General Purpose Interface Bus in Data Acquisition and Control

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Santiago Salazar
Chris Paulino
12/15/11
Florida Gulf Coast University
Dr. Zalewski

Previous project by Olexiy Kovtunenko and Robert Porter.
They Created a LabView Program to communicate with 2 GPIB devices.
The devices are a HP 34401A multimeter which gets voltage measurements , and a
HP 53131A Universal Counter which counts the measurements per second.
We planned to connect another GPIB device to the other two and have it
communicate with the LabView program. The device is a HP 33120A Function /
Arbitrary Waveform Generator. It generates waves with changeable settings
HP 34401A multimeter HP 53131A Universal Counter HP 33120A Function /
Arbitrary Waveform Generator

The waveform generator and the other GPIB devices are connected to the
computer with GPIB cables.
The GPIB cables are connected in serial fashion
The cables on the multimeter and waveform generator are both connected
to the cable on the counter.
The cable on the counter is connected to the computer
This allows them all to communicate with the computer

We used a BNC cable to connect the counter and the multimeter to the
waveform generator. One BNC cable is connected from Channel 1 on the
counter to Sync on the waveform generator.
Instead of an ordinary BNC cable, the multimeter needed a BNC to
Regular Battery cable. The BNC part is connected to “Output” on the
waveform generator. The positive and negative battery connections are
connected to the input on the multimeter.

The LabView program communicates with the GPIB devices by using string
commands.
An example of a command that can be sent to the waveform generator to control
its settings:
APPL:SIN 0.1 HZ, 1.0 VPP, 0 V
Creates a sine wave at a frequency of 0.1 Hz, 1.00 VPP amplitude and a offset of 0 V.
The wave, frequency, amplitude and offset can all be changed around.
“READ?” is a command sent from the program to the counter and the multimeter
to read the data each device is outputting.

The front panel of our LabView Program is shown below
It displays a graph of the specified wave at the specified frequency which measures
voltage against time.
The Sample # text box reads from the counter and displays the number of
measurements taken.
Multimeter Data and Counter Data text boxes display the what is being outputted
from each respective device. Only voltage can be used for the multimeter and we
chose to use frequency for the counter. Either dc or ac voltage measuring can be
selected from the radio buttons
The address boxes are for the user to enter the address of each device so that the
program can communicate with the devices.
The program can be started and stopped on the front panel via buttons.

The block diagram of our LabView Program is shown below
Mainly, it consists of a main while loop, which contains commands that ask the
devices to send data measurements back to the PC
Each iteration of the main while loop sends a single data measurement from both the
multimeter and the counter back to the PC
It also involves case structure used to select which type of voltage is to be read
An event case structure sends commands to the waveform generator whenever the
user click on the appropriate button
Buttons are used to break the while loops
When the main while loop is broken, the program stops running

We incorporated the ability to use generated waveforms. By using a BNC
to regular battery cable to connect the multimeter with the waveform
generator
We added a Universal Counter to the other two GPIB devices and
connected it to the waveform Generator with a regular BNC cable.
However it only reads accurate data at frequencies of 10 Hz and above

We created a new LabView program that would work properly with the
Universal Counter
We added a textbox to display the output of the counter
We added a textbox to display the number of measurements taken
We added textboxes for the addressing of each GPIB device so that the
user may change the address if necessary
We added the ability to set the parameters of the waveform generator
from the LabView program itself

We started the project not knowing how to interconnect the GPIB
devices
Another complication we encountered was how to send
commands to the Waveform Generator
The Universal Counter presented some technical problems as we
found out it could only read 10 Hz and above when our project
required much less than that
We did research using the manuals of each device to figure out
how to connect them and send commands to them
Our project works almost exactly the way we want it to. The only
problem is reading low frequencies from the counter as mentioned
above