Hello my name is Kevin Cavell and I’m the Product Manager for the new Agilent Source
Measure Units. These new SMUs are modules that are part of the N6700 modular power system
family. For this demonstration, the SMU will be installed in this N6705B DC Power Analyzer
Mainframe. Now let’s take a look at the new Agilent patented feature we call seamless
measurement ranging. Today’s test set up consists of a demo board connected to the
new N6781A two quadrant SMU for battery drain analysis. This demo board will simulate the
dynamic current that is typical of a battery powered device as it transitions between states
of operation. This type of dynamic power management is used in many battery powered devices such
as mobile phones, ebook readers and medical devices where power consumption is critical.
To control the SMU and analyze the data I will be using the new 14585A Control and Analysis
Software for the DC Power Analyzer. The software is not necessary to use in the DC Power Analyzer,
but it does provide usability enhancements. Right now the SMU’s built-in 200 KHz digitizer
is capturing the dynamic current being sourced to the demo board. You can see the current
pulses here in the scope view mode of the software. Let’s zoom in on one of the pulses
so we can see it better. I’ll change the time base from 200 msec per division to
5 msec per division so we can see the pulse better. These pulses vary between 125 uA and
120 mA. This is a 1000 to 1 change in current which is difficult to measure. Traditionally,
in order to measure a dynamic current such as this, you would have to choose a measurement
range that can capture the higher 120 mA portion of the pulse. In our case, the 3 A measurement
range is the correct range. Let’s use the markers to measure the 120 mA portion of the
pulse. We’ll turn the markers on. Drag the markers over to the pulse. Then we can measure
the average current of approximately 120 mA. If we move the markers over to the lower portion
of the pulse, you can see that the average current is bouncing all over the place. This
is because we cannot make an accurate measurement due to the offset error of the 3 A range.
Thus, in order to capture the entire waveform you sacrifice the low level accuracy needed
to measure the 125 uA portion of the pulse. Let’s zoom in on this portion of the pulse
and take a closer look. I’ll change the amps per division from 50 mA to 1 mA per division.
Now we can see the measurement noise more clearly. Let’s switch the measurement range
to ‘auto’ to show you what you get when you use seamless measurement ranging.
As soon as we turn on ‘auto’ you can see
that the measurement noise disappears. This is because the measurement range is automatically
changed to 1 mA and we are now capturing 125 uA portion of the pulse accurately. You can
see the average measurement is approximately 125 uA. If you zoom back out to see the whole
waveform by changing from 1 mA per division back to 50 mA per division, you can still
see we are accurately measuring the 125 uA and, if I move the markers over, we are still
accurately measuring the 120 mA portion of the pulse without overloading the measurement
system. This concludes the demonstration of how Agilent’s new SMU modules provide insights
into power consumption by enabling engineers to see the complete current waveform they’ve
never seen before from nano amps to amps in one pass in one picture. Thanks for watching.