Lab 4 – The GPIB Interface - Function Generator

I. Objective:

To give the student experience in handling GBIP interfacing and to show the student how computers and other pieces of equipment communicate with each other. Experience in these fields will aid in the transition between using LabVIEW as a virtual instrument and using LabVIEW as an actual aid in research and data acquisition.

II. Procedure:

Writing a simple GPIB interface for the HP33120A

Write a VI (you can break it into subVIs if you wish) which performs the following for the HP33120A:

  1. During the Initialization procedures, read the current HP33120A's front panel values of the wave type, amplitude, and frequency and display them on your VI front panel. If these values change using the controls for (b), (c), or (d) below, then the displays should change as well.
  2. Controls the type of wave: (sine wave, square wave, triangular wave, sawtooth). Make sure to update your wave type display.
  3. Controls the wave amplitude. Make sure to update your wave amplitude display.
    4.
  4. Controls the wave frequency. Make sure to update your wave frequency display.

Features (b), (c), (d) might be most effectively implement using a "change settings" switch on the front panel which then pops up a sub-VI.

  1. Aside from the controls listed above, put a Boolean switch on the Front Panel. When the user pushes the switch, the wave amplitude is changed from 0.1 to 1 volt in 0.1V increments. The user should be able to vary the delay between the changing of the wave amplitude from 1 to 10 seconds. Display a numeric indicator of the current wave amplitude point and display the wave amplitude data as it is being generated using a chart recorder.

III. Discussion:

  1. A VI front panel item can only be an indicator OR a control. How did you handle the problem of setting the amplitude, frequency and wave type to their current values during initialization, but allow them to change during the running of the VI?
  2. Should the user be allowed to change the type of wave or amplitude DURING the acquisition of data from an experiment? Why or Why not?

Please email your discussion questions responses and the VI (and all required SubVIs) to gnita@njit.edu