KROHNE BM 70 A_P EN - Manual (Page 43)

Installation and operating instructions BM 70 A/P Page: 43 11/00
8.5.2 Volume measurement (example)
•
In order to be able to measure volume with
the BM 70 A/P, a conversion table (volume
table) needs to be compiled with the PC-
CAT program (see Sect. 8.12).
• By means of the volume table, various
levels are allocated to specific volumes
previously calculated or measured out.
• In the case of non-sy mmetrical tanks, e.g.
tanks with dished bottom, the accuracy of
volume measurement will depend on the
number of set "level/volume pairs". The
maximum number of pairs (points) that can
be set is 50; the volume is linearly
determined (interpolated) between 2 points.
•
In the following example, 4 data pairs have
been progra mmed.
Volume table Unit volume (Fct. 3.2.3): m
3
Set table (PC-CAT): Point Level Volume
Œ
0.00 m 0.25 m³
•
0.25 m 0.70 m³
Ž
0.50 m 1.40 m³
•
5.30 m 16.80 m³
Tank height (Fct. 3.1.1): 6.00 m
Antenna extension (Fct. 3.1.6): 0.20 m
Block distance (Fct. 3.1.2): 0,70 m
Response threshold, maximum measurable level = 5.30 m, equivalent to a volume of 16.80 m ³
(calculated from lower reference point)
= tank height - block distance
(Fct. 3.1.1) (Fct. 3.1.2)
= 6,00 m - 0,70 m
Current output I Function I (Fct 3.3.1): CONVERSION
Range I (Fct. 3.3.2): 4 - 20 mA
Scaling 4 mA (Fct. 3.3.3): 0.00 m 3 , corresponds to 4 mA
Scaling 20 mA (Fct. 3.3.4): 16.80 m 3 , corresponds to 20 mA
Switching output Function S (Fct. 3.6.1): LEVEL
Type S (Fct. 3.6.2): LOW (=if level drops below threshold )
Threshold(Fct. 3.6.3): 5.00 m
Hysteresis (Fct. 3.6.4) 0.10 m
Display Function, display (Fct. 3.2.1): CONVERSION
Unit, conversion (Fct. 3.2.2): m 3 (cubic meter)