
Section 2: Linear Parametric Test Library
S530/S540 KTE Linear Parametric Test Library (LPTLib) User's Manual
2-4
S530-900-01 Rev. E / September 2017
Settling time
Another issue associated with range changes is settling time. The lowest ranges of an instrument can
have significantly larger settling times than the higher ranges. Both sticky ranging and smart ranging
help with this problem.
You may want autoranged measurements but do not care about resolution once the signal falls below
a certain value. In this case, having an autoranged measurement go to the lowest range an
instrument has wastes time.
You can use the
lorange
X
command to specify the lowest range an instrument uses when
autoranging. The instrument then gives you the resolution you need without wasting time trying to
make a measurement on a more accurate range.
Fixed ranging
Often, autoranged measurements are not required. If the range on which a measurement will be
made is known before the measurement is made, fixed ranging can be used. You can select a fixed
range on an instrument with the
range
X
command. Fixed-range measurements are made more
quickly than autoranged measurements.
When making fixed range measurements, you must be careful that the range is not set too low. If the
range is set too low, the signal may be too large to measure on the specified range. If the signal is
larger than the full scale of the range, the instrument goes into an overrange condition. When this
happens, the instrument returns a special value to indicate the error instead of the actual
measurement.
Range limits
When an instrument is on a range lower than its compliance limit, it limits at full scale of range. For
example, a voltage source that is fixed on the 10 µA current measurement range limits at 10 µA, even
though the compliance may be programmed to a larger value. Because a fixed range measurement
will not automatically uprange, it cannot resolve this artificial compliance. This is known as range limit.
This can affect measurements made on another instrument because the source is not forcing the
programmed value. The system automatically resolves problems like this, but only for instruments
that are on autorange.
Matrix operations
Most instruments require their terminals to be connected to a device under test (DUT) before they can
be used. This involves the use of matrix commands. A typical test sequence consists of making
connections, sourcing, measuring, and then calling the
devint
command to restore the entire
system, including the matrix, to its default condition.
The command most used to make connections is the
conpin
command. Normally, several
conpin
calls are made together at the beginning of a test sequence. These grouped
conpin
calls are
collectively called a conpin sequence.
If you need to clear all matrix connections in the middle of a test sequence, you can call the
clrcon
command to do this explicitly. If you start a new conpin sequence in the middle of a test sequence,
the
conpin
command automatically performs a
clrcon
command before making any new
connections.