AQ M-Tech AB Ultrasound Controller Manual 21
The WR-technique measures small signal changes and is therefore sensitive to small
displacements of the Level Switch. So the Level Switch must be steadily attached. Ideally the
Level Switch RS is glued with silicone sealant. Level Switch MK is not recommended for use with
the WR-technique since it is not easy to mount steadily. The WR-technique may also detect drops
of liquids lingering on the inside of the wall and falsely indicate them as liquid. There is also
sensitivity to temperature changes. The advantages of the WR-technique is independecy of liquid
sound-properties and independency of bubbles and no need for a reflecting surface.
Dual Technique
The dual technique is intended for Level Switch MK. It uses two level switches MK to measure a
single level. The two Level Switches are placed on each side of the container opposite to each
other. Ultrasound is transmitted from the one Level Switch to the other. Ultrasound will only travel
once through the liquid so the received ultrasound will be stronger than when the echo technique
is used. The large amount of silicone inside a Level Switch MK creates troublesome internal
echoes, which on a container with diameter 40mm or less may interfere with the measured echo.
Using two Level Switch MK avoids this problem and therefore achieves more reliable result. So
especially on small diameter containers it is a more reliable technique. The two Level Switches
that are to be used with dual technique should be connected as level switch 1 and level switch 2
and level switch 1 should be set to Type:MK Technique:Dual and Level Switch 2 set to No Level
Switch. Two other Level Switches can also be connected as level switch 3 and level switch 4.
Level Switch 3 should then be set to Type:MK Technique:Dual and Level Switch 4 set to No Level
Switch.
Mounting the Level Switch
Between the Level Switch and the container there must be a tight ultrasound-connection. For Level
Switch MK, this is achieved with its soft silicone surface. For the other Level Switches, it is achieved
by using silicone sealant or HTC-compound.
Mounting Level Switch MK
For attaching the Level Switch MK no glue or compound is needed. The Level Switch MK has a
flexible surface which acieves a good ultrasound-connection when it is pressed against the
container. The pressure needs to be around 15N (minimum 5N and maximum 50N), depending also
on the shape of the container. The pressure makes the flexible surface adapt to the container. It is
important the Level Switch MK is held in place with a fixture. The fixture should provide the means
for applying the pressure on the Level Switch so it will be pressed against the container. Since the
Level Switch MK has a rounded surface, the fixture need also to hold the Level Switch MK straight
in place. A possible fixture is a plastic block adapted to the shape of the container, with a 25,1mm
hole for the Level Switch. More information about how the Level Switch MK can be used for
measuring is available in Level Switch manual.
Mounting Level Switch KS / KSF / RS / RSF / CF / LS / LSF
Gluing the Level Switch is the best attachment technique. Transparent silicone sealant is highly
heat-resistant and is a very good glue. A Level Switch glued with silicone sealant is easy to remove.
The silicone sealant can for instance be Loctite 5366 or similar. Searching for silicone sealant on
google usually gives a lot of search results. Sanitary silicone sealant is however best to avoid due
to its content of fungicides which may be poisonous. Silicone takes a few days to cure but the Level
Switch can be used while the silicone is curing. Put some silicone sealant on the container-facing
side of the Level Switch and press it on to the container. The silicone should completely cover the
gap between the Level Switch and the container. During the first hours, the Level Switch must be
held securely in place with some tape or a clamp.
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