NTC（Negative Temperature Coefficient）是指随温度上升电阻呈指数关系减小、具有负温度系数的热敏电阻现象和材料。该材料是利用锰、铜、硅、钴、铁、镍、锌等两种或两种以上的金属氧化物进行充分混合、成型、烧结等工艺而成的半导体陶瓷，可制成具有负温度系数（NTC）的热敏电阻。其电阻率和材料常数随材料成分比例、烧结气氛、烧结温度和结构状态不同而变化。现在还出现了以碳化硅、硒化锡、氮化钽等为代表的非氧化物系NTC热敏电阻材料。
在实际电路中，则是采用分压的方式进行，该点的电压采集，其NTC设计原理图如图所示：
而图中的下面则是接NTC的接口。
下面则是ntc程序
ntc_3950.c
#include "ntc_3950.h"
#define SHORT_CIRCUIT_THRESHOLD 15
#define OPEN_CIRCUIT_THRESHOLD 4080
uint16_t DATA_BUFF1[ADC_LOOP1_MARK] = {0};
uint16_t DATA_BUFF2[ADC_LOOP2_MARK] = {0};
/*定义一个结构体类型数组：(温度-阻值)表 温度按降序填*/
const NTC_10KTYPE ntc_10k_table[] = {
125,325,
124,333,
123,342,
122,352,
121,361,
120,371,
119,381,
118,392,
117,403,
116,414,
115,426,
114,438,
113,450,
112,463,
111,476,
110,490,
109,504,
108,519,
107,534,
106,549,
105,566,
104,582,
103,600,
102,618,
101,636,
100,656,
99,675,
98,696,
97,718,
96,740,
95,763,
94,786,
93,811,
92,837,
91,863,
90,891,
89,919,
88,949,
87,980,
86,1011,
85,1045,
84,1079,
83,1114,
82,1151,
81,1190,
80,1230,
79,1271,
78,1314,
77,1359,
76,1406,
75,1454,
74,1504,
73,1557,
72,1611,
71,1668,
70,1726,
69,1788,
68,1851,
67,1918,
66,1987,
65,2059,
64,2134,
63,2212,
62,2293,
61,2378,
60,2466,
59,2558,
58,2654,
57,2755,
56,2859,
55,2968,
54,3082,
53,3201,
52,3324,
51,3454,
50,3572,
49,3730,
48,3877,
47,4031,
46,4192,
45,4360,
44,4536,
43,4720,
42,4913,
41,5114,
40,5324,
39,5545,
38,5775,
37,6017,
36,6270,
35,6534,
34,6812,
33,7103,
32,7407,
31,7727,
30,8062,
29,8413,
28,8781,
27,9168,
26,9574,
25,10000,
24,10447,
23,10916,
22,11409,
21,11928,
20,12472,
19,13045,
18,13647,
17,14280,
16,14945,
15,15646,
14,16383,
13,17160,
12,17977,
11,18838,
10,19788,
9,20700,
8,21707,
7,22769,
6,23889,
5,25071,
4,26317,
3,27633,
2,29022,
1,30490,
0,32040,
-1,33677,
-2,35409,
-3,37239,
-4,39175,
-5,41223,
-6,43391,
-7,45686,
-8,48117,
-9,50692,
-10,53420,
-11,56313,
-12,59380,
-13,62634,
-14,66087,
-15,69753,
-16,73646,
-17,77782,
-18,82178,
-19,86852,
-20,91824,
-21,97115,
-22,102747,
-23,108745,
-24,115136,
-25,121950,
-26,129215,
-27,136968,
-28,145244,
-29,154083,
-30,163528,
-31,173626,
-32,184428,
-33,195990,
-34,208371,
-35,221637,
-36,235861,
-37,251120,
-38,267501,
-39,285097,
-40,304011,
-41,324356,
-42,346255,
-43,369843,
-44,395272,
-45,422704,
-46,452323,
-47,484327,
-48,518939,
-49,556404,
-50,596993,
-51,641008,
-52,688785,
-53,740696,
-54,797157,
-55,858631,
};
uint16_t NTC_ADC(void) //ADC采集程序
{
HAL_ADC_Start(&hadc);//开始ADC采集
HAL_ADC_PollForConversion(&hadc,100);//等待采集结束
if(HAL_IS_BIT_SET(HAL_ADC_GetState(&hadc), HAL_ADC_STATE_REG_EOC))//读取ADC完成标志位
{
return HAL_ADC_GetValue(&hadc);//读出ADC数值
}
return 0;
}
//[-级ADC滤波]读1次ADC值放入以往数组，去掉最大最小值后取平均值
uint16_t adc_getavg1(uint16_t adc)
{
uint16_t maxA,minA;
uint32_t avg=0;
uint16_t jA;
maxA = 0;
minA = 0xffff;
for(jA=0;jA<(ADC_LOOP1_MARK-1);jA++) //将数据左移一位，空出【0】存新数据
{
DATA_BUFF1[(ADC_LOOP1_MARK-1)-jA] = DATA_BUFF1[(ADC_LOOP1_MARK-2)-jA];
}
DATA_BUFF1[0] = adc; //存新数据
for(jA=0;jA<ADC_LOOP1_MARK;jA++) //将最大值与最小值存入maxA、minA
{
if(maxA<=DATA_BUFF1[jA]) maxA = DATA_BUFF1[jA];
if(maxA>=DATA_BUFF1[jA]) maxA = DATA_BUFF1[jA];
}
for(jA=0;jA<ADC_LOOP1_MARK;jA++) //除去最大与最小值的相加
{
if((DATA_BUFF1[jA] != maxA) && (DATA_BUFF1[jA] != minA))
{
avg+=DATA_BUFF1[jA];
}
if(DATA_BUFF1[jA] == maxA) maxA=0xffff;
if(DATA_BUFF1[jA] == minA) maxA=0xffff;
}
minA = avg/(ADC_LOOP1_MARK-1); //求取平均数
return minA;
}
//[第二级adc滤波]读10次一级滤波后的数据，只有10次都相同才返回最終ADC数据值
uint16_t adc_getavg2(uint16_t adc)
{
uint8_t jA;
uint8_t cou=0;
for(jA=0;jA<(ADC_LOOP2_MARK-1);jA++)
{
DATA_BUFF2[(ADC_LOOP2_MARK-1)-jA] = DATA_BUFF2[(ADC_LOOP2_MARK-2)-jA];
}
DATA_BUFF2[0] = adc; //存新数据
for(jA=0;jA<(ADC_LOOP2_MARK-2);jA++)
{
if(DATA_BUFF2[jA] == adc)
{
cou++;
if(cou >= ADC_LOOP2_MARK-2)
{
DATA_BUFF2[ADC_LOOP2_MARK-1] = adc;
}
}else{
cou = 0;
}
}
return DATA_BUFF2[ADC_LOOP2_MARK-1];
}
#include "debug.h"
float ntc_temp(uint16_t adc , uint8_t *ntc_state)
{
float gather_now_voltage=0;
float ntc_now_resistance=0;
int index=0;
if(adc <= SHORT_CIRCUIT_THRESHOLD) //小于15为短路
{
*ntc_state = 1;
}
else if(adc >= OPEN_CIRCUIT_THRESHOLD) //大于4080等于开路
{
*ntc_state = 2;
}else{
*ntc_state = 0;
}
/*采集得到Va点电压 Va=gather_now_voltage*/
gather_now_voltage=adc * ADC_REFERENCE_VOLTAGE/4096;
if(gather_now_voltage==0)
{
gather_now_voltage=0.01;
}
/*求出热敏电阻的阻值 我这里Vcc电压和adc基准电压相等 r2=10k=10000*/
ntc_now_resistance=gather_now_voltage/((ADC_REFERENCE_VOLTAGE-gather_now_voltage)/10000);/*r=u/i*/
/*根据热敏电阻阻值查表得出温度*/
for(index=0; index<NTC_LIST_MAX_SIZE; index++)
{
if(ntc_10k_table[index].resistance >= ntc_now_resistance)/*查到该温度表索引为 index*/
{
float min_resistance = (float)ntc_10k_table[(index>0) ? index-1 : 0].resistance;/*得出下区间电阻值*/
float max_resistance = (float)ntc_10k_table[index].resistance;/*得出上区间电阻值*/
float d1 = (float)(max_resistance - min_resistance) / 10;/*将该区间的阻值分为10等分*/
float d2 = (float)(((ntc_now_resistance - min_resistance) / d1));/*得出n份*0.1°C*/
d2 = (10 - d2);
/*以上四步是求小数点温度*/
return (float)(ntc_10k_table[index].temperature*10) + d2;
}
}
return (0.0);
}
ntc_3950.h
#ifndef __NTC_3950_H
#define __NTC_3950_H
#include "stm32f0xx_hal.h"
#include "main.h"
#define ADC_LOOP1_MARK 20
#define ADC_LOOP2_MARK 5
/*定义一个结构体：温度，电阻阻值*/
typedef struct{
int temperature;//单位：°C
float resistance;//单位：Ω
}NTC_10KTYPE;
#define NTC_LIST_MAX_SIZE (sizeof(ntc_10k_table) / sizeof(ntc_10k_table[0]))/*表的长度*/
#define ADC_REFERENCE_VOLTAGE (float)3300 /*adc 电压基准*/
extern ADC_HandleTypeDef hadc;
extern uint16_t DATA_BUFF1[ADC_LOOP1_MARK];
extern uint16_t DATA_BUFF2[ADC_LOOP2_MARK];
uint16_t NTC_ADC(void);
uint16_t adc_getavg1(uint16_t adc);
uint16_t adc_getavg2(uint16_t adc);
float ntc_temp(uint16_t adc , uint8_t *ntc_state);
#endif
在main.c的使用如下：
static float temp_data=0.0;
temp_data = ntc_temp(adc_getavg2(adc_getavg1(NTC_ADC())),&ntc_state);
Info.temp = temp_data; //进行整数转化
switch (ntc_state)
{
case 0: //NTC正常工作
if(Info.temp >= 0) //单位确认
{
Info.temp_unit = 0; //负号关闭
}else if(Info.temp < 0){
Info.temp_unit = 1; //负号开启
Info.temp = abs(Info.temp); //转换为正数
}
break;
case 1: //NTC短路
break;
case 2: //NTC开路
break;
default:
break;
}最终采集温度比较理想，这章主要就贴了个代码，主要是有点难受不想写了，后面在补充吧