Hi, I’m Brian Wood.
I’m an Application Engineer for BenchVue and today we’re going to talk about how
to capture things in the oscilloscope app that are not part of BenchVue using command
expert and test flow.
All right, so I’ve started BenchVue and selected a Keysight 4000 series scope.
As I go from the Bench tab to the Apps tab, Data Manager, Library, you can see the various
features of BenchVue.
One of the things that is very useful is the library tab.
So in this demo, I’m going to be needing to get access to some of the low level programming
commands for the oscilloscope.
The easiest way to find out what those are is through the manual so I can come over here
to manuals.
I can click the programmers guide and as long as I’m connected to the internet, I will
be able to get the data sheet for the oscilloscope.
Today we’re going to be showing you how to do a mask test using the oscilloscope and
so I’m going to search for mask test and it tells me it’s in chapter 24.
I can go to the introduction and here I now see some sample code that tells me how to
use that feature in the application.
So now that I know what the commands are going to be and in what order I need to execute
them, I can do that from BenchVue.
But how do I do that?
The commands are not available in the app itself as.
I go look at the different tabs here, instrument settings, Screen Image, Trace Data, Measurement
Data Log, I can select Channels.
I can increase and decrease the vertical and horizontal resolution.
I can set triggers, but I can’t send low level SCPI commands.
To do that, I have to start BenchVue test flow.
All right and in test flow, if I already know the commands, I can go over to the More Blocks
section, click on Advanced, and drag the SCPI block over into the test flow sequence.
I can give it the address of the instrument and then start typing commands such as star
IDN?.
If I don’t know those commands, I’m going to need some help and where I get that is
command expert.
I can drag command expert over into the sequence and when I click this symbol right here, it
will start command expert in a separate screen and as soon as it comes up, I’ll be able
to create a sequence from command expert.
The first step is to locate your instrument and as soon as you’ve found it –
all right, so now I’ve got my oscilloscope in my instruments.
I can now connect to it and now I see a list of all the available SCPI commands.
I also see some additional commands down at the bottom that are kind of more global things
that allow me to change timeouts, turn on and off the air queries, and things like that.
But if I want to get the mask test in particular, I will go down here to M test, which is what
the manual told me I need to do and I see all the available choices for the mask test.
Let’s just pick one.
Let’s say I need to enable it.
Over here on the right is a description of the enable command.
I can now add that step and if it needs variables or it needs some special command added to
it, it lets you select those so let’s turn enable on and add the step.
As you can see, it’s fairly straightforward to select a SCPI command, read about it, add
the step into the sequence.
You can also create variables that can be exported to the add on.
When I do that, when I click export to add on, it has now inserted that command expert
sequence in the BenchVue test flow sequence.
That’s all there is to that.
Let me load a program that I’ve previously created that will do a complete mask test
and we can step through it line by line and just see what’s going to happen.
Okay, here’s a sequence that involves – actually it calls command expert three times.
The first time is to do the initialization.
In this sequence, I am doing an enable.
That’s the command that I just showed you before.
I can select a source channel, tell it I want divisions for my units.
I can set the X delta and the Y delta, which is the – basically the difference between
the nominal signal and where you’re going to define an error to occur.
The create command then will actually create the mask and we’re going to give it a certain
length of time.
All right, so that basically just sets the thing up without actually executing anything.
I did create two variables, the X delta and the Y delta, and I used test flow to define
those variables.
If I look under my variables block, I can see an x-delta and a y-delta that I’ve created.
It allows me to define those at the beginning of the sequence in case I want to change it
easily.
All right and then I – so at the end of this first command block, I’ve got the instrument
set up to do a mask test.
What I want to do then is apply a signal that’s different so I will at that point change the
voltage intensity of the signal going in so that it will generate a failure.
Then I call command expert again just to start the oscilloscope so put it in run mode.
In this case, the only command in here is a run command.
When I’m done with that, and I again have to wait a couple of seconds for the actual
acquisition to finish, I’ll call command expert a last time and go retrieve the wave
forms that have failed, in other words, the count of the number of wave forms that have
failed and the total number of wave forms that were captured.
And finally, I want to actually get a screen capture of the results so what I did here
is go into the screen image tab and drag get current screen into my test sequence just
like I’m doing here.
And then at the very end, I output the number of total and the number of failed wave forms.
Those will show up over in the table data on the right so let’s go ahead and execute
it.
When I hit run, the scope has captured the nominal wave form and applied the mask to
it which you can see on the oscilloscope itself, and what I’ll do now is change the voltage
and hit continue.
When I do that, it’s going to fail so the test will generate a wave form that is outside
the limits set by the mask test.
At that point, I can – I have captured the screen.
I can double click over here in the table data, bring up the wave form that it captured,
and at that point, I can export it into Word or into a screenshot and that’s it.
It’s as simple as that.