Hi, I'm Brian Wood, Application Support Engineer for BenchVue.
The free Keysight BenchVue software has revolutionized the ease of use of Keysight instruments by
doing the behind the scenes work for you of automatically locating and connecting to all
instruments it can find on LAN, GPIB and USB.
Then giving you a simple way to control them and retrieve data all without writing a single
line of code.
In this video, I'm going to show you an exciting new feature that we've added to BenchVue in
version 3.0 called Test Flow.
It's a flowchart style sequencer that allows you to create automated tests without programming.
Let's start with an example without using Test Flow.
Suppose you want to create the modern equivalent to a curve tracer to see the VI characteristics
of a transistor as you sweep collector emitter voltage for several settings of base emitter
current and measure the resulting collector current.
We'll do this measurement using a Keysight B2962A power source.
This instrument has two channels and is capable of low current stimulus down into the Femtoamp
range and high voltages, high as 210 volts.
And it can measure the current and voltage it's outputting with six and a half digit
accuracy.
We'll drive the base of a 2N 3904 NPN Transistor with one channel set up as a current source
and then apply various voltages to the collector and measure the resulting collector current.
No extra components are needed.
Let's take a look at how this could be done in BenchVue on a point by point basis manually
setting the voltage and current.
Here I've already started BenchVue which automatically discovered our B 2962A power source and several
other instruments.
We will set the voltage limit to one volt since we only expect one diode drop or .6
volts in the base admitter junction.
We will select the 105 microamp current range and we won't enter more than 100 microamps
of base current.
If the beta of the transistor would say 200, 100 microamps of base current would result
in 20 milliamps of collector current.
But let's select a current limit of 200 milliamps which is the maximum rating of the transistor.
The collector goes to channel two of the SMU, which we will set up as a voltage source.
Which we will manually change from zero to four volts.
Okay, the transistor is connected.
The parameters are set.
So let's turn on both channels.
Now let's set the base current to 20 microamps.
At zero volts, collector voltage we are reading basically no collector current.
Now let's set the collector voltage at 500 millivolts.
The collector current has increased now to four milliamps.
We can repeat this procedure at 40 microamps of base current, manually recording the numbers
and eventually plotting the results.
Now let's see how we can automate this procedure using Test Flow.
We'd like to start by making sure the supply outputs are off.
So we'll drag the on off buttons over to the Test Flow pane and make sure we have selected
off.
We also want to make sure channel one is set up as a current source and channel two as
a voltage source.
Now recall that we want to set the voltage limit on channel one to one volt and the current
limit to 200 milliamps.
When we drag these properties over notice how the flow sequencer defaults to a sweep.
In this case we don't want to sweep these properties.
We just want to set them.
So we can click the gear icon and select sweep get set or list options.
Select set and okay.
We want to initialize the current range to 105 microamps and the voltage range to 21
volts.
Now we want to sweep the base current.
So we'll drag the current setting property over.
We'll sets values in a moment.
For each value of base current we want to sweep the collector voltage, so we can drag
that property inside the base current sweep.
We'll set its values in a moment as well.
We will want a plot of collector current versus collector voltage.
So let's drag those measurements over into the inner sweep loop.
Notice that we started with the outputs off.
We will want to turn them on before we take measurements.
So we can right click on these blocks and select duplicate.
Then we can drag them just prior to our sweeps and turn the outputs on.
We also will want to turn them back off at the end, so we can repeat this procedure,
placing the blocks at the end.
Now let's set the sweep values.
We want the base current to go from 20 microamps to 100 microamps in 20 microamp steps.
We want the collector voltage to go from zero to four volts in 100 millivolt steps.
The minimum available in this case is actually one microvolt, so it was changed for us.
Now to make a nice looking plot, we can change the labels of the current source and the collector
current and collector voltage to more meaningful names.
Our sequence is now done.
So let's maximize the Test Flow window.
Let's double check our flow to make sure everything looks good.
We can also see a chart and a table where our results will show up.
In the table view the value of the parameters at each step are shown when they change.
The chart view gives us a graphical representation of this.
We can look at the values as a time based chart or we can plot anything against anything
else in the XY chart.
So let's select the collector current for the Y axis and the collector voltage for the
X axis.
Now when we click start the familiar shape of a transistor curve trace begins to take
shape.
When it's done we can mouse over the chart to see values at each measurement point.
Trace data and screenshots can be exported in Excel, Word, MATLAB, and CSV formats.
We've shown how to use BenchVue Test Flow and a B2962A power source to make a transistor
curve tracer.
Thanks for watching.