以下是我的ADC初始化程序
SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);//开启ADC时钟
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);//开启相应ADC引脚时钟
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);//开启相应ADC引脚时钟
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);//开启相应ADC引脚时钟
SysCtlPeripheralEnable(SYSCTL_PERIPH_EEPROM0);
GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3 | GPIO_PIN_2 | GPIO_PIN_1 | GPIO_PIN_0);//通道引脚初始化
GPIOPinTypeADC(GPIO_PORTD_BASE, GPIO_PIN_7 | GPIO_PIN_6 | GPIO_PIN_5 | GPIO_PIN_4);//通道引脚初始化

ADCSequenceConfigure(ADC0_BASE, ADC_SS0, ADC_TRIGGER_PROCESSOR, 0);//ADC模式配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS0, 0, ADC_CTL_CH0);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS0, 1, ADC_CTL_CH1);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS0, 2, ADC_CTL_CH2);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS0, 3, ADC_CTL_CH3);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS0, 4, ADC_CTL_CH4);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS0, 5, ADC_CTL_CH5);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS0, 6, ADC_CTL_CH6);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS0, 7, ADC_CTL_CH7 | ADC_CTL_IE | ADC_CTL_END);//采样通道配置
ADCSequenceEnable(ADC0_BASE, ADC_SS0); //使能采样序列

ADCIntClear(ADC0_BASE, ADC_SS0); //清除中断标志
ADCIntRegister(ADC0_BASE, ADC_SS0,ADC_SS0_pfnIntHandler);//注册ADC中断函数
ADCIntEnable(ADC0_BASE, ADC_SS0);
IntEnable(INT_ADC0SS0);

/*****ADC0_SS2初始化******/
GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_5 | GPIO_PIN_4);//通道引脚初始化
GPIOPinTypeADC(GPIO_PORTB_BASE, GPIO_PIN_5 | GPIO_PIN_4);//通道引脚初始化
ADCSequenceConfigure(ADC0_BASE, ADC_SS2, ADC_TRIGGER_PROCESSOR, 0);//ADC模式配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS2, 0, ADC_CTL_CH8);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS2, 1, ADC_CTL_CH9);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS2, 2, ADC_CTL_CH10);//采样通道配置
ADCSequenceStepConfigure(ADC0_BASE, ADC_SS2, 3, ADC_CTL_CH11 | ADC_CTL_IE | ADC_CTL_END);//采样通道配置
ADCSequenceEnable(ADC0_BASE, ADC_SS2); //使能采样序列
ADCIntClear(ADC0_BASE, ADC_SS2); //清除中断标志
ADCIntRegister(ADC0_BASE, ADC_SS2,ADC_SS2_pfnIntHandler);//注册ADC中断函数
ADCIntEnable(ADC0_BASE, ADC_SS2);
IntEnable(INT_ADC0SS2);
/***********/

IntMasterEnable();
开启了ADC0的12个通道同时采集，发现检测值与实际值越差越大。下图可作对比：


红 {MOD}是检测值，蓝 {MOD}是万用表测的。
请问这是什么原因？