PSM1700 PsimetriQ user manual
15-2
The single harmonic and the thd are expressed relative to
the fundamental either as a percentage or in dB, as
selected via the HARM menu.
PsimetriQ can operate either in real time mode at a single
frequency where the measurements are filtered and
updated on the display; or it can sweep a range of
frequencies and present the results as a table or graphs.
The frequency points to be measured are specified with
three parameters:
number of steps
start frequency
end frequency
PsimetriQ computes a multiplying factor that it applies to
the start frequency for the specified number of steps. Note
that due to compound multiplication it is unlikely that the
end frequency will be exactly that programmed. The
frequency sweep is initiated by the START key, and when
completed the data can be viewed as a table or graphs or
printed out.
The window over which the measurements are computed
is adjusted to give an integral number of cycles of the
input waveform. In real time mode the results from each
window are passed through a digital filter equivalent to a
first order RC low pass filter; in sweep mode each result
comprises a single window without any filtering.
Very good results can be obtained in a reasonable time
using the medium speed setting (e.g. 50 points x ~1/3s
17s); for the very best results, use the slow setting (50
points x ~2.5s 125s or 2 minutes, 5 seconds).
The ZOOM function can be used to select up to four
parameters from the display when in real time mode. It
has no function following a sweep.
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