WO2017031833A1 - 一种基于电桥法测量生物体介电常数装置 - Google Patents

一种基于电桥法测量生物体介电常数装置 Download PDF

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WO2017031833A1
WO2017031833A1 PCT/CN2015/094080 CN2015094080W WO2017031833A1 WO 2017031833 A1 WO2017031833 A1 WO 2017031833A1 CN 2015094080 W CN2015094080 W CN 2015094080W WO 2017031833 A1 WO2017031833 A1 WO 2017031833A1
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circuit
gpio
tim
dielectric constant
tim2
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PCT/CN2015/094080
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French (fr)
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南群
王锐锐
岳瑞娟
聂晓慧
田甄
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北京工业大学
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables

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  • the present invention relates to a device for measuring dielectric constant, in particular for measuring the measurement of the dielectric constant of an ex vivo organism.
  • the dielectric constant of an organism is an important physical quantity, which reflects the polarization characteristics and loss phenomena of biological tissues under the action of an external electric field. It is determined by the intrinsic properties of the substance itself. Different materials in the same organism have different water content in the same tissue and different composition of each tissue, etc., which will result in different values of dielectric constant.
  • the dielectric constant of living tissue is an important physical quantity, which is to study the electromagnetic properties and the interaction between electromagnetic waves and living tissue.
  • Pathological changes in biological tissues such as inflammation, edema, congestion, or cancer, can be reflected in the dielectric properties of biological tissues, that is, the dielectric constant of related tissues changes, such as according to the tissue in which the lesion occurs and the normal tissue.
  • the difference in constants allows the location and size of the tumor to be detected. Therefore, measuring the dielectric constant of biological tissues has practical value and practical significance.
  • the methods for measuring the dielectric constant are a bridge method, a resonant cavity method, a free space method, a coaxial probe method, a transmission method, and the like.
  • the method of measuring the complex permittivity can reach a frequency range of 1-10 17 Hz, and the temperature can range from -273.15 ° C to 1650 ° C.
  • the data reported by different researchers often differs. Especially for materials with very low losses and extremely high losses, the data error is greater.
  • the Chinese invention patent publication date is April 23, 2014, and the publication number CN201210255630 discloses a method for measuring brain edema change based on the minimum impedance frequency.
  • the invention uses a impedance measurement to calculate the load impedance, and obtains a method for measuring the change of the dielectric constant of the brain tissue.
  • the method based on the bridge method measured by the present invention is two principles, and each method has advantages and disadvantages.
  • the device made by the invention has the advantages of convenient carrying, fast measuring speed and accurate data, and can be used for real-time monitoring devices.
  • the present invention provides a device for measuring a dielectric constant constant based on a bridge method, which can measure not only the capacitance and dielectric constant of a non-living body but also the dielectric constant of an ex vivo organism.
  • the technical solution adopted by the present invention is a device for measuring a biological dielectric constant based on a bridge method, the device comprising a power supply circuit, a sensor circuit, a signal acquisition circuit, a signal processing module, and a data display module; Different circuits provide the required voltage; the sensor circuit is used to convert the capacitance value Cx into a square wave oscillation signal which is inversely proportional thereto; the signal acquisition circuit is used for collecting and preliminary processing the square wave oscillation signal generated by the sensor circuit; the signal processing module And the data display module is configured to perform final processing on the signal collected by the acquisition signal circuit.
  • the power supply circuit provides corresponding voltages for the sensor circuit, the signal acquisition circuit, the signal processing module, and the data display module, so that the circuits and modules can work normally.
  • the sensor circuit transmits the square wave signal collected by the sensor to the signal acquisition circuit, passes through the filtering of the signal acquisition circuit, and then sends it to the signal processing module, and passes the signal.
  • the program processing of the preset software in the processing module is finally sent to the display module for display, showing the values of capacitance and dielectric constant.
  • the signal acquisition module is connected with the signal processing module, and the signal acquisition module receives and buffers the signal input by the sensor circuit and outputs the signal to the signal processing module to prevent excessive interference voltage or current from being excessively disturbed and damaged to the downstream single-chip circuit. .
  • the signal processing module adopts a single chip microcomputer as a main control chip, and the peripheral circuit thereof comprises a reset circuit, a crystal oscillator circuit and a surge protection circuit.
  • the reset circuit uses the delay characteristic of the RC circuit.
  • a 10K resistor and a 10nF capacitor are selected, and the time delay is in accordance with the reset requirement of the system chip.
  • the resistor, capacitor, and switch are connected in parallel to port 3 of the main control chip. And the resistor is connected in series with a 3.3V power supply.
  • the crystal oscillator circuit uses an 8M passive crystal oscillator.
  • the 8M passive crystal oscillator is grounded through a 20pF capacitor at both ends.
  • the circuit is simple and it is easy to start the crystal oscillator.
  • the surge protection circuit is two parallel capacitors C 1 and C 2 used to prevent the instantaneous high voltage from damaging the chip.
  • the surge protection circuit is connected to the crystal oscillator circuit and then connected to the MCU port 2.
  • the power supply circuit uses the main control chip and the circuit to reduce the charging voltage from 5V to 4.2V to charge the lithium battery to supply power to the sensor circuit.
  • the signal processing module and the display module with the MCU as the core require a 3.3V power supply voltage. Since the output voltage of the lithium battery is higher than 3.3V, the voltage conversion chip is required to convert the voltage into 3.3V to supply power to the signal processing module and the display module.
  • a parallel plate capacitor is disposed in the sensor circuit, and the living body to be tested is placed in the middle of two parallel plates of the parallel plate capacitor.
  • the two parallel plate structures of the parallel plate capacitor are circular or square, and the outer surfaces of the two parallel plates of the parallel plate capacitor are coated.
  • the two parallel plate materials of the parallel plate capacitor are aluminum or copper. And according to the literature, the edge effect is negligible when the ratio of the width H to the spacing d of the parallel plate capacitor is greater than a certain value. Therefore, the diameter of the circular parallel plate is set to 9 cm - 11 cm, and the side length of the square parallel plate is 8 cm - 10 cm, that is, the maximum spacing of the two parallel plates needs to be less than 5 mm - 6 mm, and should be minimized when measuring the dielectric constant. The spacing between the plates.
  • the sensor circuit comprises a capacitor, a multi-resonant circuit; the multi-resonant circuit comprises an LMC555 counter, a resistor R1, and a resistor R2.
  • the capacitor is connected to the 5 port of the LMC555 counter, and the resistor R1 and the resistor R2 are respectively connected to the port 5 and the port 2.
  • R1 and R2 square wave signals of different frequencies are obtained.
  • Port 3 is located at the output square wave signal end.
  • the single chip adopts STM32F051 as the main control chip.
  • the EDA development language and software platform of the single-chip microcomputer is the MDK developed by ARM. It integrates the advantages of Keil's ⁇ Vision IDE environment and ARM compiler tool RVCT. It is also called Keil ⁇ Vision 4.
  • the integrated environment can complete the code well. Editing, compiling, linking, debugging, and online simulation debugging. Software compiled on this platform is very convenient to write the calculation formulas that need to be calculated.
  • the algorithm of single-chip signal processing is: When the system clock reaches 1ms (set unit time), the STM32 chip has captured N cycles (the number of periodic changes), the frequency f, the capacitance value can be obtained, and finally the creature is obtained.
  • the relative dielectric constant of the body GPIO initialization, time base initialization, signal acquisition procedures, signal processing procedures are as follows:
  • GPIO_InitStructure.GPIO_Pin GPIO_Pin_0;//Select the GPIO pin A0 to be controlled
  • GPIO_InitStructure.GPIO_Mode GPIO_Mode_AF;//Set the pin mode to multiplexed output
  • GPIO_InitStructure.GPIO_Speed GPIO_Speed_50MHz; / / pin rate is 50MHz
  • GPIO_InitStructure.GPIO_OType GPIO_OType_PP;
  • GPIO_InitStructure.GPIO_PuPd GPIO_PuPd_NOPULL;
  • TIM_Period 0xFFFFFF;//When the timer counts from 0 to 4294967295, it is 4294967296 times, which is a timing period.
  • TIM_Prescaler 0;//Set prescaler: no prescaler, ie 48MHz
  • TIM_ClockDivision 0;//Set the clock division factor: no division
  • TIM_CounterMode TIM_CounterMode_Up;//Up counting mode
  • TIM_TimeBaseInit (TIM2,&TIM_TimeBaseStructure);//Initialize TIM2 according to the above control parameters
  • TIM_ETRConfig (TIM2, TIM_ExtTRGPSC_OFF, TIM_ExtTRGPolarity_Inverted, 0); //TIM2 clock source selects external trigger input capture; no prescaler, ie captures every rising edge
  • Temp TIM_GetCounter(TIM2);//frequency f
  • TIM_SetCounter (TIM2,0);//Set the TIM2 value to 0.
  • the invention has the beneficial effects that the invention is based on the single chip STM32F051, and the sensor circuit succeeds in converting the object to be tested into a capacitor first, and then into a square wave signal, which is collected by the peripheral circuit of the single chip microcomputer and input into the single chip microcomputer. Processing, then the microcontroller transmits the processing result to the display module.
  • the device has the advantages of simple principle, small module, convenient carrying, fast measuring speed and high sensitivity. It can provide some convenience for real-time monitoring of parameters related to dielectric constant.
  • Figure 1 is a schematic structural view of the device.
  • Fig. 2 is a graph showing the trend of the dielectric constant of pig liver 1 as a function of moisture.
  • Figure 3 is a graph showing the trend of the dielectric constant of pig liver 2 as a function of moisture.
  • a device for measuring a dielectric constant of a living body based on a bridge method is characterized in that it includes a power supply circuit that supplies a required voltage for different circuits, and converts the capacitance value Cx into a square wave inversely proportional thereto.
  • different voltage supply modules will reduce the charging voltage from 5V to 4.2V to charge the lithium battery to supply power to the sensor circuit.
  • the voltage conversion chip converts the voltage into 3.3V, which is a signal.
  • the processing module and the display module are powered.
  • the parallel circuit capacitor in the sensor circuit and the circuit constitutes a measuring device. After the object to be tested is placed in the parallel plate, a variable capacitor Cx is connected, and the capacitor is connected to a multi-resonant circuit composed of LMC555, R1, R2, and the like.
  • the sensor circuit that constitutes the system is capable of converting the capacitance value Cx into a square wave oscillation signal that is inversely proportional thereto. When the measured medium fills the parallel plate capacitor, it causes a periodic change of the multivibrator, causing a change in the relative dielectric constant.
  • the signal acquisition module is connected to the signal processing module, and the signal sent by the sensor can be received and buffered and sent to the signal processing module.
  • the information processing module with the single chip as the core then processes the information transmitted from the acquisition module and sends it to the display module for display.
  • the dielectric constant measuring device is tested: a power supply, a parallel plate capacitor, three 103 capacitors, and a system circuit designed by the present invention.
  • the relative error of the 103 capacitor is about 7% to 8%, which is in line with the error of the capacitor itself, indicating that this scheme is feasible and high.
  • the relative dielectric constant of A4 paper and wood board is very close to the reference value in the literature (paper reference value 3.24, wood board reference value 4.86), which further verifies the reliability of this scheme.
  • paper reference value 3.24, wood board reference value 4.86 the reference value in the literature
  • it still differs from the values in the literature, which are attributed to the following two reasons: one is due to the error caused by the imperfection of the circuit and the self-made parallel plate capacitor, and the other side is because the literature does not indicate What is the paper, wood, even the same paper, may be produced by different manufacturers, resulting in different material structure of the paper, so that the dielectric constant is different. Even the same kind of wood board will cause different dielectric constants due to different individuals. Overall, this measurement is reliable.
  • the living tissue has the characteristics of high dielectric constant, irregular shape and high water content.
  • the living tissue measured by the patent of the present invention is pig liver, and the value of the dielectric constant is affected by factors such as the shape, size and internal structure of the biological sample. So even if it comes from the same pig liver, but because the internal structure of pig liver is not uniform and does not, Therefore, the measured relative dielectric constants cannot be simply averaged and must be listed one by one.
  • the study of the present invention is a trend of the dielectric constant of pig liver as a function of water content.
  • the dielectric constants of the same tissue in the same organism are also very different. Because the water content and pores of different parts of the same tissue are different, the dielectric constant results are different. At the same time, it is not difficult to see that the relative dielectric constant of the same organism decreases with the decrease of water content, especially after 15 minutes, the dielectric constant decreases the steepest, not only because the rate of loss of liver surface moisture is fast, but also Because of the death of pig liver surface cells, when the electric field is placed again, the polar molecules of the surface cells are no longer active, causing the dielectric constant to decrease. From the trend and results of the dielectric constant of the two tissues, the measurement of the dielectric constant of the device is reliable.

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Abstract

一种基于电桥法测量生物体介电常数装置，该装置包括供电电路、传感器电路、信号采集电路、信号处理模块、显示模块；供电电路为不同电路提供所需电压；传感器电路用以将电容值转变为与之成反比的方波振荡信号；信号采集电路用以将传感器电路产生的方波振荡信号进行采集并初步处理；信号处理模块和显示模块用以将信号采集电路采集到的信号进行最终处理。在传感器电路成功将待测物体在先变为电容，再变为方波信号后被单片机的外围电路采集并输入单片机进行处理，随后单片机将处理结果传输给显示模块。该装置可以实时监测待测物体的介电常数。

Description

一种基于电桥法测量生物体介电常数装置 技术领域
本发明涉及一种介电常数测量的装置，尤其测量离体生物体介电常数的测量。
背景技术
生物体的介电常数是一个重要的物理量，它反映了生物体组织在外电场作用下的极化特性和损耗现象的发生，它是由物质本身的内在属性所决定。同一生物体的不同组织同一组织的含水量不同以及各组织的组成成分不同等等，都会导致介电常数的取值不同。
生物体组织的介电常数是一个重要的物理量，它是研究电磁特性及电磁波与生物体组织之间的相互作用。生物组织发生的病变，如发炎、水肿、充血或癌变等，都能在生物组织的介电特性上反映，即相关组织的介电常数会发生变化，比如根据发生病变的组织与正常组织介电常数的不同，可以检测到肿瘤的位置以及大小。因此测量生物组织的介电常数具有实用价值和现实意义。
测量介电常数的方法很多，根据测量频段的不同，使用的方法也有所区别。目前测量介电常数采用的方法是有电桥法、谐振腔法、自由空间法、同轴探针法、传输法等。一般测量复介电常数的方法可达到频率范围是1-1017Hz，温度的范围可从-273.15℃到1650℃。但即使是上述的范围，仍然存在测量的准确度的问题。因为对于同一种材料(非生物体组织和生物体组织)，不同的科研工作者报道的数据往往有出入。尤其是对于极低的损耗和极高的损耗的材料，数 据误差更大。而且目前用于测量生物体介电常数的方法也较少。中国发明专利专利公开日为2014年04月23日，公开号CN201210255630公开了一种基于最小阻抗频率的脑部水肿变化测量方法。该发明采用通过阻抗测量来计算负载阻抗，得到一种测量大脑组织介电常数变化的方法，与本发明所采用基于电桥法测量的方法是两种原理，方法各有利弊。而且本发明制作的装置携带方便，测量速度快，数据也比较准确，可以进行实时监测装置使用。
发明内容
本发明提供了一种基于电桥法测量生物体介电常数装置，该装置不仅可以测量非生物体的电容和介电常数，还可以测量离体的生物体的介电常数。
为实现以上功能，本发明采用的技术方案为一种基于电桥法测量生物体介电常数装置，该装置包括供电电路、传感器电路、信号采集电路、信号处理模块、数据显示模块；供电电路为不同电路提供所需电压；传感器电路用以将电容值Cx转变为与之成反比的方波振荡信号；信号采集电路用以将传感器电路产生的方波振荡信号进行采集并初步处理；信号处理模块和数据显示模块用以将采集信号电路采集到的信号进行最终处理。
如图1所示，供电电路为传感器电路、信号采集电路、信号处理模块和数据显示模块提供相应电压，使得各电路及模块能够正常工作。传感器电路将传感器采集到的方波信号传给信号采集电路，经过信号采集电路的滤波等工作，再送入到信号处理模块，经过信 号处理模块中的预置软件的程序处理，最后送到显示模块进行显示，显示出电容和介电常数等值。
所述信号采集模块与信号处理模块连接，信号采集模块将传感器电路输入的信号接收并缓冲后输出至信号处理模块，以防止过大的干扰电压或电流过大对下游的单片机电路造成干扰和损坏。
所述信号处理模块采用单片机为主控芯片，其外围电路包括复位电路、晶振电路和浪涌保护电路。复位电路是利用RC电路的延时特性，此处选用一个10K电阻和10nF电容，时间延时符合系统芯片的复位要求。电阻、电容、开关并联后接于主控芯片的端口3。并且电阻上串联3.3V电源。晶振电路选用的是8M无源晶振，8M无源晶振两端分别通过20pF的电容接地，电路简单且很容易使晶振起振。浪涌保护电路是防止瞬间高电压损坏芯片而采用的两个并联电容C1、C2，浪涌保护电路与晶振电路连接后接于单片机端口2。
所述供电电路利用主控芯片和电路将充电电压从5V的电压降到4.2V给锂电池充电为传感器电路供电。
在单片机为核心的信号处理模块和显示模块需3.3V电源电压，由于锂电池的输出电压高于3.3V，所以需要电压转换芯片将电压转换成3.3V，为信号处理模块和显示模块供电。
所述传感器电路中设有一平行板电容器，该平行板电容器的两平行板中间放置待测生物体。
所述平行板电容器的两平行板结构为圆形或方形，平行板电容器的两平行板的外表面覆膜。
所述平行板电容器的两平行板材料为铝或铜。并且据查阅文献，平行板电容的的宽度H和间距d之比大于一定的值时边缘效应即可以忽略不计。因此圆形平行板的直径设置为9cm—11cm，而方形平行板的边长为8cm—10cm，即其两平行板板最大间距需要小于5mm—6mm，并且在测量介电常数时要尽量减小极板间的间距。
所述传感器电路包括电容器，多谐振荡电路；多谐振荡电路包括LMC555计数器、电阻R1、电阻R2。其中电容器连接于LMC555计数器的5端口，电阻R1、电阻R2分别连接于端口5和端口2。变换R1和R2的阻值，便获得不同频率的方波信号。端口3位于输出方波信号端。
所述单片机采用STM32F051为主控芯片。
单片机的EDA开发语言及软件平台是ARM公司开发的工具MDK，集Keil的μVision IDE环境与ARM编译工具RVCT两者的优势于一体，又称之为KeilμVision 4，该集成环境能够很好地完成代码的编辑、编译、链接、调试以及在线仿真调试。在这个平台上编译的软件写入所需要计算的计算公式十分方便。
单片机信号处理的算法是：当达到系统时钟的1ms(设定的单位时间)，STM32芯片已经捕获了N个周期(周期性变化的次数)，频率f、电容值即可求出，最终得到生物体的相对介电常数。GPIO初始化、时基初始化、信号采集程序、信号处理程序如下：
GPIO初始化
GPIO_InitTypeDefGPIO_InitStructure；//初始化GPIO结构体
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure；
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA,ENABLE)；//使能GPIOA
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE)；//使能TIM2
GPIO_InitStructure.GPIO_Pin＝GPIO_Pin_0；//选择要控制的GPIO引脚A0
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA,ENABLE)；
GPIO_InitStructure.GPIO_Mode＝GPIO_Mode_AF；//设置引脚的模式为复用输出
GPIO_InitStructure.GPIO_Speed＝GPIO_Speed_50MHz；//引脚的速率为50MHz
GPIO_InitStructure.GPIO_OType＝GPIO_OType_PP；
GPIO_InitStructure.GPIO_PuPd＝GPIO_PuPd_NOPULL；
GPIO_Init(GPIOA,&GPIO_InitStructure)；//按照上述控制参数初始化GPIO
时基初始化
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure；
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE)；
TIM_TimeBaseStructure.TIM_Period＝0xFFFFFFFF；//当定时器从0计数到4294967295，即为4294967296次，为一个定时周期
TIM_TimeBaseStructure.TIM_Prescaler＝0；//设置预分频：不预分频，即为48MHz
TIM_TimeBaseStructure.TIM_ClockDivision＝0；//设置时钟分频系数：不分频
TIM_TimeBaseStructure.TIM_CounterMode＝TIM_CounterMode_Up；//向上计数模式
TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure)；//按照上述控制参数初始化TIM2
信号采集程序
/*配置TIM2为外部触发输入捕获*/
TIM_ETRConfig(TIM2,TIM_ExtTRGPSC_OFF,TIM_ExtTRGPolarity_Inverted,0)；//TIM2的时钟源选择外部触发输入捕获；无预分频器，即捕获每一个上升沿
TIM_SetCounter(TIM2,0)；
TIM_Cmd(TIM2,ENABLE)；//使能TIM2
信号处理程序
if(Main_Thread＝＝1)
{
temp＝TIM_GetCounter(TIM2)；//频率f
temp2＝1000000000000/(temp*0.693*32400*3)；//电容值
sprintf(b,"Pmt:％.3f",temp2*0.005/(0.082*0.082*8.85))；//相对介电常数
Main_Thread＝0；
TIM_SetCounter(TIM2,0)；//设置TIM2数值为0
本发明专利的有益效果在于：本发明是以单片机STM32F051为主控芯片，在传感器电路成功将待测物体在先变为电容，再变为方波信号后被单片机的外围电路采集并输入单片机进行处理，随后单片机将处理结果传输给显示模块。此装置原理简单，模块比较小、方便携带、测量速度快，灵敏度高等特点。可以为实时监测与介电常数相关的参数提供一定的便利。
附图说明
图1为本装置的结构示意图。
图2是猪肝1的介电常数随水分变化趋势图。
图3是猪肝2的介电常数随水分变化趋势图。
具体实施方式
下面将结合附图和实施例，详细说明本发明专利的技术方案。
附图1是本发明专利的系统结构示意图。由图1可知，一种基于电桥法测量生物体介电常数的装置，其特征在于：包括为不同电路提供所需要电压的供电电路、将将电容值Cx转变为与之成反比的方波振荡信传感器电路，将传感器电路产生的方波信号采集并初步处理的信号采集电路，将采集信号电路采集来的信号进行最终处理的信号处理模块和数据显示模块。
首先将不同电压供电模块将充电电压从5V的电压降到4.2V给锂电池充电,为传感器电路供电。而在传感器芯片和显示模块需要3.3V的电源电压上，故由电压转换芯片将电压转换成3.3V，为信号 处理模块和显示模块供电。
传感器电路与电路中的平行板电容器构成一个测量装置，这个平行板中放置待测物体的后就是可变的电容器Cx，将该电容器接入由LMC555、R1、R2等构成的多谐振荡电路中就组成了该系统的传感器电路,该电路能将电容值Cx转变为与之成反比的方波振荡信号。当被测介质填充平行板电容器时，会引起多谐振荡器的周期变化，从而引起相对介电常数发生变化。
信号采集模块是连接在信号处理模块上的，可以将传感器送来的信号接收并缓冲后送入信号处理模块。
以单片机为核心的信息处理模块再将采集模块传来的信息利用事先编制好的软件进行处理并送入到显示模块进行显示。
实施例1
先进行介电常数测量装置的检验：准备电源、平行板电容器、3个103电容、本发明专利所设计的系统电路。
将电容接入传感器电路，然后启动电源，初始化后再启动传感器电路，在显示屏中读出数据。结果如下
Figure PCTCN2015094080-appb-000001
从上表可知，103电容的相对误差为7％～8％左右，符合其电容本身误差，说明此方案可行且精较高。
实施例2
准备如下材料：电源、自制的方形平行板电容器(边长H＝8.2cm)、A4纸、木板、猪肝若干个(新鲜)、本发明专利设计的系统电路。与实例1相同先连接和启动电路，具体如下：把加工好的A4纸平坦地放入平行板电容器中，接入设计的电路中之后打开电源，显示屏即可显示出A4纸的相对介电常数，清理A4纸后放入木板，即可得到木板的相对介电常数。
Figure PCTCN2015094080-appb-000002
由上表可以看出，A4纸和木板的相对介电常数与文献中的参考值(纸的参考值3.24，木板的参考值4.86)很接近，更加验证此方案的可靠性。虽然与参考值很接近，但是仍然与文献中的值有出入，归结于以下两方面原因：一方面是由于电路以及自制的平行板电容器不完善导致的误差，另一面是因为文献中的没有标明是什么的纸张、木板，即使是同样的纸张，也有可能因为不同厂家生产的，导致纸张的材料结构有所不同，从而使介电常数有所区别。即使是同一种类的木板，也会因为不同个体的原因导致介电常数不同等等。总的来说，这个测量结果是可靠的。
实施例3
生物体组织具有介电常数高、形状不规则，含水量高的特点。本发明专利测量的生物体组织是猪肝，由于生物体样品的形状、尺寸及内部结构不均匀等因素，都会影响介电常数的取值。所以即使来自于同一个猪肝，但是由于猪肝的内部结构并非均匀且有所不， 因此不能把测得的相对介电常数进行简单的平均，需一一列出。本发明研究是猪肝的介电常数随含水量的变化趋势。
从新鲜的同一块猪肝同时切两个测试样品，标记为猪肝1和猪肝2测量完毕之后把其放入楼上的阴凉处(实验室在地下室)，这样可以使其水分蒸发快一点。用手术刀把猪肝加工之后放入平行板电容器中，可以直接在OLED显示屏上读出数值相对介电常数，结果的趋势图如图2和图3所示。
由上图可以看出，对于同一生物体同一组织的不同部位，其介电常数也是有很大区别的。因为同一组织中的不同部位其含水量和孔隙等有差别，所以导致介电常数结果有差别。同时也不难看出，同一生物体的相对介电常数随着水分的减少而下降，尤其是15分钟之后，介电常数下降的趋势最陡，这不仅是因为肝脏表面水分失去的速率快，还因为猪肝表面细胞死亡的原因，当再次放入电场时，表面细胞的极性分子不再活跃，使得介电常数下降。从两块组织的介电常数变化趋势和结果上可知，此装置介电常数的测量结果是可靠的。
Figure PCTCN2015094080-appb-000003
Figure PCTCN2015094080-appb-000004
以上所述仅为本发明的优选实施例，并不用于限制本发明。

Claims (6)

  1. 一种基于电桥法测量生物体介电常数装置，其特征在于：该装置包括供电电路、传感器电路、信号采集电路、信号处理模块、数据显示模块；供电电路为不同电路提供所需电压；传感器电路用以将电容值转变为与之成反比的方波振荡信号；信号采集电路用以将传感器电路产生的方波振荡信号进行采集并初步处理；信号处理模块和数据显示模块用以将采集信号电路采集到的信号进行最终处理；
    供电电路为传感器电路、信号采集电路、信号处理模块和数据显示模块提供相应电压，使得各电路及模块能够正常工作；传感器电路将传感器采集到的方波信号传给信号采集电路，经过信号采集电路的滤波等工作，再送入到信号处理模块，经过信号处理模块中的预置软件的程序处理，最后送到显示模块进行显示，显示出电容和介电常数等值；
    所述信号采集模块与信号处理模块连接，信号采集模块将传感器电路输入的信号接收并缓冲后输出至信号处理模块，以防止过大的干扰电压或电流过大对下游的单片机电路造成干扰和损坏；
    所述信号处理模块采用单片机为主控芯片，其外围电路包括复位电路、晶振电路和浪涌保护电路；复位电路是利用RC电路的延时特性，此处选用一个10K电阻和10nF电容，时间延时符合系统芯片的复位要求；电阻、电容、开关并联后接于主控芯片的端口3；并且电阻上串联3.3V电源；晶振电路选用的是8M无源晶振，8M无源晶振两端分别通过20pF的电容接地，电路简单且很容易使晶振 起振；浪涌保护电路是防止瞬间高电压损坏芯片而采用的两个并联电容C1、电容C2，浪涌保护电路与晶振电路连接后接于单片机端口2；
    所述供电电路利用主控芯片和电路将充电电压从5V的电压降到4.2V给锂电池充电为传感器电路供电；
    在单片机为核心的信号处理模块和显示模块需3.3V电源电压，由于锂电池的输出电压高于3.3V，所以需要电压转换芯片将电压转换成3.3V，为信号处理模块和显示模块供电；
    所述传感器电路中设有一平行板电容器，该平行板电容器的两平行板中间放置待测生物体。
  2. 根据权利要求1所述的一种基于电桥法测量生物体介电常数装置，其特征在于：所述平行板电容器的两平行板结构为圆形或方形，平行板电容器的两平行板的外表面覆膜。
  3. 根据权利要求1所述的一种基于电桥法测量生物体介电常数装置，其特征在于：所述平行板电容器的两平行板材料为铝或铜；圆形平行板的直径设置为9cm—11cm，而方形平行板的边长为8cm—10cm，两平行板最大间距需要小于5mm—6mm，并且在测量介电常数时要尽量减小极板间的间距。
  4. 根据权利要求1所述的一种基于电桥法测量生物体介电常数装置，其特征在于：所述传感器电路包括电容器，多谐振荡电路；多谐振荡电路包括LMC555计数器、电阻R1、电阻R2；其中电容器连接于LMC555计数器的5端口，电阻R1、电阻R2分别连接于 端口5和端口2；变换R1和R2的阻值，便获得不同频率的方波信号；端口3位于输出方波信号端。
  5. 根据权利要求1所述的一种基于电桥法测量生物体介电常数装置，其特征在于：所述单片机采用STM32F051为主控芯片。
  6. 根据权利要求1所述的一种基于电桥法测量生物体介电常数装置，其特征在于：
    单片机信号处理的算法是，当达到系统时钟的1ms，STM32芯片已经捕获了N个周期，频率f、电容值即可求出，最终得到生物体的相对介电常数；GPIO初始化、时基初始化、信号采集程序、信号处理程序如下，
    GPIO初始化
    GPIO_InitTypeDefGPIO_InitStructure；//初始化GPIO结构体
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure；
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA,ENABLE)；//使能GPIOA
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE)；//使能TIM2
    GPIO_InitStructure.GPIO_Pin＝GPIO_Pin_0；//选择要控制的GPIO引脚A0
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA,ENABLE)；
    GPIO_InitStructure.GPIO_Mode＝GPIO_Mode_AF；//设置引脚的模式为复用输出
    GPIO_InitStructure.GPIO_Speed＝GPIO_Speed_50MHz；//引脚的速率为50MHz
    GPIO_InitStructure.GPIO_OType＝GPIO_OType_PP；
    GPIO_InitStructure.GPIO_PuPd＝GPIO_PuPd_NOPULL；
    GPIO_Init(GPIOA,&GPIO_InitStructure)；//按照上述控制参数初始化GPIO
    时基初始化
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure；
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE)；
    TIM_TimeBaseStructure.TIM_Period＝0xFFFFFFFF；//当定时器从0计数到4294967295，即为
    4294967296次，为一个定时周期
    TIM_TimeBaseStructure.TIM_Prescaler＝0；//设置预分频：不预分频，即为48MHz
    TIM_TimeBaseStructure.TIM_ClockDivision＝0；//设置时钟分频系数：不分频
    TIM_TimeBaseStructure.TIM_CounterMode＝TIM_CounterMode_Up；//向上计数模式
    TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure)；//按照上述控制参数初始化TIM2
    信号采集程序
    /*配置TIM2为外部触发输入捕获*/
    TIM_ETRConfig(TIM2,TIM_ExtTRGPSC_OFF,TIM_ExtTRGPolarity_Inverted,0)；//TIM2的时钟
    源选择外部触发输入捕获；无预分频器，即捕获每一个上升沿
    TIM_SetCounter(TIM2,0)；
    TIM_Cmd(TIM2,ENABLE)；//使能TIM2
    信号处理程序
    if(Main_Thread＝＝1)
    {
    temp＝TIM_GetCounter(TIM2)；//频率f
    temp2＝1000000000000/(temp*0.693*32400*3)；//电容值
    sprintf(b,"Pmt:％.3f",temp2*0.005/(0.082*0.082*8.85))；//相对介电常数
    Main_Thread＝0；
    TIM_SetCounter(TIM2,0)；//设置TIM2数值为0
    。
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