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Connection and operation manual
Technical changes reserved
0141 0316-152 13.05.2016
Level controller for conducting liquids
24 V OEM-version without housing
In liquid reservoir, four electrodes (E1..E4) are mounted in the medium, at heights corresponding to the required switching point. A fifth
electrode is placed at the bottom of the reservoir (not shown in sketch) which works as the reference electrode.
According to water contact, the fill level is indicated through 4 green LED´s L1 to L4. If the reservoir is completely empty, the red LED glows.
For example, the lower pair of electrodes (E1, E2) can be used to control a filling valve at the inlet. After release of the lowest electrode E1,
the filling valve is switched ON and switched OFF again on wetting of the second electrode E2 (Hysteresis).
For example, the upper pair of electrodes can be used to control a drain valve or a pump. During contact with the topmost electrode E4, the
drain valve is switched ON and again switched OFF after release of the lower electrode E3 (Hysteresis).
The switching behaviour of the system (Filling/Empty) is to be configured over two jumper plugs. The sensitivity of the electrodes can be
adjusted through potentiometers (approx. 15 k...80 kΩ).
2.2
Operating sequence diagram
Initial condition:
The reservoir is first empty.
The electrode E1
is not in water contact.
Relay 1
is in closed position (because of this
e.g. the inlet valve is open). The water level rises in the reservoir. Water contact with the lower
Electrode E1
(1) does not change the
relay status and only when
Electrode E2
comes into water contact (2),
Relay 1
switches OFF (as an effect e.g. the inlet valve closes).
Upper level:
If the level in the reservoir continues to rise further and reaches
Electrode E3
,
Relay 2
still remains in off state. After the wa
-
ter level reaches
Electrode E4
(4),
Relay 2
is switched ON (and with that e.g. the outflow pump). When the level falls and
Electrode E4
is released free (5), the relay remains closed until
Electrode E3
is released free. (6). This means that between the upper switching ON
point
E4
and the lower switching OFF point
E3
, there is a hysteresis gap.
Lower level:
If the level continues to fall, the
Electrode E2
becomes free (7). In the reducing level direction,
Relay 1
is kept in off state,
till
Electrode E1
is also out of water contact (8). Only then
Relay 1
closes. If again the water level is in rising direction,
Relay 1
remains
closed even after water contact with
Electrode E1
(9). Only if
Electrode E2
again comes under water contact,
Relay 1
is switched OFF
(10). Hence, the lower level also has a provision of hysteresis margin.
The referred appliances “Inlet valve“ or “Pump“ are taken only as examples for illustration of the working principle. What appliances are
used finally depends on the application. The switching behaviour of both the relays can be reversed through two jumper connections.
The two relay circuits work as level regulators and are independent of each other. Hence, it is not necessary to use both the circuits, the
device is also suitable for controlling only one level. For this purpose, only two sensing electrodes and a reference electrode are required.
In such a case, the second channel (relay and electrode inputs) is not used.
B+B Thermo-Technik GmbH | Heinrich-Hertz-Straße 4 | D-78166 Donaueschingen
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