SFRA45 User Manual
8-1
8
Setup / Key Functions
8.1
Acquisition Mode (ACQU)
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.
Speed –
Has six pre-set speed options – “
very slow, slow,
medium, fast, very fast and window
”– it adjusts 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. Note that at low frequencies, the window is
extended to cover a complete cycle of the input waveform
even if this is a longer period than the nominal update
rate.
Filter -
Filter has three options:
“normal”, “slow” and
“none”.
This sets how many samples the instrument takes
before updating the display and effectively smoothes the
readings. If none is selected then the readings are
unfiltered and more prone to noise.
The nominal values are:
speed
update
rate
normal
time
constant
slow time
constant
fast
1/20s
0.2s
0.8s
medium
1/3s
1.5s
6s
slow
2.5s
12s
48s
very slow
10s
48s
192s
