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 = 2;
w = 2*pi*freq;
t = linspace(0,10,10000);
data = 2*sin(w*t)';

Configure the sampling rate to 2 kHz, configure the trigger to repeat two times, and scale the data to cover the full output range of the D/A converter. Since 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',2000)
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)
while strcmp(AO.Running,'On')
end

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