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1. The default Q is determined by dividing the Mass by the area between
a line drawn between Pre- and Post- BG-ECT area between the break-
through curve and the line drawn between Pre- and Post- BG-ECT. The
Uncertainty is the standard deviation of Pre- and Post- BG ECT points
multiplied by the elapsed time, divided by the Area.
Figure 9. A & B
Figure A) shows the BG ECT Regression line with too many BG N points (15) which captures some
of the rise in BGECT for CH1. After reducing the BG N (by Push-holding on the Adj. Pre- BG ECT
selection) to 5 points, the regression line is more reasonable and “snaps” on to the Post- BG ECT
sample, thereby greatly reducing the Unc on Ch1. When this Snapping event happens, the QiQuac
will double “Quack” and the “Un1:” will change to “Un1=”
2. The setting for Setup>Meta Settings>Show BGECT Line will determine if
the regression line will be shown. The setting for “Use Regression Line”
will determine if the regression line is used for determination of Uncer-
tainty. When using the regression line for uncertainty, the uncertainty is
determined as the standard error about the displayed regression line.
When the uncertainty for a channel drops below the setting for “BGECT
Reg.Snap Tol%” the regression line will switch from only using the Pre-
BGECT to using both Pre- and Post- BGECT. This will cause the regression
line to always pass through the Pre- and Post- samples. This will have a
tendency to underestimate the uncertainty.
3. If Use 3rd U/S Probe is set for a given channel, then Ch2 will be trans-
posed to that channel by x (determined by Transit Time) and y (deter-
mined by the difference between the time shifted 3rd U/S probe and the
channel Pre-BG ECT. This means the 3rd U/S Probe BGECT will always start
at the end of the Pre-BGECT sample period, as shown in Figure B) The raw
data for this plot is shown in Figure A)
The 3rd U/S Probe has the potential to greatly reduce the amount of salt
required to achieve Grade A measurements (default is <7% uncertainty).
However, it can be complicated to properly shift the Ch2 data to down-
stream sites. If you have a T-HRECS TM7.2XX probe with a Signal Injection
button, you can accurately set the injection time from the U/S site. Push
and hold the button to send an ECT of -100 to the QQ, which will be inter-
preted as an injection. It’s also possible to toggle the Use 3rd U/S Probe
value and see the difference in Q.
Figure 10: 3rd U/S Probe
In A) we see the unprocessed data from 3 channels, with Ch2 being further upstream above the
point of injection. In order to simulate a changing BGECT, we injected an unknown amount of salt
much further upstream. We then injected a known amount of salt downstream of the 3rd U/S Probe.
The Ch2 probe is always dotted and does not show the smaller pulse. The user must first set the
Pre-BGECT for both Ch0 and Ch1 as close to the rise of the pulse as possible. Push the Signal Injec-
tion button to set the CH2 injection time. This can be adjusted using Adj Pre-BG_ECT. The CH2D
display mode will shift both CH0 and CH1 backwards in time (to the left) by the calculated transit
time. The CH0S or CH1S display mode will shift the the CH2 signal forward in time by transit time.
A)
A)
B)
B)
Full Peak
(not truncated
by Adj, Y-axis)
10g net area
BG Area
CH 1 D/S
CH 0 D/S
CH 2 U/S
