KROHNE BM 90 EN - Manual (Page 22)

22
Enter the required value for open channel flow device
being used.
e.g. Flow Device Enter
Unity 1
Rect. flume 3/2 2
Rect. weir 3/2 2
V-notch weir 5/2 3
Special 4 (Refer to Pr.44)
Parshall Flumes 5-14
The OCM flow exponent (Pr.45) has been expanded to
include 10 Parshall flume profiles. The data for the
selected flume is loaded into the flume mapping system
(Pr.44) from tables held in memory.
Size Exponent
5 : 1,2,3,24 inches 1.550
6 : 6 inches 1.580
7 : 9 inches 1.530
8 : 12 inches 1.522
9 : 18 inches 1.538
10 : 36 inches 1.566
11 : 48 inches 1.578
12 : 72 inches 1.595
13 : 96 inches 1.606
14 : 10,12,15,20,
25,30,40,50 feet 1.600
Maximum head is entered in Pr.4 and the associated
maximum flow in Pr.46. If one of the values is known, the
other can be found in the flume tables or by calculation
from
Q = KHn GPM,
where H = Inches, Q = US GPM and
K = Constant for flume size
(for imperial gallon multiply K factor by 0.8).
Pr. 45 Flow exponent (D=1)
Pr. 40 Vessel Shape (D=0)
Enter 1
Flat
bottom
Enter 2
Pyramid
bottom
Enter 3
Conical
bottom
Enter 4
Half
sphere
bottom
Enter 5
Parabolic
bottom
Enter 6
Flat
ends
Enter 7
parabolic
ends
’ 0 ’ = no volume conversion
1 = flat bottomed vessel and percentage of span
2 - 7 = standard shapes as shown below
8 = vessel linearisation (see Pr.44)
Pr. 41 Vessel Dimension H (D=0)
Pr. 42 Vessel Dimension L (D=0)
Pr. 43 Display Conversion (D=1)
Pr. 44 Linearisation (D= ==== )
Enter H where indicated above in units selected at Pr.2.
Enter L where indicated above in units selected at Pr.2.
If Pr.40 entry is between 1 - 8 then enter - full scale dis-
play
¸
100
e.g. if 100% = 2000 litres and display required in litres
then set Pr.43 to 2000 ‚ 100 = 20.
To display in any unit enter any value from ’0.001’ to
’9999’
NOTE:
Display cannot be more than 4 digits. If it is neces-
sary to measure 20,000 gallons, then display in thou-
sands of litres (or cubic metres) by dividing 20 by
100 = 0.2.
This function allows non-standard flumes and vessels to
be characterised. For full details please refer to Appendix
1, pages 39 to 40.