11
Installation and Operating Manual
IP277, Rev DA
Mobrey MCU200 Series
February 2020
This selects the relay change which is subject to the time delay selected on the top
switches. When the No.5 green switch is set to the right, the delay occurs between the
sensor changing state and the relay de-energising or becoming “not energised” (NE).
This time delay is a minimum of 0.5 seconds, (achieved by switching the top BROWN
switch to the right) and is used to prevent relay chatter at the changeover point. Longer
time delays are selected on the top three slide switches as follows:
The relay change in the opposite direction is immediate (within 50 milliseconds).
c.
Switch number 4.
Only one of the GREEN or RED LEDs will be illuminated at any one time. These LEDs
show the state of the MCU200 output relay.
The RED LED is labelled “ALARM” and the GREEN LED is labelled “NORMAL”.
The Switch 4 slide switch (Number 4) determines which LED will be illuminated when
the relay is energised (E). It is usual to have the GREEN/NORMAL condition occur with
the relay energised, i.e. with switch number 4 to the right (E=GREEN).
Figure 6. Example time delays for state changes
A. 2 seconds.
B. 8 seconds.
C. 30 seconds.
4.
Applications
4.1
Gain adjustment
Correct adjustment of the gain is essential for proper operation of any ultrasonic sensor system.
The HI/LO switch and potentiometer adjusts the gain of the amplifier feedback in the control
unit, which produces oscillation of the sensor when the coupling between the ultrasonic crystals
is sufficient. Therefore, the higher the gain setting, the lower the coupling needed to produce an
oscillating sensor.
The MCU201 and MCU203 operate with many Mobrey gap sensors. Correct settings for a
particular sensor and application should be found on-site by experiment, if possible. This
approach takes account of particular site conditions like RF coupling between extension cables,
which can affect the maximum allowed gain.
Other liquid characteristics, such as the presence of suspended solids or air bubbles, can mean
that the control unit gain must be set as high as possible for reliable operation. This can
overcome future solids build-up, but it should be at least one potentiometer division below the
maximum allowed level to ensure temperature and component-ageing stability. With sludge
1
2
3
1
2
3
1
2
3
A
B
C
