Atec Micronics-PF330 - Manual (Page 2)

Portaflow 330 Technical Datasheet
2 Portaflow 330 Technical Datasheet
(Issue 2.1)
Principles of Operation
When ultrasound is transmitted through a liquid the speed at
which the sound travels is accelerated slightly when
transmitted in the same direction as the liquid flow and
decelerated slightly when transmitted against it. The difference
in time taken by the sound to travel over the same distance but
in opposite directions is therefore proportional to the flow
velocity of the liquid and can be used to calculate the flow rate.
Transit time technique
This technique is known as ‘transit time’ measurement and is
the method used by the Portaflow 330 system to calculate the
liquid flow rate. Once the flow velocity is known it is a simple
matter for the PF330 to calculate the volumetric flow.
Operating modes
The Portaflow sensors can be set to operate in one of four
modes determined mainly by the pipe diameter and the
transducer set in use. The diagram below illustrates these
modes and shows the importance of applying the correct
separation distance between the transducers to obtain the
best possible signal.
In practice, the PF330 determines the operating mode and
calculates the appropriate transducer separation distance in
response to site application data entered by the user.
Fluid flow
Fluid flow
Fluid flow
Fluid flow
U
U
U
U
D
D
D
D
Separation
Distance
Separation
Distance
Separation
Distance
Separation
Distance
Reflex mode
Reflex mode (double bounce)
Reflex mode (triple bounce)
Diagonal mode
This is the mode most commonly used.
The two transducers (U & D) are attached
to the pipe in line with each other and the
signals passing between them are reflected
by the opposite pipe wall.
The Separation Distance is calculated by
the instrument in response to entered data
concerning the pipe and fluid characteristics.
In this mode the separation distance is
calculated to give a ‘double bounce. This is
most likely to occur if the pipe diameter is
so small that the calculated reflex mode
Separation Distance would be impractical
for the transducers in use.
This illustration goes one step further to show
a ‘triple bounce situation. This would normally
apply when working with very small pipes
relative to the transducer range in use.
This mode might be selected by the
instrument where relatively large pipes are
concerned. In this mode the transducers are
located on opposite sides of the pipe but the
Separation Distance is still critical in order
for the signals to be received correctly.
This mode might be used with the standard
‘A’ & ‘B’ transducer sets but for really large
pipe installation the optional transducer set ‘D’
might be recommended.
Upstream
transducer