User Manual

2400 Series SourceMeter
®
User’s Manual Basic Source-Measure Operation 3-11
NPLC caching
NPLC caching speeds up source memory sweeps by caching A/D reference and
zero values. When NPLC caching is enabled (using the NPLC-CACHE/ENABLE
menu selection), the A/D reference and zero values will be saved for up to the 10
most recent voltage, current, and resistance measurement functions settings.
Whenever the integration rate is changed via the SPEED key, a recalled user
setup (using the SAVESETUP/RESTORE menu selection), or during a source
memory recall (either with the -MEMORY/RESTORE menu or during a source
memory sweep), NPLC caching will occur. If the integration rate is already stored
in the cache, the stored reference and zero values are recalled and used. Other-
wise, a reference and zero value are acquired and stored in the cache. If there are
already 10 NPLC values stored, the oldest one will be overwritten by the newest
one.
NOTE Auto zero should be disabled for maximum source memory sweep
speed; otherwise the cache is of little use. With auto zero enabled, new
A/D reference and zero values are taken for every reading and saved
into the cache, slowing down sweep operation. However, with auto zero
disabled, measurements may drift and become erroneous. To minimize
drift when using NPLC caching with auto zero disabled, periodically
select AUTO-ZERO/ONCE in the A/D-CTRL menu to force an immediate
auto zero update.
NPLC cache setup
Follow the steps below to enable and use NPLC caching with a source memory
sweep:
1. Press the MENU key, select A/D-CTRL, then press ENTER.
2. Select AUTO-ZERO, then press ENTER.
3. Choose DISABLE, then press ENTER to disable auto zero.
4. From the A/D CONTROLS menu, select NPLC-CACHE, then press
ENTER.
5. Select ENABLE, then press ENTER to enable NPLC caching.
6. Use the EXIT key to back out of the main menu structure.
7. Set up the source memory parameters, and run the source memory sweep.
(See
Section 10, “Performing a source memory sweep.”)