Emerson Rosemount 3100 Series, Reference Manual, Page: 133 / 144

Reference Manual
00809-0100-4840, Rev. BA
July 2008
F-19
Rosemount 3100 Series
P045 (Target Frequency)
P045 Description
P045 sets the frequency used for transmitting an ultrasonic pulse. The
optimum frequency depends on the characteristics of the transmitter
piezoelectric crystal, which are affected by temperature.
The transmitter has a look-up table to select a frequency value to give the
highest echo strength from the prevailing conditions at the site. This operates
when P045 is set to AUTO.
Occasionally, site or transmitter conditions require a fixed frequency, not a
variable frequency. P045 is used to set a fixed frequency, but the actual
frequency value used is selected from the look-up table and the nearest to
that entered value is selected automatically.
D916 indicates the present frequency.
P048 (Threshold 1 Size)
P048 Description
Frequently there are false echoes close to the transmitter face. If they are
outside of the desired top blanking distance, the threshold may be maintained
at an artificially high level (size in %) for a programmable duration (in ms).
The programmable size is set by P048. See also P043 for the corresponding
programmable duration.
P049 (Spike Reject)
P049 Description
P049 sets the minimum duration of a valid echo signal, and is used to reject
transient electrical interference (spike) signals.
NOTE:
Spike rejection is switched-off when P049 is set to 0.
P060 (Distance Offset)
P060 Description
The Distance Offset is the distance from the Xmtr Reference Point to the
Distance Reference Point (see Figure F-7 on page F-20). It is subtracted from
the measured range to produce the final output Distance (D902).
P063 (Bottom Blanking
Distance)
P063 Description
The Bottom Blanking Distance defines the zone above the Bottom Reference
(P010) where an echo is ignored (see Figure F-7 on page F-20). This zone
eliminates echoes from false targets (e.g. pumps) uncovered as the liquid
level decreases.
P069 (Level Offset)
P069 Description
The Level Offset is the distance from the Bottom Reference (P010) to the
Tank Reference Point (see Figure F-7 on page F-20). It is added to the
measured level to produce the final output Level (D901).