Section 2: Linear Parametric Test Library
S530/S540 KTE Linear Parametric Test Library (LPTLib) User's Manual
2-2
S530-900-01 Rev. E / September 2017
Averaged measurements
Averaged measurements are made with the
avg
X
command. Make an averaged measurement by
making several single-point measurements and averaging them. Averaged measurements reduce the
effects of random noise.
Integrated measurements
Integrated measurements are made with the
intg
X
command. Integrated measurements examine
the signal over a longer period and reduce the effects of AC noise. Like averaged measurements,
integrated measurements reduce the effects of random noise, but they also reject noise with a period
that is an integer multiple of the integration period or aperture.
You can change the integration aperture of some instruments. Integration apertures are commonly
defined in units of power line cycles (PLCs). A PLC is the time it takes for one complete AC cycle of
the main power supplied to the system. The default integration aperture is one PLC. For 60 Hz power,
one PLC is 16.667 ms; for 50 Hz, one PLC is 20 ms. An integration aperture of 0.1 PLC on a 60 Hz
system is (0.1)(16.667 ms) = 1.667 ms.
A common mistake is to try to use large aperture integrated measurements to eliminate the effect of
random noise. Although noise can be reduced this way, it is typically more productive to use an
averaged measurement. The integrated measurement is generally as stable, but averaged
measurements usually can be made more quickly than integrated measurements.
This is especially true when making autoranged measurements. When an instrument makes
autoranged measurements, all of the measurements it makes when determining the best range are
done at the same aperture. If the instrument discards any measurements because they are on a
suboptimal range, time is wasted if they are made with a large aperture. With averaged
measurements, the instrument typically spends less time finding the optimal range.
Some instruments allow combinations of integration and averaging by allowing the behavior of one or
more of the three types of measurements to be altered temporarily. In this case, the instrument is
capable of performing an averaged integrated measurement.
Sourcing and limits
Source instruments normally force 0.0 by default. You can change the source value with the
force
X
command. All current and voltage sources restrict the complementary function to the one they are
sourcing.
Current is the complementary function of voltage, and voltage is the complementary function of
current. For example, when a voltage source is forcing voltage, it restricts how much current it allows
to flow (including when it is sourcing its default 0.0 value). This is called the limit (also known as the
compliance limit). A current limit is used for a voltage source and a voltage limit is used for a current
source.
When this limit is reached, the source reduces its force value. In the preceding example, when the
voltage source reaches the limit, it reduces the voltage being forced so that the current does not
exceed the limit. When this happens, the source is said to be in compliance. For this example, the
voltage source is in current compliance.