ULTRA 4 INSTRUCTION MANUAL 
 
96 
Example 3 BS3680 Rectangular Weir    
 
 
In this example, it is required to calculate to the flow through a BS3680 
Rectangular weir. Absolute calculation will be used, and there is a 
requirement for an alarm to indicate a high flow condition to be set to relay 
3.  The flow rate is required to be displayed in litres/minute and the totaliser 
is to record the flow in cubic metres, the resettable totaliser is to be 
displayed during RUN.  
The distance from the end of the transducer horn to zero flow (P105) is 1 
metre and max head (P704) is 0.4 metres, maximum flow (P705).  
Approach width (Dim “A”) P710 = 0.5 m (1.64 ft)                         
Crest width (Dim “B”) P711   = 0.3 m (0.98 ft)                              
Crest Height (Dim “C”) P712      = 0.3 m (0.98 ft)