随着输入电压的增大，误差也随之增大，输入1v偏差在0.1v，输入2v偏差在0.2v，采样值大概是实际值的0.95。请问应该怎么解决
AD配置
GPIO_StructInit(&GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1| GPIO_Pin_2 | GPIO_Pin_4 ;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
DMA_DeInit(DMA1_Channel1);
DMA_StructInit(&DMA_InitStructure);
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&ADC1->DR;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)AD_Value;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = CNL * NOFCHANEL;
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);
ADC_DeInit(ADC1);
ADC_StructInit(&ADC_InitStructure);
ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConvEdge_None;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_ScanDirection = ADC_ScanDirection_Upward;
ADC_Init(ADC1, &ADC_InitStructure);
RCC_ADCCLKConfig(RCC_ADCCLK_PCLK_Div4);
ADC_ChannelConfig(ADC1, ADC_Channel_0 , ADC_SampleTime_239_5Cycles);
ADC_ChannelConfig(ADC1, ADC_Channel_1 , ADC_SampleTime_239_5Cycles);
ADC_ChannelConfig(ADC1, ADC_Channel_2 , ADC_SampleTime_239_5Cycles);
ADC_ChannelConfig(ADC1, ADC_Channel_4 , ADC_SampleTime_239_5Cycles);
ADC_GetCalibrationFactor(ADC1);
ADC_DMARequestModeConfig(ADC1, ADC_DMAMode_Circular);//开启循环模式
DMA_Cmd(DMA1_Channel1, ENABLE);
DMA_ITConfig(DMA1_Channel1, DMA_IT_TC, ENABLE);
ADC_DMACmd(ADC1, ENABLE);
ADC_Cmd(ADC1, ENABLE);
while(ADC_GetFlagStatus(ADC1,ADC_FLAG_ADEN) == RESET);
ADC_StartOfConversion(ADC1);
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