| Analog output scripts
Analog output scripts let you program timed sequences of analog
output voltages ("scripts") from either of the two analog output
channels on National Instruments cards. These can be used to control
any instrument or other external device that responds to voltages (0-5 volt
range). You can program two separate scripts, one for each channel,
that run simultaneously and independently (but you cannot use channel 2
for both output scripts and feedback control at the same time). There
are separate (but identical) menu selections for setting up scripts for
each of the two AO channels ("Analog out #1 script" and
"Analog out #2 script").
Each AO script can contain up to 100 steps. For each step you need to specify:
When these data are entered, press the 'add step' button to append the step to the script. As steps are added or modified, the computer shows a graphical display of the current script, including the total number of steps and the cumulative time (see example below).
For the script as a whole, you need to set:
Scripts may loop back upon themselves, in which case they will run indefinitely unless interrupted by an ending condition or by the conclusion of sampling. A loop can return to any step in the script.
You may modify a script by editing any step ('update' button), appending new steps ('add step' button), inserting new steps into the middle of the sequence ('insert' buttons), removing any step ('delete' button), or removing the entire script ('clear' button).
You can store and retrieve output scripts using the Open and Save selections in the D-A menu.
The AO script setup window looks like the example at right:
This script (for output channel 1) contains 13 steps (plus a returning 'loop' step) lasting a total of 17 minutes. Ramped outputs occur in steps 1, 2, 4, 6, 8, 10, and 12. At the end of the sequence, a loop returns control to the first step. The script sequence will terminate if the "x" key is struck. It will start when the "s" key is struck (this is shown being selected from the pop-up menus in the upper right corner of the window). The pre-run voltage is zero and the post-run condition (when the "x" key is struck or data gathering ceases) is to switch to a value of zero volts.