PSM1700 PsimetriQ user manual
7-1
7 Measurement options
7.1 ACQU - Acquisition options
In normal acquisition mode the window over which the
measurements are computed is adjusted to give an
integral number of cycles of the input waveform. The
results from each window are passed through a digital
filter equivalent to a first order RC low pass filter.
There are four pre-set speed options - fast, medium, slow,
and very slow – that adjust the nominal size of the
window, and therefore the update rate and the time
constant of the filter. Greater stability is obtained at the
slower speed at the expense of a slower update rate.
There is also an option to set a specific size of the window
to a value other than the preset options. In order to
synchronise to an integral number of cycles, the window
size is either reduced by up to 25% or increased as
necessary.
Note that the window is always extended to cover at least
one complete cycle of the input waveform even if this is a
longer period than the nominal update rate.
Each window can be specified as comprising a minimum
number of cycles the waveform. This extends the
measurement window for lower frequencies. The window
time consists of the longer of the selected speed and the
minimum number of cycles.
To allow for settling of the circuitry under test, there is a
programmable delay before making a measurement.
The phase measurement is usually referenced to CH1 but
can be changed to CH2. This has the result of reversing
the measured phase.