Siemens OCM III Instruction Manual page 54

SIMPLE EXPONENTIAL DEVICES, P3 = 0
KHAFAGI VENTURI
15 cm (6")
plan
transducer *
0
head
side
front
For rated flows under free flow conditions, the head is measured 15 cm (6") upstream
from the beginning of the converging section.
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 55