Programming Tektronix OpenChoice Oscilloscopes
with LabVIEW
Introduction
LabVIEW is a graphical development environment for acquiring, analyzing and
presenting data. This makes it a good companion to your TDS OpenChoice
oscilloscope with its own data acquisition and analysis abilities.
You use LabVIEW to create virtual instruments, also known as VIs. A LabVIEW
VI consists of a front panel and a block diagram.
The front panel provides the user interface for your program. Use the front panel
to input data and view outputs. Build the front panel with graphical
representations of controls and indicators. A control could be a knob or a switch.
An indicator could be a graticule on which to display oscilloscope-style
waveforms.
The block diagram contains the VI’s underlying code. Build your block diagram
with functions, other VIs and wires. The wires connect the block diagram objects
to each other. You can draw upon LabVIEW’s libraries for data collection,
analysis, presentation, and storage.
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Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
To help you create and edit your program’s front panel and block diagram,
LabVIEW provides palettes. These are shown in the following table:
Palette Appearance Description
Tools
Controls
Use this palette with both the front
panel and the block diagram. The
tools in this palette let you operate
and modify the front panel and
block diagram objects. To display
this palette, go to the front panel or
block diagram menu bar and click:
Windows -> Show Tools Palette
Use this palette with the front panel.
It provides your front panel’s
controls and indicators. To display
this palette, go to the font panel
menu bar and click:
Windows -> Show Controls
Palette
Functions
Use this palette with the block
diagram. It provides your block
diagram’s functions and VIs. To
display this palette, go to the block
diagram menu bar and click:
Windows -> Show Functions
Palette
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Programming Options
Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
The functions palette includes oscilloscope-specific sub-palettes for each of the
TDS5000, 6000, 7000, and 8000 series open Windows oscilloscopes. You can
use them to manage waveform transfer between your LabVIEW applications and
your TDS open Windows oscilloscope.
You can use either VISA I/O functions or VXIplug&play instrument drivers to
communicate with your oscilloscope.
Advanced users can use VISA to send and receive text-based messages to the
oscilloscope directly. You may want to use this method if you need complete
control of how the instrument is programmed. This method has a higher learning
curve than using an instrument driver. However, there are some opportunities for
optimization if you are familiar with the GPIB command set.
Most users should use VXIplug&play driver to access all the oscilloscope
functionality from LabVIEW. Tektronix has worked with National Instruments to
provide LabVIEW wrappers that are customized for all Tektronix OpenChoice
oscilloscopes. Note that the instrument drivers have to be installed after installing
LabVIEW. These LabVIEW wrappers provide a convenient way of accessing the
different functions in the driver. You can access these wrappers from the
Functions-> Instrument Drivers palette as shown in the following illustration:
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Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
These VIs communicate with the oscilloscope through the standard Tektronix
VXIplug&play instrument drivers and simplify tasks, such as transferring
waveforms, timing and scaling information to and from LabVIEW.
The oscilloscope specific VIs simplifies these tasks by grouping related
operations. For example, The Simple Get Waveform VIs can acquire waveform
signals from a live source such as a channel, reference or math source or from a
file. This article provides step-by-step instructions on building an example using
these oscilloscope specific VIs.
Another option for communicating with your instrument is to use ActiveX. You
can work with TVC and IVI-COM drivers using the ActiveX support provided
by LabVIEW. An article in the SDK (Using the TekScope IVI-COM Driver in
LabVIEW) provides step-by-step instructions on how to set up a sample VI in
LabVIEW using a Tektronix IVI-COM driver. Unlike the Plug and Play drivers,
customized wrappers are not provided for Tektronix IVI-COM drivers.
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Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
A Simple LabVIEW Demo
The purpose of this demo is to familiarize you with creating a LabVIEW virtual
instrument on your open Windows oscilloscope. The input is a simple probe
compensation signal. The output is a graph of that signal. The demo assumes that
you have an open Windows TDS5000, 6000, 7000 or 8000 series oscilloscope
with LabVIEW installed on it, and a cable connecting your oscilloscope’s probe
compensation signal to channel 1. Press the oscilloscope’s front-panel
AUTOSET button to obtain a clear view of the probe compensation signal.
Minimize the oscilloscope application.
a. Start LabVIEW from Windows by clicking on:
Start -> National Instruments -> LabVIEW 6.1 -> LabVIEW
You should see a
LabVIEW window, as
shown in the figure to the
right.
b. VI Creation
Click the button labeled New
VI. This brings up a blank
front panel and a blank block
diagram, as shown to the
right.
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Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
c. Front Panel Creation
Create your virtual
instrument user interface. In
this demo, you will do that
by creating a front panel
with an oscilloscope display
on it. To do this, click the
front panel’s menu bar,
Window->Show Controls
Palette, as shown to the
right.
This will bring up the
Controls palette.
Then select the Graph icon
in the palette. This brings up
the Graph sub-palette.
Click on the Waveform
Graph control from the subpalette. Then click the front
panel to place the
Waveform Graph on the
front panel, as shown to the
right.
Move the indicator in your front panel as desired. To do that, bring up the
Positioning tool
pull-down menu on the front panel window. Click positioning icon in that palette.
. Do this by selecting Show Tools Palette from the Window
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Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
Use the positioning cursor to position the Waveform Graph as you want on the
front panel window.
d. Block Diagram Creation
Create your instruments’ underlying code by developing the block diagram. On
the Block Diagram window’s menu bar, click Window-> Show Functions
Palette to bring up the Functions palette. Click Instrument Drivers item in the
palette to bring up the Instrument Drivers palette. It should contain an icon for
your series of TDS open Windows oscilloscope.
Put the VIs for the oscilloscope functions you want to use on your block diagram.
In this demo, we are using four VIs to demonstrate waveform data capture from
an instrument. The four VIs are Initialize, Get Horizontal Record Length, Get
Waveform, and Close. To do this,
click each of these functions in the drivers
palette and then click on your block diagram, as shown in the following
figure:
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Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
You can further position the function blocks with the position tool from the Tools
palette.
e. Set Values
Now define a constant of a function to set. Do this by first selecting the Wiring
tool from the Tools palette. Then move it to the input (left side) of the Initialize
VI labeled reset device. Right-click your mouse and select Create-Constant
from the resulting menu, as shown in the following figure:
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Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
Now set the value of that constant. Do this by selecting the Operating tool from
the Tools palette.
Then click on the reset device constant. Set the value to F, for false.
Now, set another value. Once again select the Wiring tool from the Tools
palette. Then right-click the VISA resource name input on the left side of the
Initialize VI. Select Create-Constant from the menu. If GPIB8::1::INSTR
does not appear, check that your TekScope application is running. You can
specify any other valid VISA resource name in place of GPIB8::1::INSTR.
You have now added all the VIs (objects) on your block diagram needed to
process the data.
f. Wiring the VI
The next step is to enable the VIs on your block diagram to communicate with
each other. To do this, use the Wiring tool from the Tools palette.
Select the Wiring tool. Wire the following connections:
1. Connect the Instrument Handle Out terminal of the Initialize VI to the
Instrument Handle In terminal of the Get Horizontal RecordLength VI.
2. Connect the Instrument Handle Out terminal of the Get Horizontal
RecordLength VI to the Instrument Handle In terminal of the Get Waveform
VI.
3. Connect the RecordLength Terminal of the Get Horizontal RecordLength VI
to the Waveform Size Input of the Get Waveform VI.
4. Connect the Waveform output terminal of the Get Waveform VI to the
Waveform Graph indicator terminal.
5. Connect the Instrument Handle Out terminal of the Get Waveform VI to the
Instrument Handle terminal of the Close VI.
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Programming Tektronix OpenChoice Oscilloscopes with LabVIEW
g. Running the VI
The last step is to start the program. To do this, simply click on the Run button.
In this demo, a waveform
should then appear on the
front panel waveform
indicator, as shown to the
right.
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