2. Site selection & sensor installation
When selecting a suitable site to measure flow and mount the
instrument, you must consider the following:
MINIMUM STRAIGHT PIPE REQUIREMENTS
FLOW
Velocity Sensor
D = Pipe Diameter
2x D Before
6x D After
Looking down stream
FLOW
Velocity Sensor
2x D After
6x D Before
Looking up stream (preferred)
FLOW
2x D After
6x D Before
D = Pipe Diameter
FLOW
2x D After
15x D Before (Straight Length)
MINIMUM STRAIGHT PIPE REQUIREMENTS - BUTTERFLY VALVE
Velocity Sensor
(Looking up stream)
Butterfly Valve
Velocity Sensor
(Looking up stream)
Butterfly Valve
FLOW
2x D After
6x D Before
Velocity Sensor
(Looking up stream)
D = Pipe Diameter
FLOW
2x D After
15x D Before (Straight Length)
Undershot Gate/Valve
MINIMUM STRAIGHT PIPE REQUIREMENTS - UNDERSHOT GATE/VALVE
Undershot Gate/Valve
Velocity Sensor
(Looking up stream)
SENSOR MOUNTING POSITION - FULL PIPE
DEPTH SENSOR MOUNTING POSITION - PARTIALLY FULL PIPE
DEPTH SENSOR MOUNTING POSITION - OPEN CHANNEL
50mm (2 inches)
NOTE: Sensor should be mounted on the side of the channel when sediment
or weed is present
Water level
Water level
50mm (2 inches)
x
0.6x
Water level
Water level
NOTE: Straight run requirements for open channels are the same as for closed
pipes. The “diameter” to use when calculating your straight run should be the
maximum depth.
HOW TO CALCULATE INSERTION MEASURMENT FOR TRANSDUCER
x
y
x+y=z
z
y
Once the insertion depth is correct, rotate the sensor so that the
grub screw at the top of the sensor shaft is accurately pointing in the
direction of the straight section of pipe. Tighten the 3/4” gland nut to
lock the sensor in place.
