Data Acquisition Toolbox

Example: Performing a Linear Conversion

This example illustrates how to configure the engineering units properties for an analog output object connected to a National Instruments PCI-6024E board.

The queued data consists of a 4 volt peak-to-peak sine wave. The UnitsRange property is configured so that queued data is scaled to the OutputRange property value, which is fixed at ±10 volts. This scaling utilizes the maximum dynamic range of the analog output hardware.

You can run this example by typing daqdoc6_6 at the MATLAB command line.

1. Create a device object -- Create the analog output object AO for a National Instruments board. The installed adaptors and hardware IDs are found with daqhwinfo.

• AO = analogoutput('nidaq',1);
  

2. Add channels -- Add one hardware channel to AO.

• chan = addchannel(AO,0);
  

3. Configure property values -- Create the data to be queued.

• freq = 500;
  w = 2*pi*freq;
  t = linspace(0,2,20000);
  data = 2*sin(w*t)';
  

1. Configure the sampling rate to 5 kHz, configure the trigger to repeat two times, and scale the data to cover the full output range of the D/A converter. Because the peak-to-peak amplitude of the queued data is 4, UnitsRange is set to [-2 2], which scales the output data to 20 volts peak-to-peak.

   • set(AO,'SampleRate',5000)
     set(AO,'RepeatOutput',2)
     set(chan,'UnitsRange',[-2 2])
     

   Queue the data with one call to putdata.

   • putdata(AO,data)
     

4. Output data -- Start AO and wait until all the data is output.

• start(AO)
  waittilstop(AO,6)
  

5. Clean up -- When you no longer need AO, you should remove it from memory and from the MATLAB workspace.

• delete(AO)
  clear AO
  

Linearly Scaling the Data: Engineering Units

Starting Multiple Device Objects