All of our power supplies offer the ability to take an
average measurement using either the front panel or the MEAS SCPI
commands. Some of our newer power
supplies have some more advanced measurement capabilities. The
two capabilities that we are going to look at today are digitized measurements and
datalogging. Let’s take a short look at
each one and then talk about when to use each one.
The digitizer has been in our products for a while now. With the digitizer, you define three parameters
and the measurement uses these parameters to return an array of measurements
back to you. The three parameters are:
the number of points, the time interval, and the points offset. The number of points is pretty simple. It is the number of measurements that you
want to take as well as the size of the array that you are going to read back. The time interval is the pace of the
measurements. This is also the time
between the points in the array. The
points offset is a way that you vary the starting point of the array. This offset can be negative to return
measured points before the trigger or positive to delay the start of the
measurement. The most points that we can
measure and the fastest time interval is with our N678xA SMU modules. These modules have a time interval of 5.12 us
and a total number of points of 512 Kpoints (keep in mind that 1 Kpoint is
1,024 points). This yields a total time
of 5.12 us x 512 x 1,024 which yields a result of 2.68 seconds. So the longest measurement that you can make
is 2.68 seconds. The largest time
interval that we can measure is 40,000 seconds.
Setting this with the highest number of points would yield 40,000 s x
512 x 1,024 yields a total acquisition of 20,971,520,000 seconds. That is 666.83 years!
The other advanced measurement capability that we are going
to talk about is our datalogger. With
the datalogger, you set a total acquisition time and an integration time. The integration time is the amount of time
that the power supply will average measurements. The measurement system is still running at
its maximum digitizing rate but it is averaging those measurements and
returning that averaged measurement. The
digitizer on the N6705B DC Power Analyzer also will return the maximum measured
value and the minimum measured value of each integration period. The quickest integration time on the N6705B
is 20.48 us. The only limitation in the
amount of data that you can log with the internal datalogger is the file size
(the maximum file size is somewhere near 2 gB).
If you want to datalog huge files, you can use the external datalog
feature (I wrote another blog post about this) or use our 14585A software where
the only limitation is the free space on your hard drive. The catch on the external datalogger is that
that the quickest integration time is 102 us.
So when do you use one over the other? It is pretty simple. When you want to make a long term measurement
(days, weeks, etc.) at a fast rate you should use the datalogger. You would use this when you are looking to
measure something like long term battery drain.
If you are looking for a more short term, faster measurement you would
use the digitizer. You would use the
digitizer to measure something like inrush current.
These are a few of the great features available in our power
supplies. Please let us know if you have
any questions on these features or any of the features of our power supplies.
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