STM32f103 四通道做ADC采样，采样结果异常

使用 STM32做ADC电流采样，4通道，发现当只有一个通道输入电流和四个通道都有电流输入的时候，采样结果会有差异。比如通道1输入3mA电流，其它通道都输入0mA，这时候1通道采样值为2.975mA，当1通道输入仍为3mA，其它通道都输入20mA，这时候的1通道采样值为2.896mA.检测过运放输出端的电压在两种情况下都没有发生改变，采样值却发生了改变。
有没有哪位大神解决过这样的问题?

驱动代码如下，理论上驱动代码应该不会有问题的
ADC_InitTypeDef ADC_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;

ADC_DeInit(ADC1); //ADC1 DeInit

RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_GPIOC, ENABLE); //ADC1 Periph and GPIOC Periph clock enable

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;//Configure ADC Channel 10-13 as analog input
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
GPIO_Init(GPIOC, &GPIO_InitStructure);

/* ADC1 configura tion ------------------------------------------------------*/
ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
ADC_InitStructure.ADC_ScanConvMode = ENABLE;
ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_NbrOfChannel = 4;
ADC_Init(ADC1, &ADC_InitStructure);

ADC_RegularChannelConfig(ADC1, ADC_Channel_10, 1, ADC_SampleTime_55Cycles5);
ADC_RegularChannelConfig(ADC1, ADC_Channel_11, 2, ADC_SampleTime_55Cycles5);
ADC_RegularChannelConfig(ADC1, ADC_Channel_12, 3, ADC_SampleTime_55Cycles5);
ADC_RegularChannelConfig(ADC1, ADC_Channel_13, 4, ADC_SampleTime_55Cycles5);

ADC_DMACmd(ADC1, ENABLE); //Enable ADC1 DMA

ADC_Cmd(ADC1, ENABLE); // Enable ADC1

ADC_ResetCalibration(ADC1); //Enable ADC1 reset calibration register

while(ADC_GetResetCalibrationStatus(ADC1)); //Check the end of ADC1 reset calibration register

ADC_StartCalibration(ADC1); //Start ADC1 calibration

while(ADC_GetCalibrationStatus(ADC1)); //Check the end of ADC1 calibration

ADC_SoftwareStartConvCmd(ADC1, ENABLE); //Start ADC1 Software Conversion


DMA_InitTypeDef DMA_InitStructure;
/* DMA1 clock enable */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1 , ENABLE);

/* DMA1 Channel1 Config */
DMA_DeInit(DMA1_Channel1);
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)ADC1_DR_Address; //ADC1->DR
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)ConvData_Tab;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = ADC_TIMES_ALL ;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel1, &DMA_InitStructure);
/* DMA1 Channel1 enable */
DMA_Cmd(DMA1_Channel1, ENABLE);