Acquire Counter Input Data

Add Counter Input Channel

Use addinput to add a channel that acquires edge counts from a device. You can acquire a single input data or an array by acquiring in the foreground. For more information, see Interface Workflow.

Acquire a Single Count

This example shows how to acquire a single count of falling edges from an NI 9402 with device ID cDAQ1Mod5. The example assumes that some external source is providing an input to the counter channel, and that the count is accumulating over time. You can read the accumulated count at one point in time, then reset the counter and read it again at a later time.

Step 1. Create a DataAcquisition object assigned to the variable d.

d = daq("ni");

Step 2. Add a counter input channel with an edge count measurement type.

ch = addinput(d,"cDAQ1Mod5","ctr0","EdgeCount")
ch = 

    Index    Type      Device       Channel    Measurement Type    Range         Name    
    _____    ____    ___________    _______    ________________    _____    ________________

      1      "ci"    "cDAQ1Mod5"    "ctr0"       "EdgeCount"       "n/a"    "cDAQ1Mod5_ctr0"

Step 3. Change the channel ActiveEdge property to 'Falling' and view the channel properties to see the change.

ch.ActiveEdge = 'Falling';
get(ch)
      ActiveEdge: Falling
  CountDirection: Increment
    InitialCount: 0
        Terminal: 'PFI0'
SampleTimingType: 10388
            Name: 'cDAQ1Mod5_ctr0'
              ID: 'ctr0'
          Device: [1x1 daq.ni.DeviceInfo]
 MeasurementType: 'EdgeCount'

Step 4. Acquire a single scan reading of the counter buffer.

count = read(d)
count =

   133

Step 5. Reset counters from the initial count and acquire an updated count value. This value is the number of detections since resetting the counter.

resetcounters(d);
count = read(d)
count = 

   71

Acquire a Single Frequency Count

This example shows how to acquire a single scan of frequency measurement from an NI 9402 with device ID cDAQ1Mod5.

Step 1. Create a DataAcquisition object.

d = daq("ni");

Step 2. Add a counter channel with a frequency measurement type.

addinput(d,"cDAQ1Mod5","ctr0","Frequency")
    Index    Type      Device       Channel    Measurement Type    Range         Name    
    _____    ____    ___________    _______    ________________    _____    ________________

      1      "ci"    "cDAQ1Mod5"    "ctr0"       "Frequency"       "n/a"    "cDAQ1Mod5_ctr0"

Step 3. Acquire a single scan of counter data.

f = read(d,"OutputFormat","Matrix")
f =

  9.5877e+003

Acquire Counter Input Data in the Foreground

This example shows how to acquire rising edge data from an NI 9402 with device ID cDAQ1Mod5, and plot the acquired data.

Step 1. Create a DataAcquisition object.

d = daq("ni");

Step 2. Add a counter input channel with an edge count measurement type.

addinput(d,"cDAQ1Mod5","ctr0","EdgeCount")
    Index    Type      Device       Channel    Measurement Type    Range         Name    
    _____    ____    ___________    _______    ________________    _____    ________________

      1      "ci"    "cDAQ1Mod5"    "ctr0"       "EdgeCount"       "n/a"    "cDAQ1Mod5_ctr0"

The counter input channel requires an external clock to perform a foreground acquisition. If you do not have an external clock, add an analog input channel from a clocked device on the same CompactDAQ chassis to the DataAcquisition. This example uses an NI 9205 device on the same chassis with the device ID cDAQ1Mod1.

Step 3. Add an analog input channel for a voltage measurement type.

addinput(d,"cDAQ1Mod1","ai1","Voltage");

Step 4. Acquire the data and assign it to the variable data, and plot the results.

data = read(d,seconds(1),"OutputFormat","Matrix");
plot(data)

The plot displays the results from both channels in the DataAcquisition:

  • Edge count measurement

  • Analog input data