S530/S540 KTE Linear Parametric Test Library (LPTLib) User's Manual
Section 2: Linear Parametric Test Library
S530-900-01 Rev. E / September 2017
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All sources have default limits, but you can change limit values with the
limit
X
command.
When there are active sources in a test sequence, you can reset all source levels to the default of 0.0
with the
devclr
command. This resets the source level only. If a limit or any other instrument setting
has been changed from its default, it is not reset by the
devclr
call.
To reset all instrument settings to their initial or default state, use the
devint
command. The
devint
command also clears all sources by internally calling the
devclr
command before resetting all
instruments to default settings.
Ranging
The default mode of operation for all instruments is to automatically select the best range available for
sourcing and for measuring. This is known as autoranging. For sources, the range is picked when the
source value is changed. When measuring, the instrument may need to make several measurements,
each on a different range, until it finds the best range for the measurement.
Autoranged measurements can take much longer to make than fixed-range measurements because
the instrument may need to change ranges and make extra measurements before finding the correct
range. There are two features that instruments may support that improve the performance of
autoranged measurements. These are smart ranging and sticky ranging.
Smart ranging
An instrument without smart ranging successively upranges or downranges until the correct range is
found. For instruments with many ranges, a large change in signal causes the instrument to scan
through many ranges before finding the correct one. With smart ranging, the instrument uses the
measured value on the incorrect range to try and determine what the correct range will be. If the
measurement is really small, the instrument skips ranges and tries to downrange directly to the
correct range.
When upranging, the instrument upranges once. If it is still on the wrong range it goes straight to its
highest allowable range (source limits affect the highest allowable range). If this range is too large, it
uses the smart method of downranging to the correct range. Note that as instrument technologies
evolve, new instruments may actually use variations of this technique.
Sticky ranging
The other special ranging feature an instrument may have is sticky ranging. Often an instrument is
required to make many measurements on the same range. If the instrument starts on the default
range each time (for example, the highest allowable range) and goes through its autorange algorithm
for each requested measurement, the instrument must make extra measurements to get to the
correct range each time.
Sticky ranging causes the instrument to stay on the last range it was on. If the next measurement it
must make is on this range, the instrument only makes one measurement. This feature is most useful
during sweeps where most of the measurements are on the same range. Sticky ranging also
coordinates with fixed ranging. When an instrument is put on a fixed range and then switched back to
autorange, the instrument starts autoranging on that range.