Keithley 2600a series, Reference Manual, Page: 79 / 696

2600AS-901-01 Rev. B / September 2008 Return to Section Topics 3-7
Series 2600A System SourceMeter® Instruments Reference Manual Section 3: Basic Operation
smua.measure.autozero = smua.AUTOZERO_AUTO
NPLC caching
NPLC caching speeds up operation by caching A/D reference and zero values for up to the ten
most recent measurement aperture settings. Whenever the integration rate is changed via the
SPEED key, or a user setup is recalled, the NPLC cache is checked. If the integration rate is
already stored in the cache, the stored reference and zero values are recalled and used.
Otherwise, a reference and zero value are acquired and stored in the cache. If there are already
ten NPLC values stored, the oldest one will be overwritten by the newest one. When auto zero is
off, NPLC values stored in the cache will be used regardless of how old they are. If there are no
entries in the cache for the aperture being used, the unit will acquire them when the first
measurement is made
Basic source-measure procedure
Front panel source-measure procedure
Use the following procedure to perform the basic source-measure operations of the Series 2600A.
The following procedure assumes that the Series 2600A is already connected to the DUT as
explained in Section 3.
WARNING Hazardous voltages may be present on the output and guard
terminals. To prevent electrical shock that could cause injury or
death, NEVER make or break connections to the Series 2600A
while the output is on. Power off the equipment from the front
panel or disconnect the main power cord from the rear of the
Series 2600A before handling cables connected to the outputs.
Putting the equipment into standby does not guarantee the outputs
are not powered if a hardware or software fault occurs.
Step 1: Select and set source level.
Perform the following steps to select the source and edit the source value:
1. Press SRC as needed to select the V-Source or I-Source as indicated by the units in the
source field on the display. The flashing digit (cursor) indicates which value is presently
selected for editing.
Table 3-5
Auto zero command and options
Command
*
Description
smuX.measure.autozero = smuX.AUTOZERO_OFF
smuX.measure.autozero = smuX.AUTOZERO_ONCE
smuX.measure.autozero = smuX.AUTOZERO_AUTO
Disable auto zero**
Force one ref and zero
Force ref and zero with each
measurement
*smuX = smua for the Model 2601A/2611A/2635A; smuX = smua (Channel A) or smub (Channel B) for the Model
2602A/2612A/2636A.
**Old NPLC cache values will be used when auto zero is disabled (see To minimize the drift, a reference and zero
measurement should be made just prior to the critical test sequence. The ONCE setting can be used to force a
refresh of the reference and zero measurements used for the current aperture setting.
).