NT217 C GB1
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1-1
– Principle of measurement:
The principle of measurement is detailed and commented on in our training manual NT
106.
To summarize, note that it bears on the velocity difference (and therefore the ultrasound
wave transit times) in a moving medium, depending on whether the movement is with or
against the current.
To achieve this, it is necessary to establish dialogue between two sensors using an L-
shaped route whose projection D on the control axis is sufficient, and to measure
alternatively the route times T
1>2
and T
2>1
.
The time measurement, combined with knowledge of the geometry parameters (diameter /
thickness of pipe / L / D) allows the volume flow rate to be calculated whatever the
developments of the product, its temperature or its pressure.
Precision is even better when the Delta T measurement resolution increases (0.01
nanosecond for MiniSonic) and when the geometrical parameters are controlled, not to
forget considerations of a hydraulic order (straight lengths, flow configurations, zero setting)
or the frequency of the probes.
An order of magnitude of this Delta T in nanoseconds can be obtained simply by
multiplying the flow velocity (V in m/s) times D (in mm) or by the diameter of the pipe (mm).
1-2
– Standard installation:
12 / 24 V
D
L
Ø i
MOD_TR/ALIM
100/230VAC
2x(4-20)
2x( )
R/S
SE / SXE_M *
SM
(SE)
Zone Ex
(Probes must be certified EEx m or
EEx ia through Ultrasafe BZ 01 barriers
after standard MiniSonic)