KROHNE BM 70 A Installation And Operating Instructions Manual page 51

FCT. 3.5.2 EMPTY.SPEC.
Under this function the empty spectrum is activated or
deactivated, or recorded and stored. The display first gives
information as to whether the empty spectrum is currently
switched ON or OFF. You can then choose between:
•
OFF: The empty spectrum is not considered for
measurements but remains stored in the BM 70 A/P
and can be activated again at a later date.
•
ON: The empty spectrum is (again) activated and
considered for measurements.
•
RECORD: The previous empty spectrum is to be
deleted and a new one recorded.
Conditions:
- Tank must be totally or partially drained.
- All moving parts, e.g. agitators, must be switched on.
- Tank height, antenna extension, distance piece and still
well must be set correctly.
Note: where a Wave-Stick is involved
Due to an error in Firmware Version 3.00, before the
empty spectrum can be re-recorded, parameter 3.1.3
ANTENNA (see Section 8.6.3) must first be set to
STANDARD and then set to WAVE-STICK after the empty
spectrum recording has been made. If these directions are
not observed, the "SPECT.ERR" error will be indicated,
and the recording will need to be carried out again (cor-
rectly). This error has been rectified in subsequent firm-
ware version (V. 3.01 and higher), and the empty tank
spectrum can be recorded in the usual way for the Wave-
Stick.
When you select "RECORD", the procedure is as follows:
If other configuration parameters have previously been
changed, you will first be asked by "STORE YES" whether
you wish to store the data. Confirm by pressing key
The next step is a choice of the following:
•
AVERAGE
Values are averaged. This setting can be used for
most applications.
•
MAX. VALUES
Only maximum values considered when the empty
spectrum is recorded.
Of advantage in conjunction with "difficult" agitators,
for example.
If the tank is not completely drained, the empty tank
spectrum can nevertheless still be recorded up to a certain
range. In this case, select menu item PARTIAL.
•
After selecting AVERAGE or maX. VALUES, press key
↵. Then select PARTIAL or TOTAL with key ↑, as
follows.
•
If TOTAL selected, the empty-tank spectrum is
recorded over the complete range.
•
If PARTIAL selected, interrogation is carried out via the
↵ key concerning input of the distance value up to
which the empty-tank spectrum shall be recorded.
•
The tank area below the current product level is
excluded from the recording of the empty-tank spec-
trum.
•
The distance value is entered in the same unit as used
for the tank height, in the range of 0 m to tank height.
•
It is recommended to maintain a safe distance of 20 to
30 cm (8" to 12") to the actual distance.
Subsequently press key ↵ to start recording of the empty-
tank spectrum.
"WAIT" appears briefly in the display. Then countdown of
measurements from "1000" to "0". "READY" is displayed
after approx. 1.5 Minutes.
Press ↵ key 5 times to store the empty spectrum, which
will then be taken
measurements.
Recording of the empty spectrum can be aborted by
pressing key ↵ . Displayed: BREAK. Confirm by pressing
key ↵ .
The "old" empty spectrum is retained in this case.
Installation and operating instructions BM 70 A/P
↵
.
into consideration during
8.6.13 Time constant and tracking speed
Fct. 3.5.3 TIMECONST.
•
New measured values are damped (filtered) with the
time constant so as to avoid abrupt changes in
measured values and thus also in the current output I
and the display.
•
Setting range: 001 - 100 Sec (BM 70 A)
010 - 100 Sec (BM 70 P)
•
The tank bottom must supply a measurable reflection
signal, so the method cannot be applied e.g. when a
dished bottom is involved.
•
Default value and recommended setting:
010 Sec (BM 70 A)
030 Sec (BM 70 P)
Fct. 3.5.4 TRACING.VEL.
To avoid faulty measurements, the BM 70 A/P places a sy
mmetrical "plausibility range" around the last valid
measured value in which the next measured value is
expected. Measured values outside this range are identi-
fied as invalid and are suppressed.
If no valid measured value is identified, the BM 70 A/P
enlarges the plausibility range with the tracing speed (Fct.
3.5.4) until a valid (plausible) measured value has again
been found.
The measured value for level/distance cannot change at a
faster rate than the set tracing speed.
•
Under Fct. 3.5.4 the maximum rate at which the level
can change in the tank should be set as the minimum
value.
•
Setting ranges:
BM 70 A
0.01 - 10.00 m/min (if Fct. 3.1.1. Unit m/ cm/ mm)
0.03 - 32.80 ft/min (if Fct. 3.1.1. Unit inch/ft)
BM 70 P
0.01 - 1.00 m/min (if Fct. 3.1.1. Unit m/ cm/ mm)
0.03 - 3.28 ft/min (if Fct. 3.1.1. Unit inch/ft)
•
Default: 0.5 m/min (BM 70 A); 0.1 m/min (BM 70 P)
•
See also Sect. 8.8 (error message: NO M.VALUE)
8.6.14 Multiple reflections and block distance
detection
Fct. 3.5.5 MULT.REFL.
Multiple reflections frequently occur in storage tanks with
an extremely calm surface, typically when the BM 70 A/P
is mounted on a dome or centred on a "dished cover", or
the vessel is fitted with a flat or only very slightly convex
head.
Such multiple reflections tend to simulate lower-than-
actual levels. In such cases, activate the multiple
reflections identifier, and see also references in Sect. 8.8.
•
NO (default)
Measurement without identification of multiple
reflections.
•
YES
Measurement with identification of multiple reflections.
A better solution, however, is to change the mounting
location of the BM 70 A/P so as to prevent the occurrence
of multiple reflections in the first place, or at least to
diminish the strength of the multiple reflections (see Sect.
6.1.2).
To ensure satisfactory identification of the first measured
value after the BM 70 A/P has been switched on, always
carry out measurements with the "empty spectrum" (Fct.
3.5.2) when the "multiple reflection identifier" is activated,
see Sect. 8.6.12.
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