Programming with VISA

Summary: In this exercise, the objective is to build a VI that reads and writes information from the NI Instrument Simulator using VISA functions. Complete the following steps to build a VI that uses VISA calls to acquire data from the NI Instrument Simulator.

1. Make sure the Instrument Simulator is powered on and connected to the GPIB Interface.

Front Panel

1. Open a blank VI. The front panel shown in Figure 1 will result from building the block diagram.

   Figure 1

Block Diagram

1. Build the block diagram shown in Figure 2.

   Figure 2

   1.  Place the VISA Open function, located on the Functions>>All Functions>>Instrument I/O>>VISA>>VISA Advanced palette, on the block diagram. This function opens a VISA session with an instrument. Right-click the VISA resource name input and select Create>>Control from the shortcut menu.
   2.  Place the VISA Write function, located on the Functions>>All Functions>>Instrument I/O>>VISA palette, on the block diagram. This function writes a string to the instrument. Right-click the write buffer input and select Create>>Control from the shortcut menu.
   3.  Place the VISA Read function, located on the Functions>>All Functions>>Instrument I/O>>VISA palette, on the block diagram. This function reads data from the instrument. Right-click the byte count input and select Create>>Control from the shortcut menu. Right-click the read buffer output and selectCreate>>Indicator from the shortcut menu.
   4.  Place the VISA Close function, located on the Functions>>All Functions>>Instrument I/O>>VISA>>VISA Advanced palette, on the block diagram. This function closes the session with the instrument and releases any system resources that were used.
   5.  Place the Simple Error Handler VI, located on the Functions>>All Functions>>Time & Dialog palette, on the block diagram. This VI checks error conditions and opens a dialog box with error information if an error occurs.
2. Save the VI as My VISA Write & Read.vi in the C:\Exercises\LabVIEW Basics I directory.
3. Display the front panel. Enter devsim in the VISA resource name input and set byte count to 200 to make sure you read all the information. Type *IDN? in the write buffer and run the VI.
4. The top of the instrument simulator lists other commands that are recognized by this instrument. Try other commands in this VI.
5. Close the VI when finished.

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