ads1118实现热电偶测温

文章目录

ads1118实现热电偶测温
前言
一、热电偶是什么及测温原理
二、热电偶测温流程
- 1.用到的基本公式及基本流程：
- 2.ADS1118读取数据：
- 3.温度转换

前言

ads1118实现热电偶测温。内容包括：了解热电偶的基本原理；ads1118的adc转换及原理；电偶测试实现；滤波算法

一、热电偶是什么及测温原理

热电偶测温利用的是“热效应”的原理。当有两种不同的导体或者半导体A和B组成一个回路，其两端相互连接时，只要两节点处的温度不同，就会形成电动势，这两个端分别称为“冷端”、“工作端”。因而我们要实现一个完整的热电偶测量过程，就需要测量工作端的ADC值和冷端的温度值。

二、热电偶测温流程

1.用到的基本公式及基本流程：

Created with Raphaël 2.2.0开始启动设置ADS1118初始化启动测量ads1118的ADC并且转化成电压V1启动测试ads1118的内部温度程序查表：热电偶的电压温度转换表（网上能查找到）内部温度T0转化电压V0，V=（V1+V0）[这个为冷端补偿过程]查表将V转换为温度T就是最终的温度了。如果要细化的小数位，一度内的数据线性比例求值就好。

2.ADS1118读取数据：

ADS1118的通讯接口是SPI，SPI的通讯原理及过程就不在这里赘述了。ADS1118内部集成东西比较多，内部温度、可编程运放、16位的ADC，并且设置过程比较简单，里面只有一个寄存器。 ![在这里插入图片描述](https://img-blog.csdnimg.cn/2021021309252434.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2NjAwNjgy,size_16,color_FFFFFF,t_70)

实现代码如下：

//read once to get data
/********************************************************** @function  Ads1118_ReadData_one* @role      读取一组数据* @input     none* @output    none* @return    none********************************************************/
void Ads1118_ReadData_one(unsigned int* ReadBDate)
{unsigned int temp,temp1,temp2;ads_spi_sck_off();ads1118_delay(10);ads_spi_cs_off();ads1118_delay(50);if(FistEn==1)//the fist time no data to conver{if(ads_spi_do()==1)while(ads_spi_do());}else{FistEn=1;}temp1=Ads_SpiReadU16(0x8ffb);//T command now is AD,and next is T//temp1=ReadU16(0x8f9b);//T command now is AD,and next is TReadBDate[0]=temp1;ads_spi_cs_on();//temp=ReadU16(0xffff);ads1118_delay(50);ads_spi_sck_off();ads1118_delay(10);ads_spi_cs_off();if(ads_spi_do()==1)while(ads_spi_do());temp2=Ads_SpiReadU16(0x8feb);//AD command now is T,and next is AD  0x8feb//temp2=ReadU16(0x8f8b);//AD command now is T,and next is ADReadBDate[1]=temp2;ads_spi_cs_on();ads1118_delay(50);ads_spi_sck_off();ads1118_delay(10);ads_spi_cs_off();if(ads_spi_do()==1)while(ads_spi_do());temp2=Ads_SpiReadU16(0xBfeb);//AD command now is T,and next is AD,start ant2ReadBDate[2]=temp2;ads_spi_cs_on();
}/********************************************************** @function  Ads1118_ReadData* @role      读取一次数据* @input     none* @output    通道2的adc，内部温度，通道1的adc* @return    none********************************************************/
unsigned int Ads1118_ReadData(unsigned int* ReadBDate)
{char i ,j;int Data_1[DataCout];int Data_2[DataCout];int Data_3[DataCout];unsigned int TemData[3];long  temd;//unsigned int dataCou=20;for(i=0;i<DataCout;i++){Ads1118_ReadData_one(TemData);Data_1[i] = TemData[0];Data_2[i] = TemData[1];Data_3[i] = TemData[2];}for(i=DataCout-1;i>0;i--){for(j=0;j<i;j++){if( Data_1[j+1] > Data_1[j] ) {TemData[0]  =Data_1[j+1];Data_1[j+1] =Data_1[j];Data_1[j]   =TemData[0];}}}temd=0;for(i=0;i<(DataCout-6);i++){temd+=(long ) Data_1[i+3];}ReadBDate[0]=temd/(DataCout-6);//ReadBDate[0]=Data_1[5];for(i=DataCout-1;i>0;i--){for(j=0;j<i;j++){if(Data_2[j+1]>Data_2[j]) {TemData[1]  =Data_2[j+1];Data_2[j+1] =Data_2[j];Data_2[j]   =TemData[1];}}}temd=0;for(i=0;i<(DataCout-6);i++){temd +=(long )Data_2[i+3];}ReadBDate[1]= temd/(DataCout-6)  ;for(i=DataCout-1;i>0;i--){for(j=0;j<i;j++){if(Data_3[j+1]>Data_3[j]) {TemData[1]  =Data_3[j+1];Data_3[j+1] =Data_3[j];Data_3[j]   =TemData[1];}}}temd=0;for(i=0;i<(DataCout-6);i++){temd +=(long )Data_3[i+3];}ReadBDate[2]= temd/(DataCout-6)  ;//ReadBDate[1]=Data_2[5];return 0;}

3.温度转换

代码如下：

/********************************************************** @function  Conver_to_T* @role      传感器热电偶温度转换* @input     none* @output    none* @return    none********************************************************/
long Conver_to_T(unsigned int coldJT,unsigned int TU,unsigned char Dire)
{   unsigned int i;//,GetT;long GetT;unsigned int ColdJU,NewTU;ColdJU=ThermocoupleCV[(coldJT/100)+1]+(coldJT%100+1)*4/10;// (coldJT%100)/40*100if(Dire)NewTU=ColdJU+TU;   //positive voltageelse                    //negative voltage{if(ColdJU>=TU){NewTU=ColdJU-TU;      }else{NewTU=TU-ColdJU;  }}if(NewTU>50){GetT=NewTU/50;}else{GetT=0;}if( (Dire==0) && (ColdJU<TU) ) //<0{for(i=GetT;(NewTU>ThermocoupleCV_Cold[i]);i++);if(i==0) i++;GetT=i-1;GetT*=100;GetT+=( NewTU-ThermocoupleCV_Cold[i-1] )*100 / ( ThermocoupleCV_Cold[i]-ThermocoupleCV_Cold[i-1] );//make it's valuse close to device only. It could be delete,if want to more close to real.GetT+=(i-1)/2;GetT+=50;// e=ax+y;a=0.5,b=0.5//make it's valuse close to devicereturn GetT;  //real T*100}else{for(i=GetT;(NewTU>ThermocoupleCV[i]);i++);if(i==0) i++;GetT=i-1;GetT*=100;GetT+=( NewTU-ThermocoupleCV[i-1] )*100 / ( ThermocoupleCV[i]-ThermocoupleCV[i-1] );//make it's valuse close to device only. It could be delete,if want to more close to real.GetT+=(i-1)/100*10;if(GetT>=50)GetT-=50;// e=ax+y;a=1,b=-0.5 //make it's valuse close to devicereturn GetT;  //real T*100}}/********************************************************** @function  RegValueToTemp* @role      传感器值转换最终温度* @input     none* @output    none* @return    none********************************************************/
int RegValueToTemp(unsigned int RegValueCodeT,unsigned int RegValueADC)
{unsigned int McoldJT=0,MJU=0,tem=0;int RealT=0;RegValueCodeT>>=2;RegValueCodeT&=0xfff0;tem=RegValueCodeT*3;//conver to T number  *100   /* 数据只有14位且左对齐 0.03125约等于0.03 */McoldJT=tem;if(RegValueADC&0x8000){RegValueADC=~RegValueADC;RegValueADC=RegValueADC+2;RegValueADC&=0x7fff;//     tem-=(long)RegValueADC*781/40;
//      tem-=5;
//      tem/=10;/ negative voltage//new conver//McoldJT+=50;//McoldJT/=100;MJU=((long)RegValueADC*781+50)/100;RealT=Conver_to_T(McoldJT,MJU,0);  //had real T*100}else{//      tem+=(long)RegValueADC*781/40;//AdData[0]*700/40
//      tem+=5;
//      tem/=10;/ //positive voltage//new conver//McoldJT+=50;//McoldJT/=100;MJU=((long)RegValueADC*781+50)/100;RealT=Conver_to_T(McoldJT,MJU,1); //had real T*100}return RealT;}

最后附上stm32的spi驱动参考：

void ads1118_delay(unsigned char i)
{i=i*10;while(i--);
}/********************************************************** @function  GpioCfg* @role      配置管脚* @input     none* @output    none* @return    none********************************************************/
static void GpioCfg_out( GPIO_TypeDef* GPIO,uint32_t Pin)
{GPIO_InitTypeDef GPIO_InitStruct = {0};GPIO_InitStruct.Pin = Pin;GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;GPIO_InitStruct.Pull = GPIO_PULLUP;GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;HAL_GPIO_Init(GPIO, &GPIO_InitStruct);
}/********************************************************** @function  GpioCfg* @role      配置管脚* @input     none* @output    none* @return    none********************************************************/
static void GpioCfg_int( GPIO_TypeDef* GPIO,uint32_t Pin)
{GPIO_InitTypeDef GPIO_InitStruct = {0};GPIO_InitStruct.Pin = Pin;GPIO_InitStruct.Mode = GPIO_MODE_INPUT;GPIO_InitStruct.Pull = GPIO_PULLUP;GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;HAL_GPIO_Init(GPIO, &GPIO_InitStruct);
}/********************************************************** @function  ads1118_ioCnofig* @role      管脚配置初始化* @input     none* @output    none* @return    none********************************************************/
void ads1118_ioCnofig(void)
{ADS_SPI_CS_PIN_CLK_EN();ADS_SPI_DI_PIN_CLK_EN();ADS_SPI_DO_PIN_CLK_EN();ADS_SPI_SCK_PIN_CLK_EN();GpioCfg_out(ADS_SPI_CS_PIN);GpioCfg_out(ADS_SPI_DO_PIN);GpioCfg_out(ADS_SPI_SCK_PIN);GpioCfg_int(ADS_SPI_DI_PIN);
}
/*
#define ads_spi_cs  P2.1
#define ads_spi_di  P2.2
#define ads_spi_do  P14.7
#define ads_spi_sck P2.0
*//********************************************************** @function  Ads_SpiReadU16* @role      spi的时序* @input     none* @output    none* @return    none********************************************************/
unsigned int Ads_SpiReadU16(unsigned int Cmd)
{char i;unsigned int temp=0;for(i=0;i<16;i++){temp<<=1;ads_spi_sck_on();if(Cmd&0x8000)ads_spi_di_on();else ads_spi_di_off();ads1118_delay(10);ads_spi_sck_off();if(ads_spi_do())temp|=1;ads1118_delay(10);Cmd<<=1;}return temp;
}

最后要说明一下：我这里只加了中值滤波算法，实际产品中还会加入惯性滤波算法，使显示结果更加平稳。