15
Installation and Operating Manual
IP277, Rev DA
Mobrey MCU200 Series
February 2020
Figure 9. Mobrey 402 sensor as oil/water interface
Interface detection between two similar immiscible liquids
When liquids are ultrasonically very similar e.g. paraffin and water, the procedure in the section
“Interface detection between two dissimilar liquids” on page 14
produces very little difference
between the two “false dry” points. In this case, the “reflection” method for interface detection
is used (
Figure 10 on page 16
).
If an ultrasonic beam is transmitted from one liquid to another at a suitable angle (10°), it is split
at the interface into reflected and a refracted beams, so that it does not reach the receiver
crystal. If there is no interference in the gap, but only one liquid, the beam is received and the
sensor oscillates.
The gain adjustment is made so that the gain is 3 divisions higher than the highest false dry
position obtained. Performance at the interface should then be checked.
Note that the non-oscillating state of the sensor, at the interface, also occurs throughout any
emulsion layer at the interface and when the sensor is in air.
Sensor in oil
The ultrasonic beam is attenuated and
will not reach the receiver crystal.
Sensor in water
The ultrasonic beam reaches the
receiver crystal.
Air
Oil
Air
Oil
Receiver
crystal
Transmitter
crystal
MCU200
Series
Controller
MCU200
Series
Controller
