There are two ways t o measure physical distance.
Analog : reuler
Digtal : Untra sensor (HCSR-04)
Digital is very convenient. Measure using ultra sensor.
Error rate 1 - 2% means it is available in real life easily.
Connect the data acquistion device NI6009 and Matlab.
Matlab code: 2 Scripts.
1. UltraSensor.m
%% Ultra Sensor %% Device setting a = daq.getDevices % Session for Input(echo) ai = daq.createSession('ni') ai.Rate = 48000; ai.DurationInSeconds = 1; ai.NotifyWhenDataAvailableExceeds = 48000; % Port for Input(echo) aic = addAnalogInputChannel(ai, 'Dev1', 'ai0', 'Voltage') aic.TerminalConfig = 'SingleEnded' aic.Range = [-5.0 5.0] %% % Session for Output(trig) do = daq.createSession('ni') % Port for Output(trig) doc = addDigitalChannel(do, 'Dev1', 'port0/line0:7', 'OutputOnly') % Output Initailization init = [0 0 0 0 0 0 0 0]; one = [1 0 0 0 0 0 0 0]; outputSingleScan(do, init); %% Background global data; global time; global x1; global x2; data = []; time = []; lh = addlistener(ai, 'DataAvailable', @plotData); startBackground(ai) for i = 1:1:1 % 3 times for trigger %pause(0.5) % throw out trash data outputSingleScan(do, one); pause(0.01); % 0,001s > 0.00001s outputSingleScan(do, init); pause(0.1); % 0.1s > 0.06s end %% Distance = Time * Velocity distance = ((x2-x1)*(1/48000) * 340/2)*100 %% cftool x = [20 40 60 80 100]; y = [20.25 39.31 59.5 78.98 98.81] cftool(x,y) |
2. plotData.m
%% Background plotData function -> Data, Time = [] function plotData(src, event) global data; data = [data;event.Data]; global time; time = [time;event.TimeStamps]; global x1; global x2; global flag; flag = 0; for i=1:1:length(event.Data) if event.Data(i) >= 2.5 if flag == 0; flag = 1; x1 = i end else event.Data(i) < 2.5 if flag == 1; flag = 0; x2 = i end end end plot(time,data) end |
The results are as follows
Echo Pulse Output sample
|
ruler measurement(cm) |
2 |
20 |
40 |
60 |
80 |
100 |
180 |
|
Sensor measurement(cm) |
2.75 |
20.25 |
39.3125 |
59.5 |
78.9792 |
98.8125 |
121 |
|
Error rate(%) |
37.5 |
1.25 |
1.72 |
0.83 |
1.28 |
1.19 |
32.8 |
