My PowerLab only has two channels. How can I get stimulus markers to be displayed on channel 3?

Output channel markers can only be displayed on input channels, because they are generated by the PowerLab to guarantee precision timing. If you can’t use a sampling channel to display the markers, you can use Computed Inputs to copy the input data of (for example) Channel 1 and display it on Channel 3.
  1. To turn on a Computed Input channel, open the Channel Settings dialog (Ctrl+Y) and turn on Channel 3.
  2. The Computed Input column should be set to Raw Data Input 1.
  3. Click OK
You will now be able to configure the Stimulator to show the stimulus marker on Channel 3 (or any other channel that uses Computed Inputs)

If you only want the markers, and not the data, simply use an Arithmetic channel calculation to subtract the sampled data from channel 1. For example, for Channel 3:
= Ch3 - Ch1
NB This information is valid for LabChart 7 or earlier.  Customers using LabChart 8 only have the option to utilise the input channels.