NES
page 8
NES K05/0922
7.3 NE-304 Electrode Relay
The NE-304 electrode relay is a double relay with two
separated electrode circuits and one reference electrode. It
is supplied with a quiescent current relay, i.e., the relay
picks up (contact 3-4 and 6-7 close) when auxiliary power is
applied. If the electrodes are wetted or the power fails, the
relay disengages (contact 4-5 and 7-8 close). The signal
lamps (red LED`s) are energised when the relay picks up.
Electrode connection
Usage as Min./Max. switch (3 electrodes
)
Connect the ground or reference electrode to terminal 10.
Connect Min.-switching electrode to terminal 12 and the Max.-switching
electrode to terminal 15.
Level
Relay
LED
Min-
electrode
Reaches or above the switching electrode
relay drops out, contact 4-5 closed
out
Below the switching electrode
relay picks up, contact 3-4 closed
on
Max.-
electrode
Reaches or above the switching electrode relay drops out, contact 7-8 closed
out
Below the switching electrode
relay picks up, contact 6-7 closed
on
Usage as two interval controls (5 electrodes)
Connect the ground or reference electrode (longest rod) to terminal 10.
Pump 1: Connect the Max.-switching electrode to terminal 12 and the Min.-
switching electrode to terminal 13. Contact 3-4 is closed when the tank is
empty (LED 1-on). When the liquid reaches the Max. electrode, the relay
changes over and contact 4-5 closes (LED 1-out). The relay remains changed
over until the level falls below the Min. electrode. The interval then repeats
itself.
Pump 2: Connect the Max.-switching electrode to terminal 15 and the Min.-
switching electrode to terminal 16. Contact 6-7 is closed when the tank is
empty (LED 2-on). When the liquid reaches the Max. electrode, the relay
changes over and contact 7-8 closes (LED 2-out). The relay remains changed
over until the level falls below the Min. electrode. The interval then repeats
itself.
The changeover contact may be used for evacuating or filling—as shown in
the circuit examples.
