NTC 查表和公式

查表法

 

/** ************************************************************Author:Liming***
  * @brief  NTC阻值表
  * @param  float型电阻值
  * @retval None
*****************************************************************0X49E7FC7B****/
//NTC R25=10K 1% B25/50=3950K 1%
#define NTC_TAB_SIZE  181
code float NTC_TAB[NTC_TAB_SIZE]={
739.500, 705.664, 669.165, 631.466, 593.686, 556.644, 520.911, 486.858, 454.704, 424.553,//0-9 -55 to -46
396.426, 370.283, 346.049, 323.623, 302.890, 283.730, 266.022, 249.649, 234.498, 220.466,//10-19 -45 to -36
207.454, 195.372, 184.139, 173.681, 163.931, 154.827, 146.315, 138.347, 130.877, 123.866,//20-29 -35 to -26
117.280, 111.084, 105.252,  99.756,  94.573,  89.682,  85.063,  80.699,  76.574,  72.672,//30-39 -25 to -16
68.982, 65.489, 62.183, 59.052, 56.087, 53.280, 50.620, 48.100, 45.712, 43.450,//40-49 -15 to -6
41.306, 39.274, 37.349, 35.524, 33.795, 32.116, 30.601, 29.128, 27.732, 26.408,//50-59 -5 to  4
25.152, 23.962, 22.833, 21.762, 20.746, 19.783, 18.868, 18.000, 17.177, 16.395,//60-69 5 to 14
15.652, 14.947, 14.277, 13.641, 13.036, 12.461, 11.915, 11.395, 10.901, 10.431,//70-79 15 to 24
10.000,  9.557,  9.151,  8.765,  8.397,  8.047,  7.712,  7.394,  7.090,  6.800,//80-89 25 to 34
6.523, 6.259, 6.008, 5.767, 5.537, 5.318, 5.108, 4.907, 4.716, 4.532,//90-99 35 to 44
4.357, 4.189, 4.029, 3.875, 3.728, 3.588, 3.453, 3.324, 3.200, 3.081,//00-09 45 to 54
2.968, 2.859, 2.754, 2.654, 2.558, 2.466, 2.377, 2.293, 2.211, 2.133,//10-19 55 to 64
2.058, 1.986, 1.917, 1.850, 1.786, 1.725, 1.666, 1.610, 1.555, 1.503,//20-29 65 to 74
1.452, 1.404, 1.358, 1.313, 1.270, 1.228, 1.189, 1.150, 1.113, 1.078,//30-39 75 to 84
1.044, 1.011, 0.979, 0.948, 0.919, 0.890, 0.863, 0.837, 0.811, 0.787,//40-49 85 to 94
0.763, 0.740, 0.718, 0.697, 0.676, 0.657, 0.637, 0.619, 0.601, 0.584,//50-59 95 to 104
0.567, 0.551, 0.535, 0.520, 0.505, 0.491, 0.478, 0.464, 0.451, 0.439,//60-69 105 to 114
0.427, 0.415, 0.404, 0.393, 0.382, 0.371, 0.361, 0.351, 0.342, 0.333,//70-79 115 to 124
0.324
};

 

/** ************************************************************Author:Liming***
  * @brief  根据NTC阻值查表计算当前温度
            STC8G2K 24M 约 140us
  * @param  Rntc float型电阻值
  * @retval None
*****************************************************************0X49E7FC7B****/
char Calculate_Temperature(float Rntc)
{
  uint8_t st,ed,m;
  uint8_t i;
  st = 0;
  ed = NTC_TAB_SIZE-1;
  i = 0;
//2分法查表，表中数据阻值从大到小
  if (Rntc >= NTC_TAB[st])return st;
  else if(Rntc <= NTC_TAB[ed]) return ed;

  while (st < ed)
  {
    m = (st+ed)/2;
    if (Rntc == NTC_TAB[m])break;
    if ((Rntc < NTC_TAB[m])&&(Rntc>NTC_TAB[m+1]))break;

    if (Rntc > NTC_TAB[m]) ed = m;
    else st = m;

    if (i++ >= 181) break;
  }
  if (st>ed) return 0;
return (m-55);
}

 

 

公式法

/** ************************************************************Author:Liming***
  * @brief  根据NTC阻值计算当前温度，因为使用了log所以需要包含头文件math.h
  STC8G2K 24M 约500us
  * @param  Rntc float型的电阻值
  * @retval None
*****************************************************************0X49E7FC7B****/
float BSP_ADC_GetTemperature(float Rntc)
{
	float N1,N2,N3,N4;
	float BX = 3950;//NTC B值
	float T25 = 298.15;//额定温度 绝对温度+常温273.15+25
	float R25 = 10;//
	N1 = (log(Rntc)-log(R25))/BX;
	N2 = 1/T25 + N1;
	N3 = 1/N2;
	N4 = N3-273.15;
	return N4;
}