电容测量报告

评阅成绩2014年湖南省大学生电子设计竞赛设计报告题号：A)竞赛题名称： 基于LM3S811实现的电容参数测量仪参赛队编号： 0908 评阅人签名： 2014年8月24日基于LM3S811实现的电容参数测试仪摘要本系统采用键盘和CD4052模拟开关联合控制的方法实现对电容参数的测量。同时系统以TI公司的LM3S811为核心，使用TLV7211产生方波，由控制器对方波数据进行处理并显示。在达到基本要求的基础上，系统还能够测量一定范围电容的ESR。一、 设计思路描述总体方案系统包括：电压转化模块、显示模块、按键模块、控制模块等。系统总体框图如图1所示。图1总体方案图方波产生模块方案一：采用555定时器及外接RC电路产生方波，但是在仿真中发现该方案仅适用于中档大小的电容，对于较大或较小的电容无法产生准确的波形，故舍弃此方案。方案二：采用TLV7211产生方波，由输出端向电容进行充电，当电容电压高于某一值时，输出端电压产生翻转，从而产生方波。所产生方波的频率由R和Cx共同决定，即f=1/(2*ln2*R*Cx),通过模拟开关切换电阻来产生不同的档位，经过仿真，此法可以测量题目要求的电容范围，故采用之。电压转化模块方案一：通过电阻分压来获得+5V电压，此法电路简单，但由于功率较低，带动负载能力相对较差，不能满足系统要求，故舍之。方案二：采用三端稳压芯片加电容滤波，此法电压值稳定带负载能力强，可以满足系统的需求，故采用之。二、 硬件系统设计方波产生电路利用TLV7211制作比较器，产生方波，原理图如下：

100们50kQ1MQ100们50kQ1MQ10kQ图2方波产生电路图控制器通过I/O口采集到输出端输出的方波，通过计算得到电容值电压转化电路5VGND5VGND3.ESR测量电路三、 算法数学描述1.档位电阻的选择待测电容Cx=l/(2*ln2*R*f),首先，选定待测电容Cx的范围，通过调节单位电阻R的值，使频率f满足一个合适的测量范围。2.频率的测量使用定时器0定时200ms,定时器1A设置为输入计数模式用来计录上升沿个数，当定时器0记

时完毕，假设定时器A1所记上升沿个数为n,若n〉2000，则说明此频率较高，适合输入计时模式,从而直接计算频率。若n〈=2000,则说明频率较低，记录上升沿个数可能导致误差较大，故设置定时器1A为输入计时模式，计算两个上升沿之间的时间，从而测得频率。ESR测量原理使用单片机PWM模块产生lOOKHz方波，利用电容节滤波，电阻分压产生峰峰值为250V方波，将待测电容视为电阻，通过放大器加直流偏置并放大信号，后又滤去直流电压，再一次加直流偏置并进行峰值检测，最后与一电阻分压，通过读取分压值可以算得电容阻值。四、 系统软件流程图 如下图所示。部分源程序见附录E.开始主函数框图启动timerO启动timerlA电容测试函数框图开始主函数框图启动timerO启动timerlA电容测试函数框图五、 测试方法测试使用的仪器EM1716型三路直流稳定电源、TektronixTDS1012100MHz示波器、万用表、M8电容测试仪测试方法（1） 记录标注电容、对应电阻、计算频率、测量频率、测算电容并计算电容误差。（2） 记录加模拟开关后的对应电阻、计算频率、测算电容及误差。（3） 进行软件调试，记录电容标注值、电容测试仪测量值、系统显示值、测试误差。以上测试结果分别由表1、表2、表3记录，详见附录A。六、 指标测试和测试结果表1标注电容电阻计算频率测量频率测算电容测量误差1.00E-0910000009.72163E-10721.3445863742-0.0278374852.20E-0910000002.19254E-09327.8839029329-0.003392392

3.30E-0910000003.08267E-09218.5892686234-0.065857827表2标注电容电阻（加模拟开关）测量频率计算频率测算电容测试误差1.00E-091000300714721.12824781.00998E-090.009983542.20E-091000300326327.78556722.21205E-090.00547723.30E-091000300233218.52371153.09497E-09-0.062129994表3标注电容电容测试仪测量值系统显示值测试误差（相对测试仪）误差（相对标注值）4.70E-084.83E-084.61E-08-0.045548654-0.0191489366.80E-087.02E-086.75E-08-0.038324548-0.0073529411.00E-071.07E-071.03E-07-0.0337078650.032七、 数据分析与结论经实际测试，本系统可以在33pF-470uF的范围内实现电容参数的测量，而且测量结果较准确，同时可以在一定范围内实现ESR的测量。系统通过键盘进行人机交互，具备LCD显示功能。采用供电电压3.3v的LCD液晶显示测量数据。系统较好地实现了题目的基本要求和部分提高要求。附录A：表1标注电容F电阻Q测算电容F计算频率Hz测量频率Hz电容误差％l.OOE-1110000002.67165E-1172134.45863270001.6716466162.20E-1110000004.02986E-1132788.39029179000.8317536473.30E-1110000005.09784E-1121858.92686141500.5448004851.00E-1010000001.16534E-117213.44586361900-0.8834661412.20E-1010000002.40448E-103278.83902930000.0929463433.30E-1010000003.60672E-102185.89268620000.0929463434.70E-1010000004.89047E-101534.77571614750.0405259096.80E-1010000007.21345E-101060.80086210000.0608008621.00E-0910000009.72163E-10721.3445863742-0.0278374852.20E-0910000002.19254E-09327.8839029329-0.0033923923.30E-0910000003.08267E-09218.5892686234-0.0658578274.70E-0910000004.80896E-09153.47757161500.023183815.60E-0910000006.38358E-09128.81153331130.1399250731.00E-0810000001.0117E-0872.1344586371.30.0117034872.20E-0810000002.4874E-0832.78839029290.1306341483.30E-0810000001.20425E-0921.85892686599-0.9635076353.30E-08496002.42792E-08440.7041705599-0.2642668274.70E-08496004.60229E-08309.4305878316-0.0207892796.80E-08496006.7643E-08213.8711416215-0.0052505041.00E-07496001.03144E-07145.43237631410.0314352932.20E-07496002.08655E-0766.1056255869.7-0.0515692173.30E-07496003.23183E-0744.0704170545-0.0206573994.70E-07496004.19113E-0730.9430587834.7-0.1082691996.80E-07496006.61056E-0721.3871141622-0.0278584476.80E-0797306.56072E-07109.0237268113-0.0351882581.00E-0697319.50366E-0774.128515778-0.0496344141.00E-0597301.11316E-057.4136134266.660.1131551691.00E-051001.17674E-05721.34458636130.1767448391.00E-041000.00010766372076633711

2.20E-041000.0002487432.78839029290.1306341484.70E-041000.00042937215.3477571616.8-0.086443026表2标注电容F电阻（加模拟开关）测量频率计算频率测算电容测试误差1.00E-1110003002.20E-1110003003.30E-1110003001006021852.371157.16827E-111.1722038911.00E-10100030052707211.2824781.36836E-100.3683647972.20E-10100030027833277.8556722.59119E-100.1778137523.30E-10100030018822185.2371153.83171E-100.1611249284.70E-10100030014091534.3154215.11801E-100.0889392636.80E-1010003009761060.4827177.38861E-100.0865601611.00E-091000300714721.12824781.00998E-090.009983542.20E-091000300326327.78556722.21205E-090.00547723.30E-091000300233218.52371153.09497E-09-0.0621299944.70E-091000300150153.43154214.80752E-090.0228769476.50E-091000300113110.94280746.38167E-09-0.0182052451.00E-08100030068.372.112824781.05582E-080.0558246672.20E-08100030026.732.778556722.70085E-080.22766133.30E-08100030019.921.852371153.62376E-080.0981091033.30E-0849900398438.05464643.63211E-080.1006398154.70E-0849900314307.57028374.60376E-08-0.0204768046.80E-0849900226212.58534316.39637E-08-0.0593568891.00E-0749900143144.55803331.0109E-070.0108953382.20E-074990066.165.708196972.18696E-07-0.0059274293.30E-074990044.643.805464643.24121E-07-0.0178146944.70E-074990034.330.757028374.21452E-07-0.1032936346.80E-074990021.921.258534316.60082E-07-0.0292906716.80E-0710030108105.76279786.65914E-07-0.0207148351.00E-06100307471.918702529.71874E-07-0.0281256421.00E-05100306.47.1918702521.12373E-050.1237297271.00E-05400167.8180.33614661.07471E-050.0747088591.00E-0440018.318.033614669.85443E-05-0.0145565762.20E-0440088.1970975720.000225420.0246371964.70E-0440043.8369392890.00045084-0.040765178

表3标注电容FM8测试值F系统显示值测试误差（相对测试仪）误差（相对标注）3.30E-113.50E-117.20E-111.0571428571.1818181821.00E-101.01E-101.73E-100.7128712870.732.20E-102.24E-102.58E-100.1517857140.1727272733.30E-103.52E-103.81E-100.0823863640.1545454554.70E-104.83E-105.08E-100.0517598340.0808510646.80E-107.13E-107.30E-100.0235624120.0732352941.00E-091.01E-091.02E-090.0049358340.0182.20E-092.25E-092.21E-09-0.018633540.0054545453.30E-093.39E-093.32E-09-0.0194747710.0069696974.70E-094.88E-094.78E-09-0.0215163930.0159574475.60E-096.59E-096.44E-09-0.0232134730.1496428571.00E-081.05E-081.02E-08-0.0290630980.01562.20E-082.79E-082.77E-08-0.0044867190.2606818183.30E-083.44E-083.43E-08-0.0011925540.0405757584.70E-084.83E-084.61E-08-0.045548654-0.0191489366.80E-087.02E-086.75E-08-0.038324548-0.0073529411.00E-071.07E-071.03E-07-0.0337078650.0322.20E-072.19E-072.13E-07-0.028793419-0.0340909093.30E-073.41E-073.29E-07-0.036656891-0.0045454554.70E-074.58E-074.52E-07-0.014185945-0.038936176.80E-077.09E-076.88E-07-0.0290591060.0122058821.00E-061.00E-069.64E-07-0.038223553-0.03632.20E-062.22E-062.12E-06-0.047297297-0.0386363643.30E-063.35E-063.27E-06-0.024179104-0.0093939391.00E-051.12E-051.20E-050.0682709450.19862.20E-052.48E-052.40E-05-0.0325706210.0896772733.30E-053.68E-053.35E-05-0.0901683870.0151515154.70E-054.80E-054.76E-05-0.0089527380.0127659571.00E-041.03E-041.07E-040.0309777350.0652.20E-042.31E-042.26E-04-0.01949740.0286363643.30E-043.40E-043.62E-040.065921130.0975757584.70E-044.72E-046.03E-040.2780839340.282978723附录B：频率测量程序//频率测量//范围200hz到2.5Mhz#include"frequence.h"#include"inc/hw_types.h"#include"driverlib/debug.h"#include"driverlib/sysctl.h"#include"drivers/display96x16x1.h"#include"driverlib/gpio.h"#include"driverlib/pin_map.h"#include"inc/hw_memmap.h"#include"inc/hw_gpio.h"#include"utils/uartstdio.h"#include"driverlib/timer.h"#include"math.h"//用来记录TimerlA溢出的次数unsignedlongg_ulTimer1ATimeoutCount=0;//初始化与测频相关的外设voidFreqMeasureInit(void){//将PD5设为CCP引脚CCP2SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);GPIOPinTypeTimer(GPIO_PORTD_BASE,GPIO_PIN_5);//ccp2//使能TimerO，设为32位单次触发模式，TimerO用于定时SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);TimerConfigure(TIMERO_BASE,TIMER_CFG_32_BIT_OS);//使能Timer1ASysCtlPeripheralEnable(SYSCTL_PERIPH_TIMERl);//Timer1A捕捉上升沿即ccp2TimerControlEvent(TIMER1_BASE,TIMER_A,TIMER_EVENT_POS_EDGE);//测量ulMS毫秒内输入的信号上升沿数unsignedlongGetEdgeCount(unsignedlongulMS){unsignedlongulValue;//设置Timer0定时器，定时ulMS毫秒TimerLoadSet(TIMER0_BASE,TIMER_A,(SysCtlClockGet()/1000)*ulMS-1);//配置Timerl，将TimerlA设置为输入计数模式TimerConfigure(TIMER1_BASE,TIMER_CFG_16_BIT_PAIR|TIMER_CFG_A_CAP_COUNT);TimerLoadSet(TIMERl_BASE,TIMER_A,0xfffe);//装载初值65534//将匹配寄存器设置为比装载寄存器大的值//这样就不会产生匹配中断，Timer1A对输入信号上升沿循环计数TimerMatchSet(TIMERl_BASE,TIMER_A,0xffff);g_ulTimerlATimeoutCount=0;//使能两个TimerTimerEnable(TIMERl_BASE,TIMER_A);TimerEnable(TIMER0_BASE,TIMER_A);//检测Timer。是否溢出while(!(TimerIntStatus(TIMER0_BASE,false)&TIMER_TIMA_TIMEOUT)){//检测TimerlA是否溢出if((TimerIntStatus(TIMERl_BASE,false)&TIMER_TIMA_TIMEOUT)){//若TimerlA溢出，清除溢出标志位，g_ulTimer1ATimeoutCount++TimerIntClear(TIMERl_BASE,TIMER_TIMA_TIMEOUT);g_ulTimerlATimeoutCount++;}}//定时结束，禁能TimerlATimerDisable(TIMERl_BASE,TIMER_A);ulValue=TimerValueGet(TIMERl_BASE,TIMER_A); //读取TimerlA计数值TimerintClear(TIMERO_BASE,TIMER_TIMA_TIMEOUT);//清除TimerO溢出标志位//计算ulMS毫秒内输入上升沿个数并返回g_ulTimer1ATimeoutCount++;returng_ulTimer1ATimeoutCount*65535-ulValue;}//测量两个输入信号上升沿的时间间隔(系统时钟个数)unsignedlongGetEdgePeriod(void){unsignedlongulFirstEdgeTime; //第一个上升沿到达时TimerlA的计数值unsignedlongulSecondEdgeTime; //第二个上升沿到达时Timer1A的计数值//配置Timer1A为输入定时模式TimerConfigure(TiMERl_BASE,TiMER_CFG_l6_BiT_PAiR|TiMER_CFG_A_CAP_TiME);TimerLoadSet(TIMER1_BASE,TIMER_A,0xffff);//装载值设为0xffffTimerEnable(TIMER1_BASE,TIMER_A);//使能Timer1AUARTprintf("ll\r");//当第一个输入事件到达时，将计数器计数值存入ulFirstEdgeTimewhile(!(TimerintStatus(TiMERl_BASE,false)&TiMER_CAPA_EVENT));UARTprintf("22\r");ulFirstEdgeTime=TimerValueGet(TiMERl_BASE,TiMER_A);g_ulTimer1ATimeoutCount二0; //清零g_ulTimer1ATimeoutCount//清除溢出以及输入捕捉中断标志位TimerintClear(TiMERl_BASE,TiMER_CAPA_EVENT|TiMER_TiMA_TiMEOUT);//等待下一个输入事件到达while(!(TimerintStatus(TiMERl_BASE,false)&TiMER_CAPA_EVENT)){//如果Timer1A产生溢出，g_ulTimer1ATimeoutCount++并清除Timer1A溢出标志位if((TimerintStatus(TiMERl_BASE,false)&TiMER_TiMA_TiMEOUT)){TimerintClear(TiMERl_BASE,TiMER_TiMA_TiMEOUT);g_ulTimerlATimeoutCount++;}}//禁能Timer1ATimerDisable(TiMERl_BASE,TiMER_A);//记录第二个时间发生时间ulSecondEdgeTime=TimerValueGet(TiMERl_BASE,TiMER_A);TimerIntClear(TIMER1_BASE,TIMER_CAPA_EVENT);//返回两个输入事件的时间间隔(系统时钟数目)return(g_ulTimer1ATimeoutCount*65536+ulFirstEdgeTime-ulSecondEdgeTime);}//测量输入信号频率//unsignedlong*Int指向频率整数部分的指针//unsignedlong*Frac指向频率小数部分的指针voidFreqMeasure(unsignedlong*Int,unsignedlong*Frac){unsignedlongulCount;ulCount=GetEdgeCount(200);//测量200ms内输入的事件数if(ulCount<2000)//如果输入事件数小于2000个，则测量两个输入事件的时间间隔{ulCount=GetEdgePeriod();//记录时间间隔*Int=(SysCtlClockGet()*1000.0)/ulCount/1000;//计算频率(低频)*Frac=(unsignedlong)((SysCtlClockGet()*1000.0)/ulCount)%1;}else{*Int=ulCount*5;//计算频率(高频)*Frac=0;}}档位切换程序#include"inc/hw_types.h"#include"driverlib/debug.h"#include"driverlib/sysctl.h"#include"drivers/display96x16x1.h"#include"driverlib/gpio.h"#include"driverlib/pin_map.h"#include"inc/hw_memmap.h"#include"inc/hw_gpio.h"#include"utils/uartstdio.h"#include"lcd12864s.h"#include"driverlib/timer.h"#include"inc/hw_ints.h"#include"driverlib/interrupt.h"#include"stdio.h"#include"frequence.h"#include"math.h"#include"TLV5616DA.h"/// /^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js^js//#defineKEY_PERIPHSYSCTL_PERIPH_GPIOC#defineKEY_PORTGPIO_PORTC_BASE#defineKEY_PINGPIO_PIN_4#defineR3300#defineR2300#defineR1300#defineR0300//防止jtag接口死锁voidjtagWait(){SysCtlPeripheralEnable(KEY_PERIPH);GPIOPinTypeGPIOInput(KEY_PORT,KEY_PIN);if(GPIOPinRead(KEY_PORT,KEY_PIN)==0x00){while(1);}SysCtlPeripheralDisable(KEY_PERIPH);}unsignedlongTheSysClock=12000000UL;unsignedlongInt;//指向频率整数部分的指针unsignedlongFrac;//指向频率小数部分的指针doublef=0; //测量频率doublec_val=0.0;//测量电容值intflag=0; //档位标志doublecal(doublefre,intfla){/*计算电容的函数*/doublec;if(fla==3){c=l/(2*fre*log(2)*(1000000+R3)); //计算公式c=/(2*f*R*ln2)//此处为1M电阻c=c*1000000000000; //换算成pf级Show_LCD12864(0x98,〃档位为3");}if(fla==2){c=1/(2*fre*(49600+R2)*log(2)); //此处为50k电阻c=c*1000000000; //换算成nf级Show_LCD12864(0x98,〃档位为2〃)；}if(fla==1){c=l/(2*fre*(9730+Rl)*log(2)); //此处为lk电阻c=c*1000000000; //换算成nf级Show_LCD12864(0x98,〃档位为1");}if(flag==0){c=1/(2*fre*(98.3+R0)*log(2)); //计算出的单位为mfc=c*100000; //换算成ufShow_LCD12864(0x98,〃档位为0");}returnc;}voiddisplay(doubleval){ /*串口显示函数*/inti;charcval[10];i=val;sprintf(cval,"%d",i);UARTprintf(cval);WriteCmd_LCD12864s(0x01); //清除显示SysCtlDelay(10*(TheSysClock/3000));Show_LCD12864(0x90,cval);i=(val-i)*100;sprintf(cval,".%d",i);UARTprintf(cval);Show_LCD12864(0x92,cval);if(flag==3){UARTprintf("pf\r");TOC\o"1-5"\h\zShow_LCD12864(0x93,"pf"); }if(flag==1|flag==2){UARTprintf("nf\r");Show_LCD12864(0x93,"nf"); }if(flag==0){UARTprintf("uf\r");Show_LCD12864(0x93,"uf"); }}

voidchange1(doublef1){/**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X* //if(flag==2&&f1<15){//使用2通道GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0,0Xff);//A=1,B=0GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_1,0X00);flag=1;}if(flag==2&&f1>350){GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0|GPIO_PIN_1,0Xff);//A=1,B=1flag=3;}if(flag==3&&f1<17){GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0,0X00);//A=0,B=1GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_1,0Xff);flag=2;}if(flag==1&&f1>115){GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0,0X00);//A=0,B=1GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_1,0Xff);flag=2;}if(flag==1&&f1<50){GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0|GPIO_PIN_1,0X00);//使用0通道flag=0;}if(flag==0&&f1>180){//使用1通道//A=0,B=1挡函GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0,0Xff);//A=0,B=1挡函GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_1,0X00);flag=1;}}voidchange2(doublef1){/*换*X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**X**i**i**i**i**i**i**i**i**i**i**i**i**i**i**i**i**i**i**i**i*//if(flag==2&&f1<15){//使用2通道GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0,0Xff);//A=1,B=0GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_1,0X00);flag=1;if(flag==2&&f1>350){GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0|GPIO_PIN_1,0Xff);//A=1,B=1flag=3;}if(flag==3&&f1<17){GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0,0X00);//A=0,B=1GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_1,0Xff);flag=2;}if(flag==1&&f1>115){GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_0,0X00);//A=0,B=1GPIOPinWrite(GPIO_PORTB_BASE,GPIO_PIN_1,0Xff);flag=2;}}doubleensure(doublec,doublef){/*修正误差函数*///change(f);if(flag==0){if(f>9000)c=c-24;if(f>1400&&f<=9000)c=c-30;}returnc;}voidGPIOinit(void){GPIOPadConfigSet(GPIO_PORTC_BASE,GPIO_PIN_4,GPIO_STRENGTH_2MA,GPIO_PIN_TYPE_STD_WPU);//设置PC4为2MA,上拉输入GPIODirModeSet(GPIO_PORTC_BASE,GPI0_PIN_4,GPI0_DIR_M0DE_IN);//设置GPIO输入模式GPIOIntTypeSet(GPIO_PORTC_BASE,GPI0_PIN_4,GPIO_LOW_LEVEL);//设置GPIO中断GPIOPinIntEnable(GPIO_PORTC_BASE,GPIO_PIN_4);//使能KEY所在管脚的中断IntEnable(