Section 15: Frequently asked questions
2470 High Voltage SourceMeter Instrument Reference Manual
15-10
2470-901-01 Rev. A /
May
2019
Why did my settings change?
Many of the commands in the 2470 are saved with the source or measure function that was active
when you set them. For example, assume you have the measure function set to current and you set a
value for display digits. When you change the measure function to voltage, the display digits value
changes to the value that was last set for the voltage measure function. When you return to the
current measure function, the display digits value returns to the value you set previously.
What is NPLC?
You can adjust the amount of time that the input signal is measured. Adjustments to the amount of
time affect the usable measurement resolution, the amount of reading noise, and the reading rate of
the instrument.
The amount of time is specified in parameters that are based on the number of power line cycles
(NPLCs). Each power line cycle for 60 Hz is 16.67 ms (1/60); for 50 Hz, it is 20 ms (1/50).
The shortest amount of time results in the fastest reading rate, but increases the reading noise and
decreases the number of usable digits.
The longest amount of time provides the lowest reading noise and more usable digits, but has the
slowest reading rate.
Settings between the fastest and slowest number of PLCs are a compromise between speed and
noise.
If you change the PLCs, you may want to adjust the displayed digits to reflect the change in usable
digits.
