5 - Programming the DC Source
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Power Line Cycles
After a power-on or *RST, the dc source automatically makes measurements based on a 0.00912 power
line cycles (for 60 Hz line). This results in a default measurement sample of 5 points separated by 30.4
microsecond time intervals. The easiest way to increase the data acquisition time is to increase the
number of power line cycles in the measurement. By doing this the unit automatically sets the sweep time
interval, sweep offset, and sweep points, based on sampling the maximum number of points to provide
the best noise filtering.
To change the power line cycles on which a measurement is based, use:
SENS:SWE:NPLC <n>
If your load does not draw currents with a significant noise component, use a setting of 0.00912 PLC for
fast measurements. Use a setting of 1 PLC to achieve full accuracy on the 0.5mA current range.
Measurement Samples and Time Interval
You can vary both the number of data points in a measurement sample, as well as the time between
samples. This is illustrated in figure 5-2.
SENS:SWE:POIN
<
#of poi nts>
SENS:SWE:TINT
<
time
>
Figure 5-2. Commands that Control Measurement Time
When the instrument is turned on and at *RST, the output voltage or current sampling rate is 30.4
microseconds, and the sweep size is set to 5 data points. This means that it takes about 152 microseconds
per measurement. You can vary this data sampling rate with:
SENS:SWE:TINT <sample period>
SENS:SWE:POIN <points>
For example, to set the time interval to 60.8 microseconds per measurement with 1500 samples, use
SENS:SWE:TINT 60.8E-6;POIN 1500.
Note that increasing the number of sample points increases the accuracy of the measurement; however,
the tradeoff is it takes a longer time to make the measurement.
NOTE: The total number of data points cannot exceed 4096. This means that the count
multiplied by the points in each measurement cannot exceed 4096; otherwise an error
will occur.