Nivus OCM F, Instruction Manual

Page: 74 / 110

Instruction Manual
OCM F
page 74 OCM F - rev. 05 / 06.04.2018
24.7 I/O submenu “v-Histogram”
The frequency histogram indicates the spreading of the investigated Doppler frequency. Each
bar (peak) represents a frequency group.
This is particularly important to assess and to choose measurement places as well as to find
a place for sensor installation.
1
Quality of velocity measurement
2
Frequency group (peak)
3
Measurement frequency
4
Currently measured flow velocity
5
Invalid values
Fig. 24-8 Distribution of frequency groups
The measurement quality (0…100 %) indicates the relation between the evaluated Doppler
frequency and the entire frequency spectrum measured. The higher the quality, the more
reliable the indicated flow velocity reading. There are no limit values for the quality (Q) since
the shape of the frequency distribution has to be considered additionally. This shape is more
important for hydraulic assessment than “Q”.
Flow velocity measurement value through poorly distributed frequency groups
There are cases where, despite comparatively high quality values, it is not possible to cor-
rectly investigate the flow velocity reading due to poor frequency group distribution. In such
cases install the flow velocity sensor in another place (see “Installation Instruction for Cor-
relation and Doppler Sensors”).
Quality = very good
Frequency distribution = very good
Quality = good
Frequency distribution = good
Quality = satisfactory
Frequency distribution = satisfactory
Quality = none
Frequency distribution = none