APPENDIX II
GLOSSARY
Aeration: - air gap between nappe and weir.
Beam angle: - angle between the opposing one-half power
limits (-3dB) of the sound beam
Blanking: - zone in which received echoes are ignored.
Crest: - the edge (sharp-crested weir) or surface
(broad crested weir) over which the flow
passes.
EEPROM: - electrically erasable programmable read
only memory.
EPROM: - erasable programmable read only memory.
Flume: - a 3 part hydraulic structure, consisting of
converging, throat and diverging sections, to
constrict the flow through the throat, thereby
increasing the head in the converging sec-
tion. The change in head is proportional to
the change in flow.
Free flow: - downstream liquid level is low enough or the
discharge flow is fast enough, so as not to
impede flow through the flume or weir.
Gauge well: - same as stilling well.
Head: - liquid level above zero (static) reference
level.
LCD: - liquid crystal display.
Max. head: - head at max. flowrate.
Measurement: - each time a transmit pulse or set number of
pulses is sent to the transducer.
Nappe: - the jet of liquid leaving the weir crest.
OCM: - open channel measurement
Primary measuring device: - hydraulic structure of a open channel for
measuring liquid flow. e.g. weirs and flumes.
Pl-399 10 – 2
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