Data Acquisition Toolbox

Math and Reference Channels

In addition to hardware channels, you can display

• Reference channels -- The data associated with a reference channel is defined from a MATLAB variable or expression. You should use reference channel data as a known waveform against which other data is compared.
• Math channels -- The data associated with a math channel is calculated in MATLAB using the data from existing hardware channels, math channels, or reference channels.

You use the Channel pane of the Channel Editor GUI to create math and reference channels. You open this GUI by selecting the Edit->Channel menu item. For example, suppose you want to create a reference waveform to compare to the CH0 waveform. The first step is to create the reference data in MATLAB:

• t = 0:0.0001:0.2;
  w = 200*2*pi;
  ref = 3.75*sin(w*t);
  

The next step is to define the reference channel in the Channel Editor GUI. The Channel pane shown below is configured to create a reference channel called r1 using the data defined in the variable ref, and to display the reference channel data with CH0 in display2.

Note that instead of creating the variable ref in the workspace, you can specify the expression 3.75*sin(w*t) in the Expression field.

Defining a math channel is similar to defining a reference channel. The main difference is in specifying the expression. For a reference channel, you specify a MATLAB variable or expression. For a math channel, you specify

• The channel name -- Channel names are given by the Name column in the Defined channels table.
• A valid MATLAB expression -- When the expression is evaluated, the channel names are replaced with the associated data that is currently being displayed.

The Channel pane shown below is configured to create a math channel called m1 using the CH0 and CH1 data, and to display the math channel data with CH1 in display1.

The traces for the hardware, math, and reference channels are shown below.

Configuring Display Properties

Removing Channel Displays