Parameter assignment
7.27 TVT (Time Varying Threshold) adjustment parameters (P831 to P839)
SITRANS Probe LR with mA/HART
Operating Instructions, 05/2019, A5E32337711-AC
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P837 instructs SITRANS Probe LR to learn the echo profile at that moment, and use the
learned profile instead of the default TVT curve.
Parameter
Values Description
P837
0
Off
1
*
Use "learned" TVT
2
"Learn"
If SITRANS Probe LR displays a full level, or if the reading fluctuates between a false high
level and a correct level, you can use the TVT shaper parameters P837 and P838 together
to prevent false-echo detection. They elevate the TVT in this region and de-sensitize the
receiver from any ‘base noise" caused by internal antenna reflections, nozzle echoes, or
other vessel false echoes. For more detail, see Auto false-echo suppression (Page 88).
Setup instructions for P837 and P838 follow P838.
7.27.4
P838 Auto false echo suppression distance
Allows you to set a distance within which SITRANS Probe LR will learn a new echo profile.
(Units are defined in P005.)
Values
Range
0.000 to 20.00 m (65.6 ft): max. range
Default
1.000 m
P837 and P838 setup instructions:
1.
Perform this function when the vessel is empty or nearly empty.
2.
Rotate the instrument for best signal (lowest false-echo amplitude).
3.
Determine distance from reference point to material level, and subtract 0.5 m/1.6ft.
4.
Press PROGRAM
then DISPLAY
.
5.
Select P838, key in [distance to material level minus 0.5m/1.6 ft], and press ENTER
.
6.
Select P837.
7.
Press 2 and then press ENTER
. P837 will automatically revert to 1 (use Learned
TVT) after a few seconds.
8.
Press PROGRAM
to return to RUN mode.