DH11数字温湿度传感器

DH11数字温湿度传感器是一种集温度、湿度一体的复合传感器，它能把温度和湿度物理量通过温、湿度敏感元件和相应电路转化成方便计算机、PLC、智能仪表等数据采集设备直接读取的数字量。DHT11由电阻式感湿器件和NTC系数感温器件构成，具有校准数字信号输出功能，采用单总线串行接口，输出数据一共5个字节，分别表示：湿度整数位、湿度小数位，温度整数位、温度小数位及校验和，其中检验和为湿度与温度之和的最低八位数据。

 1 double Fahrenheit(double celsius)
 2 {
 3         return 1.8 * celsius + 32;
 4 }    //摄氏温度度转化为华氏温度
 5
 6 double Kelvin(double celsius)
 7 {
 8         return celsius + 273.15;
 9 }     //摄氏温度转化为开氏温度
10
11 // 露点（点在此温度时，空气饱和并产生露珠）
12 // 参考: http://wahiduddin.net/calc/density_algorithms.htm
13 double dewPoint(double celsius, double humidity)
14 {
15         double A0= 373.15/(273.15 + celsius);
16         double SUM = -7.90298 * (A0-1);
17         SUM += 5.02808 * log10(A0);
18         SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
19         SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
20         SUM += log10(1013.246);
21         double VP = pow(10, SUM-3) * humidity;
22         double T = log(VP/0.61078);   // temp var
23         return (241.88 * T) / (17.558-T);
24 }
25
26 // 快速计算露点，速度是5倍dewPoint()
27 // 参考: http://en.wikipedia.org/wiki/Dew_point
28 double dewPointFast(double celsius, double humidity)
29 {
30         double a = 17.271;
31         double b = 237.7;
32         double temp = (a * celsius) / (b + celsius) + log(humidity/100);
33         double Td = (b * temp) / (a - temp);
34         return Td;
35 }
36
37 #include <dht11.h>
38
39 dht11 DHT11;
40
41 #define DHT11PIN 2
42
43 void setup()
44 {
45   Serial.begin(9600);
46   Serial.println("DHT11 TEST PROGRAM ");
47   Serial.print("LIBRARY VERSION: ");
48   Serial.println(DHT11LIB_VERSION);
49   Serial.println();
50 }
51
52 void loop()
53 {
54   Serial.println("\n");
55
56   int chk = DHT11.read(DHT11PIN);
57
58   Serial.print("Read sensor: ");
59   switch (chk)
60   {
61     case DHTLIB_OK:
62                 Serial.println("OK");
63                 break;
64     case DHTLIB_ERROR_CHECKSUM:
65                 Serial.println("Checksum error");
66                 break;
67     case DHTLIB_ERROR_TIMEOUT:
68                 Serial.println("Time out error");
69                 break;
70     default:
71                 Serial.println("Unknown error");
72                 break;
73   }
74
75   Serial.print("Humidity (%): ");
76   Serial.println((float)DHT11.humidity, 2);
77
78   Serial.print("Temperature (oC): ");
79   Serial.println((float)DHT11.temperature, 2);
80
81   Serial.print("Temperature (oF): ");
82   Serial.println(Fahrenheit(DHT11.temperature), 2);
83
84   Serial.print("Temperature (K): ");
85   Serial.println(Kelvin(DHT11.temperature), 2);
86
87   Serial.print("Dew Point (oC): ");
88   Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));
89
90   Serial.print("Dew PointFast (oC): ");
91   Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));
92
93   delay(2000);
94 }