Soft dB Tenor 24bits Data User Guide - Manual (Page 40)

Tenor Data Logger Soft dB inc.
The coherence graph allows determining if the signal measured on both channels is
linked. The equation used for the coherence is:
Coherence=H1/H2=Sxy 2 /(Sxx*Syy)
Tthe Do Graph Autoscale button allows adjusting the Y and X scales of both the FRF and
coherence graphs.
The next table explains the computation parameters:
Computation parameter Description
This is the number of lines of the average FRF.
Possible selection are 1024, 2048, 4096 or 8192 lines.
The FRF calculation is done with a block size of 2*Nbr
Lines.
This is the time window used for the Sxx, Syy and Sxy
computation.
This parameter allows adjusting the overlap between
the time blocks used for the FRF calculation. This
parameter can be adjusted from 0% to 90%. This
parameter is used to increase the number of block
used for the average calculation and to compensate
for the loss of data that causes the time window. The
classic set-up is an overlap of 66% and the Hanning
window.
The dB/Lin. parameter allows choosing the amplitude
scale format. The choices are dB or Lin.
This parameter allows selecting the Hx (H1, H2 or
H3). Refer to the beginning of this section for
computation technique detail. H1 must be used if
noise is on the second channel while H2 must be used
if noise is on the reference channel. H3 is an average
of both H1 and H2 and can be used if the noise is on
both channels.
These controls allow selecting the reference channel
(x) and the second channel (y).
User Manual p. 40