-up performance of the detection system could be improved through calibration and data compensation.

Key words: capacitive detecting probe, capacitive fringing filed effect, PCB technology, embedded operating system

引言

1.1 设计背景及相关技术介绍

水分测量仪是一种常用检测仪器，有着广泛的工业、农业、日常生活应用。工业上汽油的品质跟水含量有很大的关系，水含量过高会导致汽油燃爆不充分，损坏发动机气缸；农业上粮食的储藏需要将仓库空气中的水含量控制在一个合适范围内以防止粮食因水分过多而发生呼吸作用导致发热霉变，因此需实时检测仓库中粮食的水含量；而食用油的大型罐体储藏对于水含量的要求更加苛刻，水分过高会直接导致油的腐坏发霉，失去食用价值；此外，茶叶的含水量直接影响着茶叶的品质和售价，过多的水分就会让茶叶保存困难易失去功效。

对于水含量的测量，目前常见的有密度法、射线法、短波法、射频法和电容法，不同方法测量范围和原理不一样，对应的优缺点也很明显。