acquire data using ni devices -凯发k8网页登录

this example shows how to acquire data from a national instruments device.

discover analog input devices

to discover a device that supports input measurements, access the device in the table returned by the daqlist command. this example uses an ni 9201 module in a national instruments® compactdaq chassis ni cdaq-9178. this is an 8 channel analog input device and is module 4 in the chassis.

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{4, "deviceinfo"}

deviceinfo = 
ni: national instruments ni 9201 (device id: 'cdaq1mod4')
   analog input supports:
      -10 to  10 volts range
      rates from 0.6 to 500000.0 scans/sec
      8 channels ('ai0' - 'ai7')
      'voltage' measurement type
   
this module is in slot 4 of the 'cdaq-9178' chassis with the name 'cdaq1'.

create a dataacquisition and add analog input channels

create a dataacquisition, set the rate property (the default is 1000 scans per second), and add analog input channels using addinput.

dq = daq("ni");
dq.rate = 8000;
addinput(dq, "cdaq1mod4", "ai0", "voltage");
addinput(dq, "cdaq1mod4", "ai1", "voltage");

acquire a single scan as a table

use read to acquire a single scan. the result is a table with two data columns because two input channels are used to acquire the scan.

tabledata = read(dq)

tabledata =
  1×2 timetable
    time     cdaq1mod4_ai0    cdaq1mod4_ai1
    _____    _____________    _____________
    0 sec     0.00081472       0.00090579

acquire a single scan as a matrix

use read to acquire a single scan. the result is an array of size 1x2 because two input channels are used to acquire the scan.

matrixdata = read(dq, "outputformat", "matrix")

matrixdata =
   1.0e-03 *
    0.1270    0.9134

acquire data for a specified duration

use read to acquire multiple scans, blocking matlab execution until all the data requested is acquired. the acquired data is returned as a timetable with width equal to the number of channels and height equal to the number of scans.

% acquire data for one second at 8000 scans per second.
data = read(dq, seconds(1));

plot the acquired data

plot(data.time, data.variables);
ylabel("voltage (v)")

acquire specified number of scans

data = read(dq, 2*dq.rate);
plot(data.time, data.variables);
ylabel("voltage (v)")