Test DHT22 Sensors with Arduino and MATLAB

This project shows how to use MATLAB and Arduino to acquire and fix data from a bundle of DHT22 sensors, live plot, and export the results.

Sep 5, 2018

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15906 views

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10 respects

environmental sensing

data collection

Components and supplies

Capacitor 10 µF

Jumper wires (generic)

Pushbutton switch 12mm

Resistor 1k ohm

Resistor 10k ohm

Breadboard (generic)

Arduino UNO

DHT22 Temperature Sensor

Apps and platforms

Arduino IDE

MATLAB

Project description

Code

humCorr.m

matlab

MATLAB function used to correct the humidity readings from the value of one sensor. Not called if lines 66-68 of the main script DHT22_5sensor.m are commented. Ignore or edit this function according to your needs.

1function corrFact = humCorr(rh5,sensNum)
2% Humidity correction factor  from measurement of sensors 1,2,3,4,5
3% rh5 is the relative humidity of sensor  number 5
4% sensNum is the sensor number (1 to 5)
5%
6% Data to interpolate:
7%  RH5 30.843        1.008   1.007   1.065   1.011   1.000
8% RH5 53.775		1.077	1.150	1.136	1.059   1.000
9
10data = [ 36.992     1.033	1.056	1.114	1.040   1.000;...
11         62.333		1.060	1.115	1.170	1.066   1.000];
12     
13% check on input
14if sensNum ~= 1 && sensNum ~= 2 && sensNum  ~= 3 && sensNum ~= 4 && sensNum ~= 5
15    error('sensNum must be 1 or 2 or 3 or  4 or 5')
16end
17     
18deltaX = data(2,1) - data(1,1);             % scalar
19deltaY  = data(2,2:end) - data(1,2:end);     % array 1D
20m = deltaY/deltaX;                    %  slope of the linear interpolant
21
22corrFact = data(1,sensNum+1) + m(sensNum)  * (rh5 - data(1,1));
23

function corrFact = humCorr(rh5,sensNum)
% Humidity correction factor  from measurement of sensors 1,2,3,4,5
% rh5 is the relative humidity of sensor  number 5
% sensNum is the sensor number (1 to 5)
%
% Data to interpolate:
%  RH5 30.843        1.008   1.007   1.065   1.011   1.000
% RH5 53.775		1.077	1.150	1.136	1.059   1.000

data = [ 36.992     1.033	1.056	1.114	1.040   1.000;...
         62.333		1.060	1.115	1.170	1.066   1.000];
     
% check on input
if sensNum ~= 1 && sensNum ~= 2 && sensNum  ~= 3 && sensNum ~= 4 && sensNum ~= 5
    error('sensNum must be 1 or 2 or 3 or  4 or 5')
end
     
deltaX = data(2,1) - data(1,1);             % scalar
deltaY  = data(2,2:end) - data(1,2:end);     % array 1D
m = deltaY/deltaX;                    %  slope of the linear interpolant

corrFact = data(1,sensNum+1) + m(sensNum)  * (rh5 - data(1,1));

DHT22_5sensor.ino

arduino

Arduino sketch to read sensors data and pass them to the computer by the serial port.

1// Libraries
2#include <DHT.h>
3
4
5// Initialize DHT sensor for  normal 16mhz Arduino
6DHT dht1(2, DHT22);
7DHT dht2(4, DHT22);
8DHT dht3(7,  DHT22);
9DHT dht4(8, DHT22);
10DHT dht5(12, DHT22);
11
12int const stopPin  = 6;
13int stopFlag = 0;
14
15
16// Variables
17float hum;  //Stores humidity  value
18float temp; //Stores temperature value
19
20void setup()
21{
22  pinMode(stopPin,  INPUT);
23  Serial.begin(9600);
24  dht1.begin();
25  dht2.begin();
26  dht3.begin();
27  dht4.begin();
28  dht5.begin();
29}
30
31void loop()
32{
33    delay(2000);
34
35    // Read humidity from the 5 sensors and display it on a single line
36    hum  = dht1.readHumidity();
37    Serial.print(hum);
38    Serial.print(":");
39    hum = dht2.readHumidity();
40    Serial.print(hum);
41    Serial.print(":");
42    hum = dht3.readHumidity();
43    Serial.print(hum);
44    Serial.print(":");
45    hum = dht4.readHumidity();
46    Serial.print(hum);
47    Serial.print(":");
48    hum = dht5.readHumidity();
49    Serial.print(hum);
50    Serial.print(":");
51
52    // Read temperature from the 5 sensors and display it on a single line
53    temp  = dht1.readTemperature();
54    Serial.print(temp);
55    Serial.print(":");
56    temp = dht2.readTemperature();
57    Serial.print(temp);
58    Serial.print(":");
59    temp = dht3.readTemperature();
60    Serial.print(temp);
61    Serial.print(":");
62    temp = dht4.readTemperature();
63    Serial.print(temp);
64    Serial.print(":");
65    temp = dht5.readTemperature();
66
67    // Check stop condition
68    stopFlag  = digitalRead(stopPin);
69      if (stopFlag == LOW){
70        Serial.println(temp);
71      }
72      else{
73        Serial.print(temp);
74        Serial.println(":999");
75      }
76    
77}
78

// Libraries
#include <DHT.h>


// Initialize DHT sensor for  normal 16mhz Arduino
DHT dht1(2, DHT22);
DHT dht2(4, DHT22);
DHT dht3(7,  DHT22);
DHT dht4(8, DHT22);
DHT dht5(12, DHT22);

int const stopPin  = 6;
int stopFlag = 0;


// Variables
float hum;  //Stores humidity  value
float temp; //Stores temperature value

void setup()
{
  pinMode(stopPin,  INPUT);
  Serial.begin(9600);
  dht1.begin();
  dht2.begin();
  dht3.begin();
  dht4.begin();
  dht5.begin();
}

void loop()
{
    delay(2000);

    // Read humidity from the 5 sensors and display it on a single line
    hum  = dht1.readHumidity();
    Serial.print(hum);
    Serial.print(":");
    hum = dht2.readHumidity();
    Serial.print(hum);
    Serial.print(":");
    hum = dht3.readHumidity();
    Serial.print(hum);
    Serial.print(":");
    hum = dht4.readHumidity();
    Serial.print(hum);
    Serial.print(":");
    hum = dht5.readHumidity();
    Serial.print(hum);
    Serial.print(":");

    // Read temperature from the 5 sensors and display it on a single line
    temp  = dht1.readTemperature();
    Serial.print(temp);
    Serial.print(":");
    temp = dht2.readTemperature();
    Serial.print(temp);
    Serial.print(":");
    temp = dht3.readTemperature();
    Serial.print(temp);
    Serial.print(":");
    temp = dht4.readTemperature();
    Serial.print(temp);
    Serial.print(":");
    temp = dht5.readTemperature();

    // Check stop condition
    stopFlag  = digitalRead(stopPin);
      if (stopFlag == LOW){
        Serial.println(temp);
      }
      else{
        Serial.print(temp);
        Serial.println(":999");
      }
    
}

humCorr.m

matlab

1function corrFact = humCorr(rh5,sensNum)
2% Humidity correction factor   from measurement of sensors 1,2,3,4,5
3% rh5 is the relative humidity of sensor   number 5
4% sensNum is the sensor number (1 to 5)
5%
6% Data to interpolate:
7%   RH5 30.843        1.008   1.007   1.065   1.011   1.000
8% RH5 53.775		1.077	1.150	1.136	1.059    1.000
9
10data = [ 36.992     1.033	1.056	1.114	1.040   1.000;...
11         62.333		1.060	1.115	1.170	1.066    1.000];
12     
13% check on input
14if sensNum ~= 1 && sensNum ~= 2 && sensNum   ~= 3 && sensNum ~= 4 && sensNum ~= 5
15    error('sensNum must be 1 or 2 or 3 or   4 or 5')
16end
17     
18deltaX = data(2,1) - data(1,1);             % scalar
19deltaY   = data(2,2:end) - data(1,2:end);     % array 1D
20m = deltaY/deltaX;                    %   slope of the linear interpolant
21
22corrFact = data(1,sensNum+1) + m(sensNum)   * (rh5 - data(1,1));
23

function corrFact = humCorr(rh5,sensNum)
% Humidity correction factor   from measurement of sensors 1,2,3,4,5
% rh5 is the relative humidity of sensor   number 5
% sensNum is the sensor number (1 to 5)
%
% Data to interpolate:
%   RH5 30.843        1.008   1.007   1.065   1.011   1.000
% RH5 53.775		1.077	1.150	1.136	1.059    1.000

data = [ 36.992     1.033	1.056	1.114	1.040   1.000;...
         62.333		1.060	1.115	1.170	1.066    1.000];
     
% check on input
if sensNum ~= 1 && sensNum ~= 2 && sensNum   ~= 3 && sensNum ~= 4 && sensNum ~= 5
    error('sensNum must be 1 or 2 or 3 or   4 or 5')
end
     
deltaX = data(2,1) - data(1,1);             % scalar
deltaY   = data(2,2:end) - data(1,2:end);     % array 1D
m = deltaY/deltaX;                    %   slope of the linear interpolant

corrFact = data(1,sensNum+1) + m(sensNum)   * (rh5 - data(1,1));

DHT22_5sensor.ino

arduino

Arduino sketch to read sensors data and pass them to the computer by the serial port.

1// Libraries
2#include <DHT.h>
3
4
5// Initialize DHT sensor for
6  normal 16mhz Arduino
7DHT dht1(2, DHT22);
8DHT dht2(4, DHT22);
9DHT dht3(7,
10  DHT22);
11DHT dht4(8, DHT22);
12DHT dht5(12, DHT22);
13
14int const stopPin
15  = 6;
16int stopFlag = 0;
17
18
19// Variables
20float hum;  //Stores humidity
21  value
22float temp; //Stores temperature value
23
24void setup()
25{
26  pinMode(stopPin,
27  INPUT);
28  Serial.begin(9600);
29  dht1.begin();
30  dht2.begin();
31  dht3.begin();
32
33  dht4.begin();
34  dht5.begin();
35}
36
37void loop()
38{
39    delay(2000);
40
41
42    // Read humidity from the 5 sensors and display it on a single line
43    hum
44  = dht1.readHumidity();
45    Serial.print(hum);
46    Serial.print(":");
47
48    hum = dht2.readHumidity();
49    Serial.print(hum);
50    Serial.print(":");
51
52    hum = dht3.readHumidity();
53    Serial.print(hum);
54    Serial.print(":");
55
56    hum = dht4.readHumidity();
57    Serial.print(hum);
58    Serial.print(":");
59
60    hum = dht5.readHumidity();
61    Serial.print(hum);
62    Serial.print(":");
63
64
65    // Read temperature from the 5 sensors and display it on a single line
66    temp
67  = dht1.readTemperature();
68    Serial.print(temp);
69    Serial.print(":");
70
71    temp = dht2.readTemperature();
72    Serial.print(temp);
73    Serial.print(":");
74
75    temp = dht3.readTemperature();
76    Serial.print(temp);
77    Serial.print(":");
78
79    temp = dht4.readTemperature();
80    Serial.print(temp);
81    Serial.print(":");
82
83    temp = dht5.readTemperature();
84
85    // Check stop condition
86    stopFlag
87  = digitalRead(stopPin);
88      if (stopFlag == LOW){
89        Serial.println(temp);
90
91      }
92      else{
93        Serial.print(temp);
94        Serial.println(":999");
95
96      }
97    
98}
99

// Libraries
#include <DHT.h>


// Initialize DHT sensor for
  normal 16mhz Arduino
DHT dht1(2, DHT22);
DHT dht2(4, DHT22);
DHT dht3(7,
  DHT22);
DHT dht4(8, DHT22);
DHT dht5(12, DHT22);

int const stopPin
  = 6;
int stopFlag = 0;


// Variables
float hum;  //Stores humidity
  value
float temp; //Stores temperature value

void setup()
{
  pinMode(stopPin,
  INPUT);
  Serial.begin(9600);
  dht1.begin();
  dht2.begin();
  dht3.begin();

  dht4.begin();
  dht5.begin();
}

void loop()
{
    delay(2000);


    // Read humidity from the 5 sensors and display it on a single line
    hum
  = dht1.readHumidity();
    Serial.print(hum);
    Serial.print(":");

    hum = dht2.readHumidity();
    Serial.print(hum);
    Serial.print(":");

    hum = dht3.readHumidity();
    Serial.print(hum);
    Serial.print(":");

    hum = dht4.readHumidity();
    Serial.print(hum);
    Serial.print(":");

    hum = dht5.readHumidity();
    Serial.print(hum);
    Serial.print(":");


    // Read temperature from the 5 sensors and display it on a single line
    temp
  = dht1.readTemperature();
    Serial.print(temp);
    Serial.print(":");

    temp = dht2.readTemperature();
    Serial.print(temp);
    Serial.print(":");

    temp = dht3.readTemperature();
    Serial.print(temp);
    Serial.print(":");

    temp = dht4.readTemperature();
    Serial.print(temp);
    Serial.print(":");

    temp = dht5.readTemperature();

    // Check stop condition
    stopFlag
  = digitalRead(stopPin);
      if (stopFlag == LOW){
        Serial.println(temp);

      }
      else{
        Serial.print(temp);
        Serial.println(":999");

      }
    
}

DHT22_5sensor.m

matlab

MATLAB code to read serial data from the Arduino. Please check your port number on line 18. First acquisition should be without correction. For the first time leave lines 66 to 68 commented. I have used an external tool to verify temperature and humidity readings and it appeared that sensor number 5 read both correctly in several condition. I have written the humCorr.m function to fix the other sensors readings from the value of sensor number 5. If interested in correction, manipulate humCorr.m function and/or lines 66-68 according to your needs.

1% Script to test a bundle of 5 DHT22 sensors with an Arduino (Uno)
2%  microcontroller. Acquire data from the sensors until a stop button is
3% pressed  on the board or a time limit is reached. Plot last 10 minutes of
4% live data  during acquisition, the entire data set after the acquisition,
5% and save these  data on a spreadsheet.
6
7close all
8instrreset
9clear
10clc
11
12% Acquisition  time (min). Insert inf to disable time limit.
13waitTime = 10;
14
15%% Acquire  and display live data
16
17% Open serial communication
18s = serial('/dev/cu.usbmodem411','BAUD',9600);
19
20figure
21color  = ['b', 'r', 'g', 'm', 'c', 'b', 'r', 'g', 'm', 'c'];
22for i = 1:5
23    h(i)  = animatedline('Color',color(i),'LineWidth',2);
24end
25axh = gca;
26axh.YGrid  = 'on';
27axh.YLim = [30 80];
28xlabel('Time')
29ylabel('Humidity (%)')
30legend('Sensor  1', 'Sensor 2', 'Sensor 3', 'Sensor 4', 'Sensor 5',...
31    'Location','NorthWest')
32
33figure
34for  i = 6:10
35    h(i) = animatedline('Color',color(i),'LineWidth',2);
36end
37axt  = gca;
38axt.YGrid = 'on';
39axt.YLim = [10 40];
40xlabel('Time')
41ylabel('Temperature  (\\circC)')
42legend('Sensor 1', 'Sensor 2', 'Sensor 3', 'Sensor 4', 'Sensor 5',...
43    'Location','NorthWest')
44
45stop = false;
46waitTime = duration(0,waitTime,0);
47startTime  = datetime('now');
48t = datetime('now') - startTime;
49
50while ~stop && t <  waitTime
51    
52    % Read data from serial port
53    fopen(s);
54    idn  = fscanf(s);
55    fclose(s);
56    
57    % Separate data
58    C = strsplit(idn,':');
59    
60    % Display data in MATLAB command window
61    serialData = str2double(C);
62    
63    % Humidity correction factor from measurement of sensor 5
64    corrData  = serialData;
65    % First acquisition should be without correction. For the first  time leave lines 66 to 68 commented. I have used an external tool to verify temperature  and humidity readings and it appeared that sensor number 5 read both correctly in  several condition. I have written the humCorr.m function to fix the other sensors  readings from the value of sensor 5. If interested in correction, manipulate humCorr.m  function and/or the following lines according to your needs.
66    %for i = 1:4
67    %   corrData(i) = serialData(i) * humCorr(serialData(5),i);
68    %end
69    
70    disp(corrData)
71    
72    % Get current time
73    t = datetime('now')  - startTime;
74       
75    % Add points to animation (humidity data)
76    for  i = 1:5
77        addpoints(h(i),datenum(t),corrData(i))
78    end
79    
80    % Update axes
81    axh.XLim = datenum([t-seconds(600) t]);
82    datetick('x','keeplimits')
83    drawnow
84    
85    % Add points to animation (temperature data)
86    for  i = 6:10
87        addpoints(h(i),datenum(t),corrData(i))
88    end
89    
90    % Update axes
91    axt.XLim = datenum([t-seconds(600) t]);
92    datetick('x','keeplimits')
93    drawnow
94    
95    % Check stop condition from serial monitor
96    if  str2double(C{end}) == 999
97        stop = true;
98    end
99end
100
101% Output  message
102if stop
103    disp('Data acquisition ended because the STOP button has  been pressed')
104else
105    disp('Data acquisition ended because the TIME limit  has been reached')
106end
107
108%% Plot the recorded data
109
110for i = 1:5
111    [~,humLogs(i,:)] = getpoints(h(i));
112    [timeLogs,tempLogs(i,:)] = getpoints(h(i+5));
113end
114timeSecs  = (timeLogs-timeLogs(1))*24*3600;
115
116figure
117subplot(1,2,1)
118plot(timeSecs,humLogs,'LineWidth',2)
119grid  on
120ax = gca;
121ylim([round(ax.YLim(1)-2), round(ax.YLim(2)+2)])
122xlabel('Elapsed  time (s)')
123ylabel('Humidity (%)')
124
125subplot(1,2,2)
126timeSecs = (timeLogs-timeLogs(1))*24*3600;
127plot(timeSecs,tempLogs,'LineWidth',2)
128hold  off, grid on
129ax = gca;
130ylim([round(ax.YLim(1)-2), round(ax.YLim(2)+2)])
131xlabel('Elapsed  time (s)')
132ylabel('Temperature (\\circC)')
133legend('Sensor 1', 'Sensor 2',  'Sensor 3', 'Sensor 4', 'Sensor 5',...
134    'Location','Best')
135
136%% Save  results to a file
137
138T = table(timeSecs',humLogs',tempLogs','VariableNames',...
139    {'Time_s','Relative_Humidity','Temperature_C'});
140filename = 'Humidity_and_Temperature_Data.xls';
141
142%  Delete previous file, if exists, to avoid append of data
143if exist(filename,'file')
144    delete(filename)
145end
146
147% Write table to file
148writetable(T,filename)
149%  Print confirmation to command line
150fprintf('Results table with %g humidity and  temperature measurements saved to file %s\
151',...
152    length(timeSecs),filename)
153
154%%  Summary charts with original data, averaged data, and uncertainty
155
156for sensor  = 1:5
157    
158    % Smooth out readings with moving average filter
159    smoothHum  = smooth(humLogs(sensor,:),25);
160    smoothTemp = smooth(tempLogs(sensor,:),25);
161    
162    % Typical accuracy of the humidity sensor
163    humMax = 1.02 * smoothHum;
164    humMin = 0.98 * smoothHum;
165    
166    % Worst accuracy of the humidity sensor
167    humMaxW = 1.05 * smoothHum;
168    humMinW = 0.95 * smoothHum;
169    
170    %  Accuracy of the temperature sensor
171    tempMax = smoothTemp + 0.5;
172    tempMin  = smoothTemp - 0.5;
173    
174    figure
175    subplot(1,2,1), hold on
176    plot(timeSecs,humLogs(sensor,:),'b','LineWidth',2)
177    plot(timeSecs,smoothHum,'r','LineWidth',1)
178    plot(timeSecs,humMin,'r--','LineWidth',2)
179    plot(timeSecs,humMax,'r--','LineWidth',2)
180    plot(timeSecs,humMinW,'m--','LineWidth',1)
181    plot(timeSecs,humMaxW,'m--','LineWidth',1)
182    hold off, grid on, ylim([round(min(humMinW))-2,  round(max(humMaxW))+2])
183    xlabel('Elapsed time (s)')
184    ylabel('Humidity  (%)')
185    title(['Humidity data, average, and uncertainty for sensor ',num2str(sensor)])
186    
187    subplot(1,2,2), hold on
188    plot(timeSecs,tempLogs(sensor,:),'b','LineWidth',2)
189    plot(timeSecs,smoothTemp,'r','LineWidth',1)
190    plot(timeSecs,tempMin,'r--','LineWidth',2)
191    plot(timeSecs,tempMax,'r--','LineWidth',2)
192    hold off, grid on, ylim([round(min(tempMin))-2,  round(max(tempMax))+2])
193    xlabel('Elapsed time (s)')
194    ylabel('Temperature  (\\circC)')
195    title(['Temperature data, average, and uncertainty for sensor  ',num2str(sensor)])
196    
197end

% Script to test a bundle of 5 DHT22 sensors with an Arduino (Uno)
%  microcontroller. Acquire data from the sensors until a stop button is
% pressed  on the board or a time limit is reached. Plot last 10 minutes of
% live data  during acquisition, the entire data set after the acquisition,
% and save these  data on a spreadsheet.

close all
instrreset
clear
clc

% Acquisition  time (min). Insert inf to disable time limit.
waitTime = 10;

%% Acquire  and display live data

% Open serial communication
s = serial('/dev/cu.usbmodem411','BAUD',9600);

figure
color  = ['b', 'r', 'g', 'm', 'c', 'b', 'r', 'g', 'm', 'c'];
for i = 1:5
    h(i)  = animatedline('Color',color(i),'LineWidth',2);
end
axh = gca;
axh.YGrid  = 'on';
axh.YLim = [30 80];
xlabel('Time')
ylabel('Humidity (%)')
legend('Sensor  1', 'Sensor 2', 'Sensor 3', 'Sensor 4', 'Sensor 5',...
    'Location','NorthWest')

figure
for  i = 6:10
    h(i) = animatedline('Color',color(i),'LineWidth',2);
end
axt  = gca;
axt.YGrid = 'on';
axt.YLim = [10 40];
xlabel('Time')
ylabel('Temperature  (\\circC)')
legend('Sensor 1', 'Sensor 2', 'Sensor 3', 'Sensor 4', 'Sensor 5',...
    'Location','NorthWest')

stop = false;
waitTime = duration(0,waitTime,0);
startTime  = datetime('now');
t = datetime('now') - startTime;

while ~stop && t <  waitTime
    
    % Read data from serial port
    fopen(s);
    idn  = fscanf(s);
    fclose(s);
    
    % Separate data
    C = strsplit(idn,':');
    
    % Display data in MATLAB command window
    serialData = str2double(C);
    
    % Humidity correction factor from measurement of sensor 5
    corrData  = serialData;
    % First acquisition should be without correction. For the first  time leave lines 66 to 68 commented. I have used an external tool to verify temperature  and humidity readings and it appeared that sensor number 5 read both correctly in  several condition. I have written the humCorr.m function to fix the other sensors  readings from the value of sensor 5. If interested in correction, manipulate humCorr.m  function and/or the following lines according to your needs.
    %for i = 1:4
    %   corrData(i) = serialData(i) * humCorr(serialData(5),i);
    %end
    
    disp(corrData)
    
    % Get current time
    t = datetime('now')  - startTime;
       
    % Add points to animation (humidity data)
    for  i = 1:5
        addpoints(h(i),datenum(t),corrData(i))
    end
    
    % Update axes
    axh.XLim = datenum([t-seconds(600) t]);
    datetick('x','keeplimits')
    drawnow
    
    % Add points to animation (temperature data)
    for  i = 6:10
        addpoints(h(i),datenum(t),corrData(i))
    end
    
    % Update axes
    axt.XLim = datenum([t-seconds(600) t]);
    datetick('x','keeplimits')
    drawnow
    
    % Check stop condition from serial monitor
    if  str2double(C{end}) == 999
        stop = true;
    end
end

% Output  message
if stop
    disp('Data acquisition ended because the STOP button has  been pressed')
else
    disp('Data acquisition ended because the TIME limit  has been reached')
end

%% Plot the recorded data

for i = 1:5
    [~,humLogs(i,:)] = getpoints(h(i));
    [timeLogs,tempLogs(i,:)] = getpoints(h(i+5));
end
timeSecs  = (timeLogs-timeLogs(1))*24*3600;

figure
subplot(1,2,1)
plot(timeSecs,humLogs,'LineWidth',2)
grid  on
ax = gca;
ylim([round(ax.YLim(1)-2), round(ax.YLim(2)+2)])
xlabel('Elapsed  time (s)')
ylabel('Humidity (%)')

subplot(1,2,2)
timeSecs = (timeLogs-timeLogs(1))*24*3600;
plot(timeSecs,tempLogs,'LineWidth',2)
hold  off, grid on
ax = gca;
ylim([round(ax.YLim(1)-2), round(ax.YLim(2)+2)])
xlabel('Elapsed  time (s)')
ylabel('Temperature (\\circC)')
legend('Sensor 1', 'Sensor 2',  'Sensor 3', 'Sensor 4', 'Sensor 5',...
    'Location','Best')

%% Save  results to a file

T = table(timeSecs',humLogs',tempLogs','VariableNames',...
    {'Time_s','Relative_Humidity','Temperature_C'});
filename = 'Humidity_and_Temperature_Data.xls';

%  Delete previous file, if exists, to avoid append of data
if exist(filename,'file')
    delete(filename)
end

% Write table to file
writetable(T,filename)
%  Print confirmation to command line
fprintf('Results table with %g humidity and  temperature measurements saved to file %s\
',...
    length(timeSecs),filename)

%%  Summary charts with original data, averaged data, and uncertainty

for sensor  = 1:5
    
    % Smooth out readings with moving average filter
    smoothHum  = smooth(humLogs(sensor,:),25);
    smoothTemp = smooth(tempLogs(sensor,:),25);
    
    % Typical accuracy of the humidity sensor
    humMax = 1.02 * smoothHum;
    humMin = 0.98 * smoothHum;
    
    % Worst accuracy of the humidity sensor
    humMaxW = 1.05 * smoothHum;
    humMinW = 0.95 * smoothHum;
    
    %  Accuracy of the temperature sensor
    tempMax = smoothTemp + 0.5;
    tempMin  = smoothTemp - 0.5;
    
    figure
    subplot(1,2,1), hold on
    plot(timeSecs,humLogs(sensor,:),'b','LineWidth',2)
    plot(timeSecs,smoothHum,'r','LineWidth',1)
    plot(timeSecs,humMin,'r--','LineWidth',2)
    plot(timeSecs,humMax,'r--','LineWidth',2)
    plot(timeSecs,humMinW,'m--','LineWidth',1)
    plot(timeSecs,humMaxW,'m--','LineWidth',1)
    hold off, grid on, ylim([round(min(humMinW))-2,  round(max(humMaxW))+2])
    xlabel('Elapsed time (s)')
    ylabel('Humidity  (%)')
    title(['Humidity data, average, and uncertainty for sensor ',num2str(sensor)])
    
    subplot(1,2,2), hold on
    plot(timeSecs,tempLogs(sensor,:),'b','LineWidth',2)
    plot(timeSecs,smoothTemp,'r','LineWidth',1)
    plot(timeSecs,tempMin,'r--','LineWidth',2)
    plot(timeSecs,tempMax,'r--','LineWidth',2)
    hold off, grid on, ylim([round(min(tempMin))-2,  round(max(tempMax))+2])
    xlabel('Elapsed time (s)')
    ylabel('Temperature  (\\circC)')
    title(['Temperature data, average, and uncertainty for sensor  ',num2str(sensor)])
    
end

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