KROHNE BM 70 A Installation And Operating Instructions Manual page 50

8.6.12 Empty spectrum
What is an empty spectrum ?
•
Fixed and moving internals in the tank (including
perhaps the tank wall) produce interference signals
(reflections) that can result in incorrect measurements.
•
To enable the BM 70 A/P to identify and blank out such
interference signals, the tank profile (empty spectrum)
needs to be recorded once only prior to (initial) startup.
•
For this purpose, the tank should if possible be
completely empty and all moving parts (e.g. agitators)
switched on. If these conditions cannot be met during
startup, the tank profile (empty spectrum) can also be
recorded at a later time. Until it is recorded, however,
measurements may be inaccurate.
•
Recording of the tank
measurements that are carried out by the BM 70 A/P
and stored in the form of a so-called "empty spectrum".
•
This allows the BM 70 A/P to discriminate between
constant or regularly recurring interference signals and
the actually useful or wanted signals (level). Inter-
ference signals are suppressed and only the useful
signal is processed.
•
If no appreciable interference from internals is to be
expected, recording of the empty spectrum can also be
omitted, because a partial empty spectrum (see below)
of the flange system has been stored by the factory.
Installation and operating instructions BM 70 A/P
profile involves 1000
Recording of the empty spectrum (sequence, example)
Key Displayed
→
1.0 OPERATION
↑
2 x
3.0 INSTALL.
→
3.1 BASIS.PARAM.
↑
3.5 APPLICAT.
4 x
→ ↑
3.5.2
EMPTY.SPEC.
→
ON
↑
RECORD
↵
AVERAGE
↑
MAX. VALUES
↵
TOTAL
↑
PARTIAL
↵
40000 mm
↵
WAIT
1000...0
↵
3.5.2 READY
EMPTY.SPECT.
↵
4 x
Page: 50
Description
If "9 underscores" now shown,
key in the 9-keystroke Entry
Code 1.
Partial empty spectrum already
recorded by factory
Factory-set is here AVERAGE
(= normal empty spectrum).
This setting is suitable for most
applications
(possible alternative)
Recording of the empty
spectrum over the full range.
If the tank cannot be drained
over the full range
Enter distance value down to
which the empty spectrum is to
be recorded.
Empty spectrum being
recorded.
Duration: approx. 1.5 minutes.
Countdown is from "1000" to
"0".
After 1.5 minutes.
Tank profile recorded.
Revert to measuring mode with
display of actual level,
distance or conversion.
Empty spectrum is now
stored and will be taken
into consideration for
measurements.
11/00