Lab 6 – The RS232 Interface - Lockin Amp

 I. Objective:

To instruct the student in the use of the RS232 interface and compare that interfacing technique with the GPIB interface. Students should realize there are more than one way for different instruments to communicate with each other and the benefits of using one technique over another.

II. Procedure:

Interfacing with RS232:

Duplicate the experiment done in Lab 4, but this time using the lack-in amplifier’s RS232 interface. In addition, the VI must

  1. As part of initialization, check that communication is established with instrument. Generate an error message if communication not established. The simplest method is to request a serial poll byte. If an error is generated, communication is not established. If no error is generated, then communication is established.
  2. communicate with the lock-in amplifier using the RS232 protocols (no GPIB)
  3. disable the front panel controls of the lock-in amplifier when your VI starts.

Additional information and a copy of this lab is located at:

 http://web.njit.edu/~gnita/VI/OPSE310/OPSE310lab_6.htm

Submit the created VI or VIs by attaching them to an e-mail document that contains the answers to the discussion questions below. (Note that you can either attach the VIs or zip the VIs by using WinZIP). E-mail the answers to the discussion questions and the files to:

gnita@njit.edu

III. Discussion:

  1. What is the fastest rate at which you can read data from the lock-in amplifier? To try this, temporarily remove the time delay between data points. See how long it takes to record 100 data points. (Do not plot the data after each data point since this is a high processing overhead for updating graphs and plots in Labview.)
  2. What limits this data acquisition rate? Is it LabVIEW or an instrument? [some experimentation might be necessary to answer this question]
  3. Which is a "Faster" interface for this application GPIB or RS232? To test the GPIB, go bck to your Lab 4 and repeat Discussion Question #1. Make sure that you use the SAME locking and computer for both the GPIB and RS232 tests!
  4. Based on your results with this lab and the equivalent GPIB Lab, which is an easier/ better method for interfacing GPIB or RS232? In answering this question, consider ease of implementation, writing of VI, ability to avoid/ handle errors etc.