Log Analog Input Data to a File Using NI Devices

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This example shows how to save data acquired in the background to a file.

Create a DataAcquisition with Analog Input Channels

Create a DataAcquisition and add two analog input channels withVoltagemeasurement type. For this example use a National Instruments® X Series data acquisition device, NI PCIe-6363 card with IDDev1.

d = daqlist("ni")

d = 12×4 table DeviceID Description Model DeviceInfo ___________ __________________________________ _____________ ____________________ "cDAQ1Mod1" "National Instruments NI 9205" "NI 9205" [1×1 daq.DeviceInfo] "cDAQ1Mod2" "National Instruments NI 9263" "NI 9263" [1×1 daq.DeviceInfo] "cDAQ1Mod3" "National Instruments NI 9234" "NI 9234" [1×1 daq.DeviceInfo] "cDAQ1Mod4" "National Instruments NI 9201" "NI 9201" [1×1 daq.DeviceInfo] "cDAQ1Mod5" "National Instruments NI 9402" "NI 9402" [1×1 daq.DeviceInfo] "cDAQ1Mod6" "National Instruments NI 9213" "NI 9213" [1×1 daq.DeviceInfo] "cDAQ1Mod7" "National Instruments NI 9219" "NI 9219" [1×1 daq.DeviceInfo] "cDAQ1Mod8" "National Instruments NI 9265" "NI 9265" [1×1 daq.DeviceInfo] "Dev1" "National Instruments PCIe-6363" "PCIe-6363" [1×1 daq.DeviceInfo] "Dev2" "National Instruments NI ELVIS II" "NI ELVIS II" [1×1 daq.DeviceInfo] "Dev3" "National Instruments PCIe-6363" "PCIe-6363" [1×1 daq.DeviceInfo] "Dev4" "National Instruments PCIe-6363" "PCIe-6363" [1×1 daq.DeviceInfo]

deviceInfo = d{9,"DeviceInfo"}

deviceInfo = ni: National Instruments PCIe-6363 (Device ID: 'Dev1') Analog input supports: 7 ranges supported Rates from 0.0 to 2000000.0 scans/sec 32 channels ('ai0' - 'ai31') 'Voltage' measurement type Analog output supports: -5.0 to +5.0 Volts,-10 to +10 Volts ranges Rates from 0.0 to 2000000.0 scans/sec 4 channels ('ao0','ao1','ao2','ao3') 'Voltage' measurement type Digital IO supports: 39 channels ('port0/line0' - 'port2/line6') 'InputOnly','OutputOnly','Bidirectional' measurement types Counter input supports: Rates from 0.1 to 100000000.0 scans/sec 4 channels ('ctr0','ctr1','ctr2','ctr3') 'EdgeCount','PulseWidth','Frequency','Position' measurement types Counter output supports: Rates from 0.1 to 100000000.0 scans/sec 4 channels ('ctr0','ctr1','ctr2','ctr3') 'PulseGeneration' measurement type

dq = daq("ni"); addinput(dq,"Dev1", 0:1,"Voltage"); dq.Channels

ans = Index Type Device Channel Measurement Type Range Name _____ ____ ______ _______ ________________ __________________ __________ 1 "ai" "Dev1" "ai0" "Voltage (Diff)" "-10 to +10 Volts" "Dev1_ai0" 2 "ai" "Dev1" "ai1" "Voltage (Diff)" "-10 to +10 Volts" "Dev1_ai1"

Create a Log File

Create the filelog.binand open it. The file identifier is used to write to the file.

fid1 = fopen("log.bin","w");

Set the ScansAvailableFcn

During a background acquisition, the DataAcquisition can be directed to handle acquired data in a specified way using theScansAvailableFcnproperty.

dq.ScansAvailableFcn = @(src, evt) logData(src, evt, fid1);

Acquire Data in the Background

Usestartto acquire data for five seconds.

start(dq,“持续时间”, seconds(5))

During normal operation, other MATLAB commands can execute during this acquisition. For this example, usepausein a loop to monitor the number of scans acquired for the duration of the acquisition.

whiledq.Running pause(0.5) fprintf("While loop: Scans acquired = %d\n", dq.NumScansAcquired)endfprintf("Acquisition has terminated with %d scans acquired\n", dq.NumScansAcquired);

Close the Log File

fclose(fid1);

Load Data From the Log File

Load file contents as a 3-column matrix into数据.

fid2 = fopen('log.bin','r'); [data,count] = fread(fid2,[3,inf],'double'); fclose(fid2);

Assign and Plot the Data

t = data(1,:); ch = data(2:3,:); plot(t, ch);

functionlogData (src, ~, fid)(数据、时间戳~)=阅读(src, src.ScansAvailableFcnCount,"OutputFormat","Matrix"); data = [timestamps, data]' ; fwrite(fid,data,'double');end

While loop: Scans acquired = 500 While loop: Scans acquired = 1000 While loop: Scans acquired = 1500 While loop: Scans acquired = 2000 While loop: Scans acquired = 2500 While loop: Scans acquired = 3000 While loop: Scans acquired = 3500 While loop: Scans acquired = 4000 While loop: Scans acquired = 4500 While loop: Scans acquired = 5000 Acquisition has terminated with 5000 scans acquired

Data Acquisition Toolbox Documentation

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