Nivus NivuFlow 750, Instruction Manual

Page: 30 / 162

Instruction Manual
NivuFlow Mobile 750
page 30 NFM 750 - rev. 03 / 27.05.2020
21.2.2 Water ultrasound
The Type CSP-V2H1 and CSP-V2U1 sensors are equipped with a horizontal crystal element
used for level measurement based on the transit time method using water-ultrasound.
The measurement uses the time between transmission and reception of an impulse being re-
flected on the water surface.
ℎ
1
=
1
2 ×
( 𝑐𝑐 × 𝑡𝑡
1
)
•
with:

h = filling level

c = sound running time

t
1
= time between transmitted and received signal
Fig. 21-6 Determined filling level
At a medium temperature of 20 °C the sound running time in water is 1480 m/s.
The temperature-dependent deviation is 0.23 % per Kelvin.
To achieve level measurements with millimetre accuracy, the medium temperature is investi-
gated permanently. The investigated temperature is used to correct the sound running time
for calculation purposes.
The fixed level value is added to the determined value h
1
. The result is the total flow level h.
21.2.3 Air-ultrasound
Level is measured via air-ultrasound from top down by using a contactless air-ultrasonic sen-
sor Type DSM-L0. This sensor is used to measure low filling levels. It must be installed exact-
ly in the centre of the channel crown (±2°) parallel to the water surface.
Analogous to the transit time method based on water-ultrasound, a signal is transmitted too.
In this case, however, the signal is sent through the air towards the water surface from where
it is reflected. The measured transit time provides the distance between sensor and water
surface and hence the filling level of the medium.
Since the air temperature may lead to deviations in the transit time the temperature is deter-
mined and will be considered during internal calculations.