NTC热敏电阻的应用
描述
1 NTC热敏电阻
NTC热敏电阻一般用于环境温度的测量，可以识别-20到100度，如果要采集更高的温度就需要用到热电偶了。
2 NTC热敏电阻R/T对照表
T(℃) R(KΩ) T(℃) R(KΩ) T(℃) R(KΩ)
-20.0 95.3370 20.5 12.2138 61.0 2.3820
-19.5 92.6559 21.0 11.9425 61.5 2.3394
-19.0 90.0580 21.5 11.6778 62.0 2.2977
-18.5 87.5406 22.0 11.4198 62.5 2.2568
-18.0 85.1009 22.5 11.1681 63.0 2.2167
-17.5 82.7364 23.0 10.9227 63.5 2.1775
-17.0 80.4445 23.5 10.6834 64.0 2.1390
-16.5 78.2227 24.0 10.4499 64.5 2.1013
-16.0 76.0689 24.5 10.2222 65.0 2.0644
-15.5 73.9806 25.0 10.0000 65.5 2.0282
-15.0 71.9558 25.5 9.7833 66.0 1.9928
-14.5 69.9923 26.0 9.5718 66.5 1.9580
-14.0 68.0881 26.5 9.3655 67.0 1.9240
-13.5 66.2412 27.0 9.1642 67.5 1.8906
-13.0 64.4499 27.5 8.9677 68.0 1.8579
-12.5 62.7122 28.0 8.7760 68.5 1.8258
-12.0 61.0264 28.5 8.5889 69.0 1.7944
-11.5 59.3908 29.0 8.4063 69.5 1.7636
-11.0 57.8038 29.5 8.2281 70.0 1.7334
-10.5 56.2639 30.0 8.0541 70.5 1.7037
-10.0 54.7694 30.5 7.8842 71.0 1.6747
-9.5 53.3189 31.0 7.7184 71.5 1.6462
-9.0 51.9111 31.5 7.5565 72.0 1.6183
-8.5 50.5445 32.0 7.3985 72.5 1.5910
-8.0 49.2178 32.5 7.2442 73.0 1.5641
-7.5 47.9298 33.0 7.0935 73.5 1.5378
-7.0 46.6792 33.5 6.9463 74.0 1.5120
-6.5 45.4649 34.0 6.8026 74.5 1.4867
-6.0 44.2856 34.5 6.6622 75.0 1.4619
-5.5 43.1403 35.0 6.5251 75.5 1.4375
-5.0 42.0279 35.5 6.3912 76.0 1.4136
-4.5 40.9474 36.0 6.2604 76.5 1.3902
-4.0 39.8978 36.5 6.1326 77.0 1.3672
-3.5 38.8780 37.0 6.0077 77.5 1.3447
-3.0 37.8873 37.5 5.8858 78.0 1.3225
-2.5 36.9246 38.0 5.7666 78.5 1.3008
-2.0 35.9892 38.5 5.6501 79.0 1.2795
-1.5 35.0801 39.0 5.5363 79.5 1.2586
-1.0 34.1965 39.5 5.4251 80.0 1.2381
-0.5 33.3378 40.0 5.3164 80.5 1.2180
0.0 32.5030 40.5 5.2102 81.0 1.1983
0.5 31.6915 41.0 5.1064 81.5 1.1789
1.0 30.9026 41.5 5.0049 82.0 1.1599
1.5 30.1355 42.0 4.9057 82.5 1.1412
2.0 29.3896 42.5 4.8088 83.0 1.1229
2.5 28.6644 43.0 4.7140 83.5 1.1050
3.0 27.9590 43.5 4.6213 84.0 1.0873
3.5 27.2730 44.0 4.5307 84.5 1.0700
4.0 26.6058 44.5 4.4421 85.0 1.0530
4.5 25.9567 45.0 4.3554 85.5 1.0363
5.0 25.3254 45.5 4.2707 86.0 1.0199
5.5 24.7111 46.0 4.1878 86.5 1.0038
6.0 24.1135 46.5 4.1068 87.0 0.9880
6.5 23.5320 47.0 4.0275 87.5 0.9725
7.0 22.9661 47.5 3.9500 88.0 0.9573
7.5 22.4154 48.0 3.8742 88.5 0.9424
8.0 21.8795 48.5 3.8000 89.0 0.9277
8.5 21.3579 49.0 3.7275 89.5 0.9133
9.0 20.8502 49.5 3.6565 90.0 0.8991
9.5 20.3559 50.0 3.5870 90.5 0.8852
10.0 19.8747 50.5 3.5190 91.0 0.8715
10.5 19.4063 51.0 3.4525 91.5 0.8581
11.0 18.9502 51.5 3.3875 92.0 0.8450
11.5 18.5060 52.0 3.3238 92.5 0.8320
12.0 18.0735 52.5 3.2615 93.0 0.8193
12.5 17.6523 53.0 3.2005 93.5 0.8068
13.0 17.2421 53.5 3.1408 94.0 0.7945
13.5 16.8426 54.0 3.0824 94.5 0.7825
14.0 16.4534 54.5 3.0252 95.0 0.7707
14.5 16.0743 55.0 2.9692 95.5 0.7590
15.0 15.7049 55.5 2.9144 96.0 0.7476
15.5 15.3450 56.0 2.8608 96.5 0.7364
16.0 14.9944 56.5 2.8082 97.0 0.7253
16.5 14.6528 57.0 2.7568 97.5 0.7145
17.0 14.3198 57.5 2.7065 98.0 0.7038
17.5 13.9954 58.0 2.6572 98.5 0.6933
18.0 13.6792 58.5 2.6089 99.0 0.6831
18.5 13.3710 59.0 2.5616 99.5 0.6729
19.0 13.0705 59.5 2.5153 100.0 0.6630
19.5 12.7777 60.0 2.4700
20.0 12.4922 60.5 2.4255
3 分压公式
根据欧姆定律，电流I=U/R
可以求出I=(U总-U2)/R1
同样I=(U总/R1+R2)那么U2=(U总/R1+R2)*R2
同样R2=(U2*R1)/(U总-U2)以-15度为例，阻值是71.9558K，
那么电压U2=(U总/R1+R2)*R2
U2=(U总*71.9558)/(10+71.9558)
假设U总为3.3V，那么U2=2.89V，12位ADC对应的值是3595
4.1 快速生成温度表
4.1.1 利用excel将电阻阻值保存为.csv格式的文件
-复制所有NTC电阻阻值
-再新建一个test.csv文件，在第一行第一列选择性粘贴，粘贴内容转置
- 利用记事本打开test.csv，将电阻阻值复制粘贴到数组中。
以下是完整代码
#include
#include
#include "stdint.h"
#define LENGTH_OF_ARRAY(A) sizeof(A)/sizeof(A[0])
#define CONFIG_MIN_TEMP -15
#define CONFIG_MAX_TEMP 80
#define CONFIG_CNT_PRINTF_LNIE 5
FILE *fp = 0;
float res_values[] =
{
71.9558,68.0881,64.4499,61.0264,57.8038,54.7694,51.9111,49.2178,46.6792,44.2856,42.0279,39.8978,37.8873,35.9892,34.1965,32.503,30.9026,29.3896,27.959,26.6058,25.3254,24.1135,22.9661,21.8795,20.8502,19.8747,18.9502,18.0735,17.2421,16.4534,15.7049,14.9944,14.3198,13.6792,13.0705,12.4922,11.9425,11.4198,10.9227,10.4499,10,9.5718,9.1642,8.776,8.4063,8.0541,7.7184,7.3985,7.0935,6.8026,6.5251,6.2604,6.0077,5.7666,5.5363,5.3164,5.1064,4.8088,4.714,4.5307,4.3554,4.1878,4.0275,3.8742,3.7275,3.587,3.4525,3.3238,3.2005,3.0824,2.9692,2.8608,2.7568,2.6572,2.5616,2.47,2.382,2.2977,2.2167,2.139,2.0644,1.9928,1.924,1.8579,1.7944,1.7334,1.6747,1.6183,1.5641,
1.512,1.4619,1.4136,1.3672,1.3225,1.2795,1.2381
};
static int8_t res_to_voltage(int16_t start_temperature,float vol_ref,float vol_total,float res_pull,uint16_t adc_max)
{
uint16_t get_cnt = LENGTH_OF_ARRAY(res_values);
if ((start_temperature
这样就生成了一个温度值对应的ADC数组，可以粘贴到应用程序中。
/*基准电压:3.300000V 总电压:3.30V 上拉电阻10.000000K ADC最大值4095*/
const uint16_t ntc_adc[]={
3595,3570,3544,3518,3491,
/*-15 -14 -13 -12 -11 */
3462,3433,3403,3372,3340,
/*-10 -9 -8 -7 -6 */
3307,3274,3239,3204,3168,
/*-5 -4 -3 -2 -1 */
3131,3093,3055,3016,2976,
/*0 1 2 3 4 */
2935,2894,2852,2810,2767,
/*5 6 7 8 9 */
2724,2680,2636,2591,2546,
/*10 11 12 13 14 */
2501,2456,2411,2365,2320,
/*15 16 17 18 19 */
2274,2228,2183,2137,2092,
/*20 21 22 23 24 */
2047,2002,1958,1914,1870,
/*25 26 27 28 29 */
1826,1783,1741,1699,1657,
/*30 31 32 33 34 */
1616,1576,1536,1497,1459,
/*35 36 37 38 39 */
1421,1384,1329,1311,1276,
/*40 41 42 43 44 */
1242,1208,1175,1143,1111,
/*45 46 47 48 49 */
1081,1050,1021,992,964,
/*50 51 52 53 54 */
937,910,884,859,835,
/*55 56 57 58 59 */
811,787,765,743,721,
/*60 61 62 63 64 */
700,680,660,641,623,
/*65 66 67 68 69 */
604,587,570,553,537,
/*70 71 72 73 74 */
522,507,492,478,464,
/*75 76 77 78 79 */
451,/*80 */
};
4.2 实际应用
int8_t get_temp(uint16_t adc_val)
{
const uint16_t* buff = ntc_adc;
int8_t low = 0;
int8_t mid = 0;
int8_t high = LENGTH_OF_ARRAY(ntc_adc) - 1;
while (low <= high)
{
mid = (high + low) >> 1;
if (buff[mid] < adc_val)
{
high = mid - 1;
}
else if (buff[mid] > adc_val)
{
low = mid + 1;
}
else
{
break;
}
}
return mid - 15;
}
5 获取资源
在本公众号回复关键字”NTC”获取相关资源
6 总结
如果AD值不稳定，可以在硬件上加入Π型滤波器和电压跟随器，在软件上加入卡尔曼滤波算法，如果做一个工具可以提高做事效率，那么就值得花一些时间去做，不是为别人，只是为了节省自己的时间，时间就是我们的生命。
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