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AUTO
One of the most timesaving commands
you can use with the CNT-8X is
:INPut:LEVel:AUTO8OFF. This will
save the time it takes to determine the
trigger levels. (About 50ms/measurement
in PM6680B and PM6685, and 85ms in
PM6681.)
Display Control
The display can be switched off with the
command
DISPlay:ENABle8OFF. When you
switch off the display, the counter loses
the measurement data resolution informa
-
tion. This means that the counter always
sends all digits independently of whether
or not they are significant. This command
reduces the dead time by about 7ms.
GPIB Data Format
You can select the format of the result
sent on the GPIB using the FORMat
command. Two options exist: ASCii and
REAL. The REAL format saves a lot of
time both in the instrument and the con
-
troller for converting data. However,
when the counter uses the REAL format,
you lose the measurement data resolution
information. It sends the REAL format as
a block data element. This means that it
sends data as:
#18< 8 bytes real>.
The <8 bytes real> is a double precision
binary floating-point code according to
IEEE 488.2 / IEEE 754.
Time Measurement
Resolution
The basic time measurement resolution
can be selected by using the command
SENSe:ACQ:RES8«HIGH|LOW».
When you set the resolution to low it will
be 100ns for PM6680B and PM6685, and
80ns for PM6681. Instead of the high res
-
olution, which is 0.25ns for PM6680B
and PM6685, and 0.05ns for PM6681.
If the counter does real-time calculations
and you switch to low resolution, the
measurement dead time decreases about
0.6 to 0.9ms. If the counter does not do
real-time calculations, then it saves only
about 0.05ms per measurement cycle. If
the counter does real time calculations
with the display switched on, then you
can save up to 2ms by selecting the lower
resolution.
Automatic Interpolator
Calibration (PM6680B/85)
The time interpolation technique achieves
the high time resolution. The counter au-
tomatically calibrates these interpolators
once per measurement cycle. You can
control this automatic calibration by us
-
ing the command:
CAL:INT:AUTO8 «ON|OFF|ONCE».
When you switch calibration off, the
measurement cycle time decreases.
Disabling this calibration makes the
counter more sensitive to temperature
changes. The measurement values may
drift away, which results in a larger inac
-
curacy. However, when the instrument
has been switched on for more than 20
minutes and the ambient temperature is
stable within ± 5°C, this is no problem.
You can also easily recalibrate the
7-8 General Speed Improvements
How to Measure Fast